Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 1625 insertions, 0 deletions

diff --git a/kernel/Documentation/DocBook/libata.tmpl b/kernel/Documentation/DocBook/libata.tmpl
new file mode 100644
index 000000000..d7fcdc5a4
--- /dev/null
+++ b/kernel/Documentation/DocBook/libata.tmpl
@@ -0,0 +1,1625 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
+	"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
+
+<book id="libataDevGuide">
+ <bookinfo>
+  <title>libATA Developer's Guide</title>
+  
+  <authorgroup>
+   <author>
+    <firstname>Jeff</firstname>
+    <surname>Garzik</surname>
+   </author>
+  </authorgroup>
+
+  <copyright>
+   <year>2003-2006</year>
+   <holder>Jeff Garzik</holder>
+  </copyright>
+
+  <legalnotice>
+   <para>
+   The contents of this file are subject to the Open
+   Software License version 1.1 that can be found at
+   <ulink url="http://fedoraproject.org/wiki/Licensing:OSL1.1">http://fedoraproject.org/wiki/Licensing:OSL1.1</ulink>
+   and is included herein by reference.
+   </para>
+
+   <para>
+   Alternatively, the contents of this file may be used under the terms
+   of the GNU General Public License version 2 (the "GPL") as distributed
+   in the kernel source COPYING file, in which case the provisions of
+   the GPL are applicable instead of the above.  If you wish to allow
+   the use of your version of this file only under the terms of the
+   GPL and not to allow others to use your version of this file under
+   the OSL, indicate your decision by deleting the provisions above and
+   replace them with the notice and other provisions required by the GPL.
+   If you do not delete the provisions above, a recipient may use your
+   version of this file under either the OSL or the GPL.
+   </para>
+
+  </legalnotice>
+ </bookinfo>
+
+<toc></toc>
+
+  <chapter id="libataIntroduction">
+     <title>Introduction</title>
+  <para>
+  libATA is a library used inside the Linux kernel to support ATA host
+  controllers and devices.  libATA provides an ATA driver API, class
+  transports for ATA and ATAPI devices, and SCSI&lt;-&gt;ATA translation
+  for ATA devices according to the T10 SAT specification.
+  </para>
+  <para>
+  This Guide documents the libATA driver API, library functions, library
+  internals, and a couple sample ATA low-level drivers.
+  </para>
+  </chapter>
+
+  <chapter id="libataDriverApi">
+     <title>libata Driver API</title>
+     <para>
+     struct ata_port_operations is defined for every low-level libata
+     hardware driver, and it controls how the low-level driver
+     interfaces with the ATA and SCSI layers.
+     </para>
+     <para>
+     FIS-based drivers will hook into the system with ->qc_prep() and
+     ->qc_issue() high-level hooks.  Hardware which behaves in a manner
+     similar to PCI IDE hardware may utilize several generic helpers,
+     defining at a bare minimum the bus I/O addresses of the ATA shadow
+     register blocks.
+     </para>
+     <sect1>
+        <title>struct ata_port_operations</title>
+
+	<sect2><title>Disable ATA port</title>
+	<programlisting>
+void (*port_disable) (struct ata_port *);
+	</programlisting>
+
+	<para>
+	Called from ata_bus_probe() error path, as well as when
+	unregistering from the SCSI module (rmmod, hot unplug).
+	This function should do whatever needs to be done to take the
+	port out of use.  In most cases, ata_port_disable() can be used
+	as this hook.
+	</para>
+	<para>
+	Called from ata_bus_probe() on a failed probe.
+	Called from ata_scsi_release().
+	</para>
+
+	</sect2>
+
+	<sect2><title>Post-IDENTIFY device configuration</title>
+	<programlisting>
+void (*dev_config) (struct ata_port *, struct ata_device *);
+	</programlisting>
+
+	<para>
+	Called after IDENTIFY [PACKET] DEVICE is issued to each device
+	found.  Typically used to apply device-specific fixups prior to
+	issue of SET FEATURES - XFER MODE, and prior to operation.
+	</para>
+	<para>
+	This entry may be specified as NULL in ata_port_operations.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Set PIO/DMA mode</title>
+	<programlisting>
+void (*set_piomode) (struct ata_port *, struct ata_device *);
+void (*set_dmamode) (struct ata_port *, struct ata_device *);
+void (*post_set_mode) (struct ata_port *);
+unsigned int (*mode_filter) (struct ata_port *, struct ata_device *, unsigned int);
+	</programlisting>
+
+	<para>
+	Hooks called prior to the issue of SET FEATURES - XFER MODE
+	command.  The optional ->mode_filter() hook is called when libata
+	has built a mask of the possible modes. This is passed to the 
+	->mode_filter() function which should return a mask of valid modes
+	after filtering those unsuitable due to hardware limits. It is not
+	valid to use this interface to add modes.
+	</para>
+	<para>
+	dev->pio_mode and dev->dma_mode are guaranteed to be valid when
+	->set_piomode() and when ->set_dmamode() is called. The timings for
+	any other drive sharing the cable will also be valid at this point.
+	That is the library records the decisions for the modes of each
+	drive on a channel before it attempts to set any of them.
+	</para>
+	<para>
+	->post_set_mode() is
+	called unconditionally, after the SET FEATURES - XFER MODE
+	command completes successfully.
+	</para>
+
+	<para>
+	->set_piomode() is always called (if present), but
+	->set_dma_mode() is only called if DMA is possible.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Taskfile read/write</title>
+	<programlisting>
+void (*sff_tf_load) (struct ata_port *ap, struct ata_taskfile *tf);
+void (*sff_tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
+	</programlisting>
+
+	<para>
+	->tf_load() is called to load the given taskfile into hardware
+	registers / DMA buffers.  ->tf_read() is called to read the
+	hardware registers / DMA buffers, to obtain the current set of
+	taskfile register values.
+	Most drivers for taskfile-based hardware (PIO or MMIO) use
+	ata_sff_tf_load() and ata_sff_tf_read() for these hooks.
+	</para>
+
+	</sect2>
+
+	<sect2><title>PIO data read/write</title>
+	<programlisting>
+void (*sff_data_xfer) (struct ata_device *, unsigned char *, unsigned int, int);
+	</programlisting>
+
+	<para>
+All bmdma-style drivers must implement this hook.  This is the low-level
+operation that actually copies the data bytes during a PIO data
+transfer.
