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firmware loader: document kernel direct loading

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

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ming Lei
2012-10-24 10:49:33 +08:00
committed by Greg Kroah-Hartman
parent 66081a7251
commit 10bd4c7572
1 changed files with 16 additions and 8 deletions
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24
Documentation/firmware_class/README
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@@ -18,32 +18,40 @@
High level behavior (mixed): High level behavior (mixed):
============================ ============================
kernel(driver): calls request_firmware(&fw_entry, $FIRMWARE, device) 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)
userspace: 2), userspace:
- /sys/class/firmware/xxx/{loading,data} appear. - /sys/class/firmware/xxx/{loading,data} appear.
- hotplug gets called with a firmware identifier in $FIRMWARE - hotplug gets called with a firmware identifier in $FIRMWARE
and the usual hotplug environment. and the usual hotplug environment.
- hotplug: echo 1 > /sys/class/firmware/xxx/loading - 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 > \ - hotplug: cat appropriate_firmware_image > \
/sys/class/firmware/xxx/data /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. comes in.
userspace: 6), userspace:
- hotplug: echo 0 > /sys/class/firmware/xxx/loading - 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 image in fw_entry->{data,size}. If something went wrong
request_firmware() returns non-zero and fw_entry is set to request_firmware() returns non-zero and fw_entry is set to
NULL. 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. the firmware image and any related resource.
High level behavior (driver code): High level behavior (driver code):