On Monday 08 October 2007, Jörg Hermsdorf wrote:
> >> Does the dynctl api allows this additional functionality to be
>
>  exported via
>
> >> the sysfs filesystem, too? Or would this require an additional
>
>  sub-module
>
> >> e.g. uvcvideo-logitech.ko which exports this (and only this)
>
>  additional
>
> >> functionality via sysfs?
> >
> > No sysfs exports exists yet. What exactly do you want to export ? V4L2
> > controls ? UVC controls ? How do you handle permissions on those ?
>
> For instance, I would like to be able to easily control the LED one day
> e.g. via:
>
> # echo "blinking" > /sys/module/uvcvideo/parameters/status_led
> # echo "auto" > /sys/module/uvcvideo/parameters/status_led
> # echo "on" > /sys/module/uvcvideo/parameters/status_led
> # echo "off" > /sys/module/uvcvideo/parameters/status_led
>
>
>
> Permissions should be set via udev rules, e.g. like this:
>
> KERNEL=="uvcvideo",                GROUP="video", MODE="0664"
>
> So every user which is in the group 'video' could write/set the LED,
> if it was exported via sysfs. And if you don't want that, you could
> change the GROUP or MODE values to your needs.

Do udev rules apply to sysfs as well ?

> I must admit, I don't know much about ioctls (yet). But it seems like,
> if I would like to control the LED at the moment, I would need to write
> my own code, correct? There's no way to access ioctls directly from
> within a shell? So having sysfs hooks for certain settings and controls
> would be very nice.

An alternative for now would be to use a userspace tool to get and set the 
controls (something similar to v4lctl). It would work for all V4L2 devices 
witgout requiring sysfs support in all drivers.

Best regards,

Laurent Pinchart
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