+Typically the driver will choose one of ata_sff_data_xfer_noirq(),
+ata_sff_data_xfer(), or ata_sff_data_xfer32().
+	</para>
+
+	</sect2>
+
+	<sect2><title>ATA command execute</title>
+	<programlisting>
+void (*sff_exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
+	</programlisting>
+
+	<para>
+	causes an ATA command, previously loaded with
+	->tf_load(), to be initiated in hardware.
+	Most drivers for taskfile-based hardware use ata_sff_exec_command()
+	for this hook.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Per-cmd ATAPI DMA capabilities filter</title>
+	<programlisting>
+int (*check_atapi_dma) (struct ata_queued_cmd *qc);
+	</programlisting>
+
+	<para>
+Allow low-level driver to filter ATA PACKET commands, returning a status
+indicating whether or not it is OK to use DMA for the supplied PACKET
+command.
+	</para>
+	<para>
+	This hook may be specified as NULL, in which case libata will
+	assume that atapi dma can be supported.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Read specific ATA shadow registers</title>
+	<programlisting>
+u8   (*sff_check_status)(struct ata_port *ap);
+u8   (*sff_check_altstatus)(struct ata_port *ap);
+	</programlisting>
+
+	<para>
+	Reads the Status/AltStatus ATA shadow register from
+	hardware.  On some hardware, reading the Status register has
+	the side effect of clearing the interrupt condition.
+	Most drivers for taskfile-based hardware use
+	ata_sff_check_status() for this hook.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Write specific ATA shadow register</title>
+	<programlisting>
+void (*sff_set_devctl)(struct ata_port *ap, u8 ctl);
+	</programlisting>
+
+	<para>
+	Write the device control ATA shadow register to the hardware.
+	Most drivers don't need to define this.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Select ATA device on bus</title>
+	<programlisting>
+void (*sff_dev_select)(struct ata_port *ap, unsigned int device);
+	</programlisting>
+
+	<para>
+	Issues the low-level hardware command(s) that causes one of N
+	hardware devices to be considered 'selected' (active and
+	available for use) on the ATA bus.  This generally has no
+	meaning on FIS-based devices.
+	</para>
+	<para>
+	Most drivers for taskfile-based hardware use
+	ata_sff_dev_select() for this hook.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Private tuning method</title>
+	<programlisting>
+void (*set_mode) (struct ata_port *ap);
+	</programlisting>
+
+	<para>
+	By default libata performs drive and controller tuning in
+	accordance with the ATA timing rules and also applies blacklists
+	and cable limits. Some controllers need special handling and have
+	custom tuning rules, typically raid controllers that use ATA
+	commands but do not actually do drive timing.
+	</para>
+
+	<warning>
+	<para>
+	This hook should not be used to replace the standard controller
+	tuning logic when a controller has quirks. Replacing the default
+	tuning logic in that case would bypass handling for drive and
+	bridge quirks that may be important to data reliability. If a
+	controller needs to filter the mode selection it should use the
+	mode_filter hook instead.
+	</para>
+	</warning>
+
+	</sect2>
+
+	<sect2><title>Control PCI IDE BMDMA engine</title>
+	<programlisting>
+void (*bmdma_setup) (struct ata_queued_cmd *qc);
+void (*bmdma_start) (struct ata_queued_cmd *qc);
+void (*bmdma_stop) (struct ata_port *ap);
+u8   (*bmdma_status) (struct ata_port *ap);
+	</programlisting>
+
+	<para>
+When setting up an IDE BMDMA transaction, these hooks arm
+(->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop)
+the hardware's DMA engine.  ->bmdma_status is used to read the standard
+PCI IDE DMA Status register.
+	</para>
+
+	<para>
+These hooks are typically either no-ops, or simply not implemented, in
+FIS-based drivers.
+	</para>
+	<para>
+Most legacy IDE drivers use ata_bmdma_setup() for the bmdma_setup()
+hook.  ata_bmdma_setup() will write the pointer to the PRD table to
+the IDE PRD Table Address register, enable DMA in the DMA Command
+register, and call exec_command() to begin the transfer.
+	</para>
+	<para>
+Most legacy IDE drivers use ata_bmdma_start() for the bmdma_start()
+hook.  ata_bmdma_start() will write the ATA_DMA_START flag to the DMA
+Command register.
+	</para>
+	<para>
+Many legacy IDE drivers use ata_bmdma_stop() for the bmdma_stop()
+hook.  ata_bmdma_stop() clears the ATA_DMA_START flag in the DMA
+command register.
+	</para>
+	<para>
+Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status() hook.
+	</para>
+
+	</sect2>
+
+	<sect2><title>High-level taskfile hooks</title>
+	<programlisting>
+void (*qc_prep) (struct ata_queued_cmd *qc);
+int (*qc_issue) (struct ata_queued_cmd *qc);
+	</programlisting>
+
+	<para>
+	Higher-level hooks, these two hooks can potentially supercede
+	several of the above taskfile/DMA engine hooks.  ->qc_prep is
+	called after the buffers have been DMA-mapped, and is typically
+	used to populate the hardware's DMA scatter-gather table.
+	Most drivers use the standard ata_qc_prep() helper function, but
+	more advanced drivers roll their own.
+	</para>
+	<para>
+	->qc_issue is used to make a command active, once the hardware
+	and S/G tables have been prepared.  IDE BMDMA drivers use the
+	helper function ata_qc_issue_prot() for taskfile protocol-based
+	dispatch.  More advanced drivers implement their own ->qc_issue.
+	</para>
+	<para>
+	ata_qc_issue_prot() calls ->tf_load(), ->bmdma_setup(), and
+	->bmdma_start() as necessary to initiate a transfer.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Exception and probe handling (EH)</title>
+	<programlisting>
+void (*eng_timeout) (struct ata_port *ap);
+void (*phy_reset) (struct ata_port *ap);
+	</programlisting>
+
+	<para>
+Deprecated.  Use ->error_handler() instead.
