firmware loader: introduce module parameter to customize(v4) fw search path

This patch introduces one module parameter of 'path' in firmware_class
to support customizing firmware image search path, so that people can
use its own firmware path if the default built-in paths can't meet their
demand[1], and the typical usage is passing the below from kernel command
parameter when 'firmware_class' is built in kernel:

	firmware_class.path=$CUSTOMIZED_PATH

[1], https://lkml.org/lkml/2012/10/11/337

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>

1 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/firmware_class/README b/Documentation/firmware_class/README
index 815b711bcd85..e9fce78c4137 100644
--- a/Documentation/firmware_class/README
+++ b/Documentation/firmware_class/README
@@ -22,12 +22,17 @@
         - calls request_firmware(&fw_entry, $FIRMWARE, device)
         - kernel searchs the fimware image with name $FIRMWARE directly
         in the below search path of root filesystem:
+                User customized search path by module parameter 'path'[1]
                 "/lib/firmware/updates/" UTS_RELEASE,
                 "/lib/firmware/updates",
                 "/lib/firmware/" UTS_RELEASE,
                 "/lib/firmware"
         - If found, goto 7), else goto 2)
 
+        [1], the 'path' is a string parameter which length should be less
+        than 256, user should pass 'firmware_class.path=$CUSTOMIZED_PATH'
+        if firmware_class is built in kernel(the general situation)
+
  2), userspace:
         - /sys/class/firmware/xxx/{loading,data} appear.
         - hotplug gets called with a firmware identifier in $FIRMWARE