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authorYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 12:17:53 -0700
committerYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 15:44:42 -0700
commit9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch)
tree1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/Documentation/scsi/megaraid.txt
parent98260f3884f4a202f9ca5eabed40b1354c489b29 (diff)
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>
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+ Notes on Management Module
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Overview:
+--------
+
+Different classes of controllers from LSI Logic accept and respond to the
+user applications in a similar way. They understand the same firmware control
+commands. Furthermore, the applications also can treat different classes of
+the controllers uniformly. Hence it is logical to have a single module that
+interfaces with the applications on one side and all the low level drivers
+on the other.
+
+The advantages, though obvious, are listed for completeness:
+
+ i. Avoid duplicate code from the low level drivers.
+ ii. Unburden the low level drivers from having to export the
+ character node device and related handling.
+ iii. Implement any policy mechanisms in one place.
+ iv. Applications have to interface with only module instead of
+ multiple low level drivers.
+
+Currently this module (called Common Management Module) is used only to issue
+ioctl commands. But this module is envisioned to handle all user space level
+interactions. So any 'proc', 'sysfs' implementations will be localized in this
+common module.
+
+Credits:
+-------
+
+"Shared code in a third module, a "library module", is an acceptable
+solution. modprobe automatically loads dependent modules, so users
+running "modprobe driver1" or "modprobe driver2" would automatically
+load the shared library module."
+
+ - Jeff Garzik (jgarzik@pobox.com), 02.25.2004 LKML
+
+"As Jeff hinted, if your userspace<->driver API is consistent between
+your new MPT-based RAID controllers and your existing megaraid driver,
+then perhaps you need a single small helper module (lsiioctl or some
+better name), loaded by both mptraid and megaraid automatically, which
+handles registering the /dev/megaraid node dynamically. In this case,
+both mptraid and megaraid would register with lsiioctl for each
+adapter discovered, and lsiioctl would essentially be a switch,
+redirecting userspace tool ioctls to the appropriate driver."
+
+ - Matt Domsch, (Matt_Domsch@dell.com), 02.25.2004 LKML
+
+Design:
+------
+
+The Common Management Module is implemented in megaraid_mm.[ch] files. This
+module acts as a registry for low level hba drivers. The low level drivers
+(currently only megaraid) register each controller with the common module.
+
+The applications interface with the common module via the character device
+node exported by the module.
+
+The lower level drivers now understand only a new improved ioctl packet called
+uioc_t. The management module converts the older ioctl packets from the older
+applications into uioc_t. After driver handles the uioc_t, the common module
+will convert that back into the old format before returning to applications.
+
+As new applications evolve and replace the old ones, the old packet format
+will be retired.
+
+Common module dedicates one uioc_t packet to each controller registered. This
+can easily be more than one. But since megaraid is the only low level driver
+today, and it can handle only one ioctl, there is no reason to have more. But
+as new controller classes get added, this will be tuned appropriately.