+	</para>
+
+	<programlisting>
+void (*freeze) (struct ata_port *ap);
+void (*thaw) (struct ata_port *ap);
+	</programlisting>
+
+	<para>
+ata_port_freeze() is called when HSM violations or some other
+condition disrupts normal operation of the port.  A frozen port
+is not allowed to perform any operation until the port is
+thawed, which usually follows a successful reset.
+	</para>
+
+	<para>
+The optional ->freeze() callback can be used for freezing the port
+hardware-wise (e.g. mask interrupt and stop DMA engine).  If a
+port cannot be frozen hardware-wise, the interrupt handler
+must ack and clear interrupts unconditionally while the port
+is frozen.
+	</para>
+	<para>
+The optional ->thaw() callback is called to perform the opposite of ->freeze():
+prepare the port for normal operation once again.  Unmask interrupts,
+start DMA engine, etc.
+	</para>
+
+	<programlisting>
+void (*error_handler) (struct ata_port *ap);
+	</programlisting>
+
+	<para>
+->error_handler() is a driver's hook into probe, hotplug, and recovery
+and other exceptional conditions.  The primary responsibility of an
+implementation is to call ata_do_eh() or ata_bmdma_drive_eh() with a set
+of EH hooks as arguments:
+	</para>
+
+	<para>
+'prereset' hook (may be NULL) is called during an EH reset, before any other actions
+are taken.
+	</para>
+
+	<para>
+'postreset' hook (may be NULL) is called after the EH reset is performed.  Based on
+existing conditions, severity of the problem, and hardware capabilities,
+	</para>
+
+	<para>
+Either 'softreset' (may be NULL) or 'hardreset' (may be NULL) will be
+called to perform the low-level EH reset.
+	</para>
+
+	<programlisting>
+void (*post_internal_cmd) (struct ata_queued_cmd *qc);
+	</programlisting>
+
+	<para>
+Perform any hardware-specific actions necessary to finish processing
+after executing a probe-time or EH-time command via ata_exec_internal().
+	</para>
+
+	</sect2>
+
+	<sect2><title>Hardware interrupt handling</title>
+	<programlisting>
+irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
+void (*irq_clear) (struct ata_port *);
+	</programlisting>
+
+	<para>
+	->irq_handler is the interrupt handling routine registered with
+	the system, by libata.  ->irq_clear is called during probe just
+	before the interrupt handler is registered, to be sure hardware
+	is quiet.
+	</para>
+	<para>
+	The second argument, dev_instance, should be cast to a pointer
+	to struct ata_host_set.
+	</para>
+	<para>
+	Most legacy IDE drivers use ata_sff_interrupt() for the
+	irq_handler hook, which scans all ports in the host_set,
+	determines which queued command was active (if any), and calls
+	ata_sff_host_intr(ap,qc).
+	</para>
+	<para>
+	Most legacy IDE drivers use ata_sff_irq_clear() for the
+	irq_clear() hook, which simply clears the interrupt and error
+	flags in the DMA status register.
+	</para>
+
+	</sect2>
+
+	<sect2><title>SATA phy read/write</title>
+	<programlisting>
+int (*scr_read) (struct ata_port *ap, unsigned int sc_reg,
+		 u32 *val);
+int (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
+                   u32 val);
+	</programlisting>
+
+	<para>
+	Read and write standard SATA phy registers.  Currently only used
+	if ->phy_reset hook called the sata_phy_reset() helper function.
+	sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.
+	</para>
+
+	</sect2>
+
+	<sect2><title>Init and shutdown</title>
+	<programlisting>
+int (*port_start) (struct ata_port *ap);
+void (*port_stop) (struct ata_port *ap);
+void (*host_stop) (struct ata_host_set *host_set);
+	</programlisting>
+
+	<para>
+	->port_start() is called just after the data structures for each
+	port are initialized.  Typically this is used to alloc per-port
+	DMA buffers / tables / rings, enable DMA engines, and similar
+	tasks.  Some drivers also use this entry point as a chance to
+	allocate driver-private memory for ap->private_data.
+	</para>
+	<para>
+	Many drivers use ata_port_start() as this hook or call
+	it from their own port_start() hooks.  ata_port_start()
+	allocates space for a legacy IDE PRD table and returns.
+	</para>
+	<para>
+	->port_stop() is called after ->host_stop().  Its sole function
+	is to release DMA/memory resources, now that they are no longer
+	actively being used.  Many drivers also free driver-private
+	data from port at this time.
+	</para>
+	<para>
+	->host_stop() is called after all ->port_stop() calls
+have completed.  The hook must finalize hardware shutdown, release DMA
+and other resources, etc.
+	This hook may be specified as NULL, in which case it is not called.
+	</para>
+
+	</sect2>
+
+     </sect1>
+  </chapter>
+
+  <chapter id="libataEH">
+        <title>Error handling</title>
+
+	<para>
+	This chapter describes how errors are handled under libata.
+	Readers are advised to read SCSI EH
+	(Documentation/scsi/scsi_eh.txt) and ATA exceptions doc first.
+	</para>
+
+	<sect1><title>Origins of commands</title>
+	<para>
+	In libata, a command is represented with struct ata_queued_cmd
+	or qc.  qc's are preallocated during port initialization and
+	repetitively used for command executions.  Currently only one
+	qc is allocated per port but yet-to-be-merged NCQ branch
+	allocates one for each tag and maps each qc to NCQ tag 1-to-1.
+	</para>
+	<para>
+	libata commands can originate from two sources - libata itself
+	and SCSI midlayer.  libata internal commands are used for
+	initialization and error handling.  All normal blk requests
+	and commands for SCSI emulation are passed as SCSI commands
+	through queuecommand callback of SCSI host template.
+	</para>
+	</sect1>
+
+	<sect1><title>How commands are issued</title>
+
+	<variablelist>
+
+	<varlistentry><term>Internal commands</term>
+	<listitem>
+	<para>
+	First, qc is allocated and initialized using
+	ata_qc_new_init().  Although ata_qc_new_init() doesn't
+	implement any wait or retry mechanism when qc is not
+	available, internal commands are currently issued only during
+	initialization and error recovery, so no other command is
+	active and allocation is guaranteed to succeed.
