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Commit 10bd4c75 authored by Ming Lei's avatar Ming Lei Committed by Greg Kroah-Hartman
Browse files

firmware loader: document kernel direct loading 



This patch adds description on recently introduced direct firmware
loading by Linus.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 66081a72

Documentation/firmware_class/README

+17 −9
Original line number Diff line number Diff line
@@ -18,32 +18,40 @@ 
 High level behavior (mixed):

 ============================



 kernel(driver): calls request_firmware(&fw_entry, $FIRMWARE, device)



 userspace:

 1), kernel(driver):

	- calls request_firmware(&fw_entry, $FIRMWARE, device)

	- kernel searchs the fimware image with name $FIRMWARE directly

	in the below search path of root filesystem:

		"/lib/firmware/updates/" UTS_RELEASE,

		"/lib/firmware/updates",

		"/lib/firmware/" UTS_RELEASE,

		"/lib/firmware"

	- If found, goto 7), else goto 2)



 2), userspace:

 	- /sys/class/firmware/xxx/{loading,data} appear.

	- hotplug gets called with a firmware identifier in $FIRMWARE

	  and the usual hotplug environment.

		- hotplug: echo 1 > /sys/class/firmware/xxx/loading



 kernel: Discard any previous partial load.

 3), kernel: Discard any previous partial load.



 userspace:

 4), userspace:

		- hotplug: cat appropriate_firmware_image > \

					/sys/class/firmware/xxx/data



 kernel: grows a buffer in PAGE_SIZE increments to hold the image as it

 5), kernel: grows a buffer in PAGE_SIZE increments to hold the image as it

	 comes in.



 userspace:

 6), userspace:

		- hotplug: echo 0 > /sys/class/firmware/xxx/loading



 kernel: request_firmware() returns and the driver has the firmware

 7), kernel: request_firmware() returns and the driver has the firmware

	 image in fw_entry->{data,size}. If something went wrong

	 request_firmware() returns non-zero and fw_entry is set to

	 NULL.



 kernel(driver): Driver code calls release_firmware(fw_entry) releasing

 8), kernel(driver): Driver code calls release_firmware(fw_entry) releasing

		 the firmware image and any related resource.



 High level behavior (driver code):