diff options
author | Yunhong Jiang <yunhong.jiang@intel.com> | 2015-08-04 12:17:53 -0700 |
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committer | Yunhong Jiang <yunhong.jiang@intel.com> | 2015-08-04 15:44:42 -0700 |
commit | 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch) | |
tree | 1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/Documentation/misc-devices/mei/mei-client-bus.txt | |
parent | 98260f3884f4a202f9ca5eabed40b1354c489b29 (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>
Diffstat (limited to 'kernel/Documentation/misc-devices/mei/mei-client-bus.txt')
-rw-r--r-- | kernel/Documentation/misc-devices/mei/mei-client-bus.txt | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/kernel/Documentation/misc-devices/mei/mei-client-bus.txt b/kernel/Documentation/misc-devices/mei/mei-client-bus.txt new file mode 100644 index 000000000..743be4ec8 --- /dev/null +++ b/kernel/Documentation/misc-devices/mei/mei-client-bus.txt @@ -0,0 +1,141 @@ +Intel(R) Management Engine (ME) Client bus API +============================================== + + +Rationale +========= + +MEI misc character device is useful for dedicated applications to send and receive +data to the many FW appliance found in Intel's ME from the user space. +However for some of the ME functionalities it make sense to leverage existing software +stack and expose them through existing kernel subsystems. + +In order to plug seamlessly into the kernel device driver model we add kernel virtual +bus abstraction on top of the MEI driver. This allows implementing linux kernel drivers +for the various MEI features as a stand alone entities found in their respective subsystem. +Existing device drivers can even potentially be re-used by adding an MEI CL bus layer to +the existing code. + + +MEI CL bus API +============== + +A driver implementation for an MEI Client is very similar to existing bus +based device drivers. The driver registers itself as an MEI CL bus driver through +the mei_cl_driver structure: + +struct mei_cl_driver { + struct device_driver driver; + const char *name; + + const struct mei_cl_device_id *id_table; + + int (*probe)(struct mei_cl_device *dev, const struct mei_cl_id *id); + int (*remove)(struct mei_cl_device *dev); +}; + +struct mei_cl_id { + char name[MEI_NAME_SIZE]; + kernel_ulong_t driver_info; +}; + +The mei_cl_id structure allows the driver to bind itself against a device name. + +To actually register a driver on the ME Client bus one must call the mei_cl_add_driver() +API. This is typically called at module init time. + +Once registered on the ME Client bus, a driver will typically try to do some I/O on +this bus and this should be done through the mei_cl_send() and mei_cl_recv() +routines. The latter is synchronous (blocks and sleeps until data shows up). +In order for drivers to be notified of pending events waiting for them (e.g. +an Rx event) they can register an event handler through the +mei_cl_register_event_cb() routine. Currently only the MEI_EVENT_RX event +will trigger an event handler call and the driver implementation is supposed +to call mei_recv() from the event handler in order to fetch the pending +received buffers. + + +Example +======= + +As a theoretical example let's pretend the ME comes with a "contact" NFC IP. +The driver init and exit routines for this device would look like: + +#define CONTACT_DRIVER_NAME "contact" + +static struct mei_cl_device_id contact_mei_cl_tbl[] = { + { CONTACT_DRIVER_NAME, }, + + /* required last entry */ + { } +}; +MODULE_DEVICE_TABLE(mei_cl, contact_mei_cl_tbl); + +static struct mei_cl_driver contact_driver = { + .id_table = contact_mei_tbl, + .name = CONTACT_DRIVER_NAME, + + .probe = contact_probe, + .remove = contact_remove, +}; + +static int contact_init(void) +{ + int r; + + r = mei_cl_driver_register(&contact_driver); + if (r) { + pr_err(CONTACT_DRIVER_NAME ": driver registration failed\n"); + return r; + } + + return 0; +} + +static void __exit contact_exit(void) +{ + mei_cl_driver_unregister(&contact_driver); +} + +module_init(contact_init); +module_exit(contact_exit); + +And the driver's simplified probe routine would look like that: + +int contact_probe(struct mei_cl_device *dev, struct mei_cl_device_id *id) +{ + struct contact_driver *contact; + + [...] + mei_cl_enable_device(dev); + + mei_cl_register_event_cb(dev, contact_event_cb, contact); + + return 0; +} + +In the probe routine the driver first enable the MEI device and then registers +an ME bus event handler which is as close as it can get to registering a +threaded IRQ handler. +The handler implementation will typically call some I/O routine depending on +the pending events: + +#define MAX_NFC_PAYLOAD 128 + +static void contact_event_cb(struct mei_cl_device *dev, u32 events, + void *context) +{ + struct contact_driver *contact = context; + + if (events & BIT(MEI_EVENT_RX)) { + u8 payload[MAX_NFC_PAYLOAD]; + int payload_size; + + payload_size = mei_recv(dev, payload, MAX_NFC_PAYLOAD); + if (payload_size <= 0) + return; + + /* Hook to the NFC subsystem */ + nfc_hci_recv_frame(contact->hdev, payload, payload_size); + } +} |