+	</para>
+	<para>
+	Once allocated qc's taskfile is initialized for the command to
+	be executed.  qc currently has two mechanisms to notify
+	completion.  One is via qc->complete_fn() callback and the
+	other is completion qc->waiting.  qc->complete_fn() callback
+	is the asynchronous path used by normal SCSI translated
+	commands and qc->waiting is the synchronous (issuer sleeps in
+	process context) path used by internal commands.
+	</para>
+	<para>
+	Once initialization is complete, host_set lock is acquired
+	and the qc is issued.
+	</para>
+	</listitem>
+	</varlistentry>
+
+	<varlistentry><term>SCSI commands</term>
+	<listitem>
+	<para>
+	All libata drivers use ata_scsi_queuecmd() as
+	hostt->queuecommand callback.  scmds can either be simulated
+	or translated.  No qc is involved in processing a simulated
+	scmd.  The result is computed right away and the scmd is
+	completed.
+	</para>
+	<para>
+	For a translated scmd, ata_qc_new_init() is invoked to
+	allocate a qc and the scmd is translated into the qc.  SCSI
+	midlayer's completion notification function pointer is stored
+	into qc->scsidone.
+	</para>
+	<para>
+	qc->complete_fn() callback is used for completion
+	notification.  ATA commands use ata_scsi_qc_complete() while
+	ATAPI commands use atapi_qc_complete().  Both functions end up
+	calling qc->scsidone to notify upper layer when the qc is
+	finished.  After translation is completed, the qc is issued
+	with ata_qc_issue().
+	</para>
+	<para>
+	Note that SCSI midlayer invokes hostt->queuecommand while
+	holding host_set lock, so all above occur while holding
+	host_set lock.
+	</para>
+	</listitem>
+	</varlistentry>
+
+	</variablelist>
+	</sect1>
+
+	<sect1><title>How commands are processed</title>
+	<para>
+	Depending on which protocol and which controller are used,
+	commands are processed differently.  For the purpose of
+	discussion, a controller which uses taskfile interface and all
+	standard callbacks is assumed.
+	</para>
+	<para>
+	Currently 6 ATA command protocols are used.  They can be
+	sorted into the following four categories according to how
+	they are processed.
+	</para>
+
+	<variablelist>
+	   <varlistentry><term>ATA NO DATA or DMA</term>
+	   <listitem>
+	   <para>
+	   ATA_PROT_NODATA and ATA_PROT_DMA fall into this category.
+	   These types of commands don't require any software
+	   intervention once issued.  Device will raise interrupt on
+	   completion.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>ATA PIO</term>
+	   <listitem>
+	   <para>
+	   ATA_PROT_PIO is in this category.  libata currently
+	   implements PIO with polling.  ATA_NIEN bit is set to turn
+	   off interrupt and pio_task on ata_wq performs polling and
+	   IO.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>ATAPI NODATA or DMA</term>
+	   <listitem>
+	   <para>
+	   ATA_PROT_ATAPI_NODATA and ATA_PROT_ATAPI_DMA are in this
+	   category.  packet_task is used to poll BSY bit after
+	   issuing PACKET command.  Once BSY is turned off by the
+	   device, packet_task transfers CDB and hands off processing
+	   to interrupt handler.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>ATAPI PIO</term>
+	   <listitem>
+	   <para>
+	   ATA_PROT_ATAPI is in this category.  ATA_NIEN bit is set
+	   and, as in ATAPI NODATA or DMA, packet_task submits cdb.
+	   However, after submitting cdb, further processing (data
+	   transfer) is handed off to pio_task.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+	</variablelist>
+        </sect1>
+
+	<sect1><title>How commands are completed</title>
+	<para>
+	Once issued, all qc's are either completed with
+	ata_qc_complete() or time out.  For commands which are handled
+	by interrupts, ata_host_intr() invokes ata_qc_complete(), and,
+	for PIO tasks, pio_task invokes ata_qc_complete().  In error
+	cases, packet_task may also complete commands.
+	</para>
+	<para>
+	ata_qc_complete() does the following.
+	</para>
+
+	<orderedlist>
+
+	<listitem>
+	<para>
+	DMA memory is unmapped.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	ATA_QCFLAG_ACTIVE is cleared from qc->flags.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	qc->complete_fn() callback is invoked.  If the return value of
+	the callback is not zero.  Completion is short circuited and
+	ata_qc_complete() returns.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	__ata_qc_complete() is called, which does
+	   <orderedlist>
+
+	   <listitem>
+	   <para>
+	   qc->flags is cleared to zero.
+	   </para>
+	   </listitem>
+
+	   <listitem>
+	   <para>
+	   ap->active_tag and qc->tag are poisoned.
+	   </para>
+	   </listitem>
+
+	   <listitem>
+	   <para>
+	   qc->waiting is cleared &amp; completed (in that order).
+	   </para>
+	   </listitem>
+
+	   <listitem>
+	   <para>
+	   qc is deallocated by clearing appropriate bit in ap->qactive.
+	   </para>
+	   </listitem>
+
+	   </orderedlist>
+	</para>
+	</listitem>
+
+	</orderedlist>
+
+	<para>
+	So, it basically notifies upper layer and deallocates qc.  One
+	exception is short-circuit path in #3 which is used by
+	atapi_qc_complete().
+	</para>
+	<para>
+	For all non-ATAPI commands, whether it fails or not, almost
+	the same code path is taken and very little error handling
+	takes place.  A qc is completed with success status if it
+	succeeded, with failed status otherwise.
+	</para>
+	<para>
+	However, failed ATAPI commands require more handling as
+	REQUEST SENSE is needed to acquire sense data.  If an ATAPI
+	command fails, ata_qc_complete() is invoked with error status,
+	which in turn invokes atapi_qc_complete() via
+	qc->complete_fn() callback.
+	</para>
+	<para>
+	This makes atapi_qc_complete() set scmd->result to
+	SAM_STAT_CHECK_CONDITION, complete the scmd and return 1.  As
+	the sense data is empty but scmd->result is CHECK CONDITION,
+	SCSI midlayer will invoke EH for the scmd, and returning 1
+	makes ata_qc_complete() to return without deallocating the qc.
+	This leads us to ata_scsi_error() with partially completed qc.
