On Sat, 27 Jan 2007, Soeren Sonnenburg wrote:
> I realized that any setting to /sys/module/usbhid/parameters/pb_fnmode
> is just ignored until the machine does a suspend-resume cycle.
Hi Soeren,
I would probably not call this a regression, as this has been always
there, as far as I can see.
> I've added a printk in drivers/usb/input/hid-core.c (which is the only
> place where hid->pb_fnmode is set) and indeed only on module load ( in
> my case usbhid is compiled into the kernel - so on kernel boot) any
> change to hid>pb_fnmode is done. Adding a printk to hidinput_pb_event()
> in drivers/hid/hid-input.c says the same: hid->pb_fnmode cannot be
> changed on the fly anymore... HOWEVER: If I s2ram the machine
> hid->pb_fnmode is initialized with the value I put into
> /sys/module/usbhid/parameters/pb_fnmode . As I have no idea how/whether
> sysfs works/is possible I now hope someone more knowledgable than me can
> resolve this issue!
Changing module parameter values through sysfs is not a very nice idea,
because the change of the value is indeed silent - the driver is not
notified in any way, that the value has changed. So the driver should take
care of it by itself, which is not a nice thing.
The fact that during suspend/resume cycle it works is caused by the fact
that all the hid devices are reinitialized, and therefore the
hid->pb_fnmode is reassigned a new value, which has eventually been
changed through sysfs.
I would rather be inclined to just make the
/sys/module/usbhid/parameters/pb_fnmode read-only (which is what most of
the drivers do anyway), to avoid this kind of confusion.
Do you have really any strong use-case, when setting the parameter during
runtime would be much more useful than just do it during modprobe or
rmmod/modprobe cycle?
Thanks,
--
Jiri Kosina
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