+	</para>
+
+	</sect1>
+
+	<sect1><title>ata_scsi_error()</title>
+	<para>
+	ata_scsi_error() is the current transportt->eh_strategy_handler()
+	for libata.  As discussed above, this will be entered in two
+	cases - timeout and ATAPI error completion.  This function
+	calls low level libata driver's eng_timeout() callback, the
+	standard callback for which is ata_eng_timeout().  It checks
+	if a qc is active and calls ata_qc_timeout() on the qc if so.
+	Actual error handling occurs in ata_qc_timeout().
+	</para>
+	<para>
+	If EH is invoked for timeout, ata_qc_timeout() stops BMDMA and
+	completes the qc.  Note that as we're currently in EH, we
+	cannot call scsi_done.  As described in SCSI EH doc, a
+	recovered scmd should be either retried with
+	scsi_queue_insert() or finished with scsi_finish_command().
+	Here, we override qc->scsidone with scsi_finish_command() and
+	calls ata_qc_complete().
+	</para>
+	<para>
+	If EH is invoked due to a failed ATAPI qc, the qc here is
+	completed but not deallocated.  The purpose of this
+	half-completion is to use the qc as place holder to make EH
+	code reach this place.  This is a bit hackish, but it works.
+	</para>
+	<para>
+	Once control reaches here, the qc is deallocated by invoking
+	__ata_qc_complete() explicitly.  Then, internal qc for REQUEST
+	SENSE is issued.  Once sense data is acquired, scmd is
+	finished by directly invoking scsi_finish_command() on the
+	scmd.  Note that as we already have completed and deallocated
+	the qc which was associated with the scmd, we don't need
+	to/cannot call ata_qc_complete() again.
+	</para>
+
+	</sect1>
+
+	<sect1><title>Problems with the current EH</title>
+
+	<itemizedlist>
+
+	<listitem>
+	<para>
+	Error representation is too crude.  Currently any and all
+	error conditions are represented with ATA STATUS and ERROR
+	registers.  Errors which aren't ATA device errors are treated
+	as ATA device errors by setting ATA_ERR bit.  Better error
+	descriptor which can properly represent ATA and other
+	errors/exceptions is needed.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	When handling timeouts, no action is taken to make device
+	forget about the timed out command and ready for new commands.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	EH handling via ata_scsi_error() is not properly protected
+	from usual command processing.  On EH entrance, the device is
+	not in quiescent state.  Timed out commands may succeed or
+	fail any time.  pio_task and atapi_task may still be running.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	Too weak error recovery.  Devices / controllers causing HSM
+	mismatch errors and other errors quite often require reset to
+	return to known state.  Also, advanced error handling is
+	necessary to support features like NCQ and hotplug.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	ATA errors are directly handled in the interrupt handler and
+	PIO errors in pio_task.  This is problematic for advanced
+	error handling for the following reasons.
+	</para>
+	<para>
+	First, advanced error handling often requires context and
+	internal qc execution.
+	</para>
+	<para>
+	Second, even a simple failure (say, CRC error) needs
+	information gathering and could trigger complex error handling
+	(say, resetting &amp; reconfiguring).  Having multiple code
+	paths to gather information, enter EH and trigger actions
+	makes life painful.
+	</para>
+	<para>
+	Third, scattered EH code makes implementing low level drivers
+	difficult.  Low level drivers override libata callbacks.  If
+	EH is scattered over several places, each affected callbacks
+	should perform its part of error handling.  This can be error
+	prone and painful.
+	</para>
+	</listitem>
+
+	</itemizedlist>
+	</sect1>
+  </chapter>
+
+  <chapter id="libataExt">
+     <title>libata Library</title>
+!Edrivers/ata/libata-core.c
+  </chapter>
+
+  <chapter id="libataInt">
+     <title>libata Core Internals</title>
+!Idrivers/ata/libata-core.c
+  </chapter>
+
+  <chapter id="libataScsiInt">
+     <title>libata SCSI translation/emulation</title>
+!Edrivers/ata/libata-scsi.c
+!Idrivers/ata/libata-scsi.c
+  </chapter>
+
+  <chapter id="ataExceptions">
+     <title>ATA errors and exceptions</title>
+
+  <para>
+  This chapter tries to identify what error/exception conditions exist
+  for ATA/ATAPI devices and describe how they should be handled in
+  implementation-neutral way.
+  </para>
+
+  <para>
+  The term 'error' is used to describe conditions where either an
+  explicit error condition is reported from device or a command has
+  timed out.
+  </para>
+
+  <para>
+  The term 'exception' is either used to describe exceptional
+  conditions which are not errors (say, power or hotplug events), or
+  to describe both errors and non-error exceptional conditions.  Where
+  explicit distinction between error and exception is necessary, the
+  term 'non-error exception' is used.
+  </para>
+
+  <sect1 id="excat">
+     <title>Exception categories</title>
+     <para>
+     Exceptions are described primarily with respect to legacy
+     taskfile + bus master IDE interface.  If a controller provides
+     other better mechanism for error reporting, mapping those into
+     categories described below shouldn't be difficult.
+     </para>
+
+     <para>
+     In the following sections, two recovery actions - reset and
+     reconfiguring transport - are mentioned.  These are described
+     further in <xref linkend="exrec"/>.
+     </para>
+
+     <sect2 id="excatHSMviolation">
+        <title>HSM violation</title>
+        <para>
+        This error is indicated when STATUS value doesn't match HSM
+        requirement during issuing or execution any ATA/ATAPI command.
+        </para>
+
+	<itemizedlist>
+	<title>Examples</title>
+
+        <listitem>
+	<para>
+	ATA_STATUS doesn't contain !BSY &amp;&amp; DRDY &amp;&amp; !DRQ while trying
+	to issue a command.
+        </para>
+	</listitem>
+
+        <listitem>
+	<para>
+	!BSY &amp;&amp; !DRQ during PIO data transfer.
+        </para>
+	</listitem>
+
+        <listitem>
+	<para>
+	DRQ on command completion.
+        </para>
+	</listitem>
+
+        <listitem>
+	<para>
+	!BSY &amp;&amp; ERR after CDB transfer starts but before the
+        last byte of CDB is transferred.  ATA/ATAPI standard states
+        that &quot;The device shall not terminate the PACKET command
+        with an error before the last byte of the command packet has
+        been written&quot; in the error outputs description of PACKET
+        command and the state diagram doesn't include such
+        transitions.
+	</para>
+	</listitem>
+
+	</itemizedlist>
+
+	<para>
+	In these cases, HSM is violated and not much information
+	regarding the error can be acquired from STATUS or ERROR
+	register.  IOW, this error can be anything - driver bug,
+	faulty device, controller and/or cable.
+	</para>
+
+	<para>
+	As HSM is violated, reset is necessary to restore known state.
+	Reconfiguring transport for lower speed might be helpful too
+	as transmission errors sometimes cause this kind of errors.
+	</para>
+     </sect2>
+     
+     <sect2 id="excatDevErr">
+        <title>ATA/ATAPI device error (non-NCQ / non-CHECK CONDITION)</title>
+
+	<para>
+	These are errors detected and reported by ATA/ATAPI devices
+	indicating device problems.  For this type of errors, STATUS
+	and ERROR register values are valid and describe error
+	condition.  Note that some of ATA bus errors are detected by
+	ATA/ATAPI devices and reported using the same mechanism as
+	device errors.  Those cases are described later in this
+	section.
+	</para>
+
+	<para>
+	For ATA commands, this type of errors are indicated by !BSY
+	&amp;&amp; ERR during command execution and on completion.
+	</para>
+
+	<para>For ATAPI commands,</para>
+
+	<itemizedlist>
+
+	<listitem>
+	<para>
+	!BSY &amp;&amp; ERR &amp;&amp; ABRT right after issuing PACKET
+	indicates that PACKET command is not supported and falls in
+	this category.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	!BSY &amp;&amp; ERR(==CHK) &amp;&amp; !ABRT after the last
+	byte of CDB is transferred indicates CHECK CONDITION and
+	doesn't fall in this category.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	!BSY &amp;&amp; ERR(==CHK) &amp;&amp; ABRT after the last byte
+        of CDB is transferred *probably* indicates CHECK CONDITION and
+        doesn't fall in this category.
+	</para>
+	</listitem>
+
+	</itemizedlist>
+
+	<para>
+	Of errors detected as above, the followings are not ATA/ATAPI
+	device errors but ATA bus errors and should be handled
+	according to <xref linkend="excatATAbusErr"/>.
+	</para>
+
+	<variablelist>
+
+	   <varlistentry>
+	   <term>CRC error during data transfer</term>
+	   <listitem>
+	   <para>
+	   This is indicated by ICRC bit in the ERROR register and
+	   means that corruption occurred during data transfer.  Up to
+	   ATA/ATAPI-7, the standard specifies that this bit is only
+	   applicable to UDMA transfers but ATA/ATAPI-8 draft revision
+	   1f says that the bit may be applicable to multiword DMA and
+	   PIO.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry>
+	   <term>ABRT error during data transfer or on completion</term>
+	   <listitem>
+	   <para>
+	   Up to ATA/ATAPI-7, the standard specifies that ABRT could be
+	   set on ICRC errors and on cases where a device is not able
+	   to complete a command.  Combined with the fact that MWDMA
+	   and PIO transfer errors aren't allowed to use ICRC bit up to
+	   ATA/ATAPI-7, it seems to imply that ABRT bit alone could
+	   indicate transfer errors.
+	   </para>
+	   <para>
+	   However, ATA/ATAPI-8 draft revision 1f removes the part
+	   that ICRC errors can turn on ABRT.  So, this is kind of
+	   gray area.  Some heuristics are needed here.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	</variablelist>
+
+	<para>
+	ATA/ATAPI device errors can be further categorized as follows.
+	</para>
+
+	<variablelist>
+
+	   <varlistentry>
+	   <term>Media errors</term>
+	   <listitem>
+	   <para>
+	   This is indicated by UNC bit in the ERROR register.  ATA
+	   devices reports UNC error only after certain number of
+	   retries cannot recover the data, so there's nothing much
+	   else to do other than notifying upper layer.
+	   </para>
+	   <para>
+	   READ and WRITE commands report CHS or LBA of the first
+	   failed sector but ATA/ATAPI standard specifies that the
+	   amount of transferred data on error completion is
+	   indeterminate, so we cannot assume that sectors preceding
+	   the failed sector have been transferred and thus cannot
+	   complete those sectors successfully as SCSI does.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry>
+	   <term>Media changed / media change requested error</term>
+	   <listitem>
+	   <para>
+	   &lt;&lt;TODO: fill here&gt;&gt;
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>Address error</term>
+	   <listitem>
+	   <para>
+	   This is indicated by IDNF bit in the ERROR register.
+	   Report to upper layer.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>Other errors</term>
+	   <listitem>
+	   <para>
+	   This can be invalid command or parameter indicated by ABRT
+	   ERROR bit or some other error condition.  Note that ABRT
+	   bit can indicate a lot of things including ICRC and Address
+	   errors.  Heuristics needed.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	</variablelist>
+
+	<para>
+	Depending on commands, not all STATUS/ERROR bits are
+	applicable.  These non-applicable bits are marked with
+	&quot;na&quot; in the output descriptions but up to ATA/ATAPI-7
+	no definition of &quot;na&quot; can be found.  However,
+	ATA/ATAPI-8 draft revision 1f describes &quot;N/A&quot; as
+	follows.
+	</para>
+
+	<blockquote>
+	<variablelist>
+	   <varlistentry><term>3.2.3.3a N/A</term>
+	   <listitem>
+	   <para>
+	   A keyword the indicates a field has no defined value in
+	   this standard and should not be checked by the host or
+	   device. N/A fields should be cleared to zero.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+	</variablelist>
+	</blockquote>
+
+	<para>
+	So, it seems reasonable to assume that &quot;na&quot; bits are
+	cleared to zero by devices and thus need no explicit masking.
+	</para>
+
+     </sect2>
+
+     <sect2 id="excatATAPIcc">
+        <title>ATAPI device CHECK CONDITION</title>
+
+	<para>
+	ATAPI device CHECK CONDITION error is indicated by set CHK bit
+	(ERR bit) in the STATUS register after the last byte of CDB is
+	transferred for a PACKET command.  For this kind of errors,
+	sense data should be acquired to gather information regarding
+	the errors.  REQUEST SENSE packet command should be used to
+	acquire sense data.
+	</para>
+
+	<para>
+	Once sense data is acquired, this type of errors can be
+	handled similarly to other SCSI errors.  Note that sense data
+	may indicate ATA bus error (e.g. Sense Key 04h HARDWARE ERROR
+	&amp;&amp; ASC/ASCQ 47h/00h SCSI PARITY ERROR).  In such
+	cases, the error should be considered as an ATA bus error and
+	handled according to <xref linkend="excatATAbusErr"/>.
+	</para>
+
+     </sect2>
+
+     <sect2 id="excatNCQerr">
+        <title>ATA device error (NCQ)</title>
+
+	<para>
+	NCQ command error is indicated by cleared BSY and set ERR bit
+	during NCQ command phase (one or more NCQ commands
+	outstanding).  Although STATUS and ERROR registers will
+	contain valid values describing the error, READ LOG EXT is
+	required to clear the error condition, determine which command
+	has failed and acquire more information.
+	</para>
+
+	<para>
+	READ LOG EXT Log Page 10h reports which tag has failed and
+	taskfile register values describing the error.  With this
+	information the failed command can be handled as a normal ATA
+	command error as in <xref linkend="excatDevErr"/> and all
+	other in-flight commands must be retried.  Note that this
+	retry should not be counted - it's likely that commands
+	retried this way would have completed normally if it were not
+	for the failed command.
+	</para>
+
+	<para>
+	Note that ATA bus errors can be reported as ATA device NCQ
+	errors.  This should be handled as described in <xref
+	linkend="excatATAbusErr"/>.
+	</para>
+
+	<para>
+	If READ LOG EXT Log Page 10h fails or reports NQ, we're
+	thoroughly screwed.  This condition should be treated
+	according to <xref linkend="excatHSMviolation"/>.
+	</para>
+
+     </sect2>
+
+     <sect2 id="excatATAbusErr">
+        <title>ATA bus error</title>
+
+	<para>
+	ATA bus error means that data corruption occurred during
+	transmission over ATA bus (SATA or PATA).  This type of errors
+	can be indicated by
+	</para>
+
+	<itemizedlist>
+
+	<listitem>
+	<para>
+	ICRC or ABRT error as described in <xref linkend="excatDevErr"/>.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	Controller-specific error completion with error information
+	indicating transmission error.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	On some controllers, command timeout.  In this case, there may
+	be a mechanism to determine that the timeout is due to
+	transmission error.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	Unknown/random errors, timeouts and all sorts of weirdities.
+	</para>
+	</listitem>
+
+	</itemizedlist>
+
+	<para>
+	As described above, transmission errors can cause wide variety
+	of symptoms ranging from device ICRC error to random device
+	lockup, and, for many cases, there is no way to tell if an
+	error condition is due to transmission error or not;
+	therefore, it's necessary to employ some kind of heuristic
+	when dealing with errors and timeouts.  For example,
+	encountering repetitive ABRT errors for known supported
+	command is likely to indicate ATA bus error.
+	</para>
+
+	<para>
+	Once it's determined that ATA bus errors have possibly
+	occurred, lowering ATA bus transmission speed is one of
+	actions which may alleviate the problem.  See <xref
+	linkend="exrecReconf"/> for more information.
+	</para>
+
+     </sect2>
+
+     <sect2 id="excatPCIbusErr">
+        <title>PCI bus error</title>
+
+	<para>
+	Data corruption or other failures during transmission over PCI
+	(or other system bus).  For standard BMDMA, this is indicated
+	by Error bit in the BMDMA Status register.  This type of
+	errors must be logged as it indicates something is very wrong
+	with the system.  Resetting host controller is recommended.
+	</para>
+
+     </sect2>
+
+     <sect2 id="excatLateCompletion">
+        <title>Late completion</title>
+
+	<para>
+	This occurs when timeout occurs and the timeout handler finds
+	out that the timed out command has completed successfully or
+	with error.  This is usually caused by lost interrupts.  This
+	type of errors must be logged.  Resetting host controller is
+	recommended.
+	</para>
+
+     </sect2>
+
+     <sect2 id="excatUnknown">
+        <title>Unknown error (timeout)</title>
+
+	<para>
+	This is when timeout occurs and the command is still
+	processing or the host and device are in unknown state.  When
+	this occurs, HSM could be in any valid or invalid state.  To
+	bring the device to known state and make it forget about the
+	timed out command, resetting is necessary.  The timed out
+	command may be retried.
+	</para>
+
+	<para>
+	Timeouts can also be caused by transmission errors.  Refer to
+	<xref linkend="excatATAbusErr"/> for more details.
+	</para>
+
+     </sect2>
+
+     <sect2 id="excatHoplugPM">
+        <title>Hotplug and power management exceptions</title>
+
+	<para>
+	&lt;&lt;TODO: fill here&gt;&gt;
+	</para>
+
+     </sect2>
+
+  </sect1>
+
+  <sect1 id="exrec">
+     <title>EH recovery actions</title>
+
+     <para>
+     This section discusses several important recovery actions.
+     </para>
+
+     <sect2 id="exrecClr">
+        <title>Clearing error condition</title>
+
+	<para>
+	Many controllers require its error registers to be cleared by
+	error handler.  Different controllers may have different
+	requirements.
+	</para>
+
+	<para>
+	For SATA, it's strongly recommended to clear at least SError
+	register during error handling.
+	</para>
+     </sect2>
+
+     <sect2 id="exrecRst">
+        <title>Reset</title>
+
+	<para>
+	During EH, resetting is necessary in the following cases.
+	</para>
+
+	<itemizedlist>
+
+	<listitem>
+	<para>
+	HSM is in unknown or invalid state
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	HBA is in unknown or invalid state
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	EH needs to make HBA/device forget about in-flight commands
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	HBA/device behaves weirdly
+	</para>
+	</listitem>
+
+	</itemizedlist>
+
+	<para>
+	Resetting during EH might be a good idea regardless of error
+	condition to improve EH robustness.  Whether to reset both or
+	either one of HBA and device depends on situation but the
+	following scheme is recommended.
+	</para>
+
+	<itemizedlist>
+
+	<listitem>
+	<para>
+	When it's known that HBA is in ready state but ATA/ATAPI
+	device is in unknown state, reset only device.
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	If HBA is in unknown state, reset both HBA and device.
+	</para>
+	</listitem>
+
+	</itemizedlist>
+
+	<para>
+	HBA resetting is implementation specific.  For a controller
+	complying to taskfile/BMDMA PCI IDE, stopping active DMA
+	transaction may be sufficient iff BMDMA state is the only HBA
+	context.  But even mostly taskfile/BMDMA PCI IDE complying
+	controllers may have implementation specific requirements and
+	mechanism to reset themselves.  This must be addressed by
+	specific drivers.
+	</para>
+
+	<para>
+	OTOH, ATA/ATAPI standard describes in detail ways to reset
+	ATA/ATAPI devices.
+	</para>
+
+	<variablelist>
+
+	   <varlistentry><term>PATA hardware reset</term>
+	   <listitem>
+	   <para>
+	   This is hardware initiated device reset signalled with
+	   asserted PATA RESET- signal.  There is no standard way to
+	   initiate hardware reset from software although some
+	   hardware provides registers that allow driver to directly
+	   tweak the RESET- signal.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>Software reset</term>
+	   <listitem>
+	   <para>
+	   This is achieved by turning CONTROL SRST bit on for at
+	   least 5us.  Both PATA and SATA support it but, in case of
+	   SATA, this may require controller-specific support as the
+	   second Register FIS to clear SRST should be transmitted
+	   while BSY bit is still set.  Note that on PATA, this resets
+	   both master and slave devices on a channel.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>EXECUTE DEVICE DIAGNOSTIC command</term>
+	   <listitem>
+	   <para>
+	   Although ATA/ATAPI standard doesn't describe exactly, EDD
+	   implies some level of resetting, possibly similar level
+	   with software reset.  Host-side EDD protocol can be handled
+	   with normal command processing and most SATA controllers
+	   should be able to handle EDD's just like other commands.
+	   As in software reset, EDD affects both devices on a PATA
+	   bus.
+	   </para>
+	   <para>
+	   Although EDD does reset devices, this doesn't suit error
+	   handling as EDD cannot be issued while BSY is set and it's
+	   unclear how it will act when device is in unknown/weird
+	   state.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>ATAPI DEVICE RESET command</term>
+	   <listitem>
+	   <para>
+	   This is very similar to software reset except that reset
+	   can be restricted to the selected device without affecting
+	   the other device sharing the cable.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	   <varlistentry><term>SATA phy reset</term>
+	   <listitem>
+	   <para>
+	   This is the preferred way of resetting a SATA device.  In
+	   effect, it's identical to PATA hardware reset.  Note that
+	   this can be done with the standard SCR Control register.
+	   As such, it's usually easier to implement than software
+	   reset.
+	   </para>
+	   </listitem>
+	   </varlistentry>
+
+	</variablelist>
+
+	<para>
+	One more thing to consider when resetting devices is that
+	resetting clears certain configuration parameters and they
+	need to be set to their previous or newly adjusted values
+	after reset.
+	</para>
+
+	<para>
+	Parameters affected are.
+	</para>
+
+	<itemizedlist>
+
+	<listitem>
+	<para>
+	CHS set up with INITIALIZE DEVICE PARAMETERS (seldom used)
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	Parameters set with SET FEATURES including transfer mode setting
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	Block count set with SET MULTIPLE MODE
+	</para>
+	</listitem>
+
+	<listitem>
+	<para>
+	Other parameters (SET MAX, MEDIA LOCK...)
+	</para>
+	</listitem>
+
+	</itemizedlist>
+
+	<para>
+	ATA/ATAPI standard specifies that some parameters must be
+	maintained across hardware or software reset, but doesn't
+	strictly specify all of them.  Always reconfiguring needed
+	parameters after reset is required for robustness.  Note that
+	this also applies when resuming from deep sleep (power-off).
+	</para>
+
+	<para>
+	Also, ATA/ATAPI standard requires that IDENTIFY DEVICE /
+	IDENTIFY PACKET DEVICE is issued after any configuration
+	parameter is updated or a hardware reset and the result used
+	for further operation.  OS driver is required to implement
+	revalidation mechanism to support this.
+	</para>
+
+     </sect2>
+
+     <sect2 id="exrecReconf">
+        <title>Reconfigure transport</title>
+
+	<para>
+	For both PATA and SATA, a lot of corners are cut for cheap
+	connectors, cables or controllers and it's quite common to see
+	high transmission error rate.  This can be mitigated by
+	lowering transmission speed.
+	</para>
+
+	<para>
+	The following is a possible scheme Jeff Garzik suggested.
+	</para>
+
+	<blockquote>
+	<para>
+	If more than $N (3?) transmission errors happen in 15 minutes,
+	</para>	
+	<itemizedlist>
+	<listitem>
+	<para>
+	if SATA, decrease SATA PHY speed.  if speed cannot be decreased,
+	</para>
+	</listitem>
+	<listitem>
+	<para>
+	decrease UDMA xfer speed.  if at UDMA0, switch to PIO4,
+	</para>
+	</listitem>
+	<listitem>
+	<para>
+	decrease PIO xfer speed.  if at PIO3, complain, but continue
+	</para>
+	</listitem>
+	</itemizedlist>
+	</blockquote>
+
+     </sect2>
+
+  </sect1>
+
+  </chapter>
+
+  <chapter id="PiixInt">
+     <title>ata_piix Internals</title>
+!Idrivers/ata/ata_piix.c
+  </chapter>
+
+  <chapter id="SILInt">
+     <title>sata_sil Internals</title>
+!Idrivers/ata/sata_sil.c
+  </chapter>
+
+  <chapter id="libataThanks">
+     <title>Thanks</title>
+  <para>
+  The bulk of the ATA knowledge comes thanks to long conversations with
+  Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA
+  and SCSI specifications.
+  </para>
+  <para>
+  Thanks to Alan Cox for pointing out similarities 
+  between SATA and SCSI, and in general for motivation to hack on
+  libata.
+  </para>
+  <para>
+  libata's device detection
+  method, ata_pio_devchk, and in general all the early probing was
+  based on extensive study of Hale Landis's probe/reset code in his
+  ATADRVR driver (www.ata-atapi.com).
+  </para>
+  </chapter>
+
+</book>