Hi,
On 02/27/2010 04:35 PM, Németh Márton wrote:
Hi,
Jean-Francois Moine wrote:
On Sat, 27 Feb 2010 08:53:16 +0100
Hans de Goede<hdegoede@xxxxxxxxxx> wrote:
This is true for a lot of cameras, so if we are going to add a way to
support control of the LED separate of the streaming state, we
should do that at the gspca_main level, and let sub drivers which
support this export a set_led callback function.
I must say I personally don't see much of a use case for this feature,
but I believe JF Moine does, so I'll leave further comments and
review of this to JF. I do believe it is important that if we go this
way we do so add the gspca_main level.
Hi,
I don't like this mechanism to switch on or off the webcam LEDs. Here
are some arguments (some of them were sent last year to the list):
I could accept both the V4L2 control solution or the LED subclass solution
for handling the camera LED. I miss a little the positive side of using
the LED subclass from the list, so I try take the role of that side and
add them.
I have to side with JF here, I see very little use in the led class interface
for webcams. Another important reason to choose for a simple v4l2 menu control
solution here is consistency certain logitech uvc cameras already offer Led control
through a vendor extension control unit, which (when using uvcdynctrl to enable
vendor extension control units), currently shows up as a v4l2 control.
So for consistency with existing practices a v4l2 control seems better suited.
Also I must say that the led class seems overkill.
I would like to note that even if we go the v4l2 control way it still makes sense
to handle this in gspca_main, rather then implementing it separately in every
sub driver.
1) End users.
Many Linux users don't know the kernel internals, nor which of the too
many applications they should use to make their devices work.
Actually, there are a few X11 programs in common Linux distros which can
handle the webcam parameters: I just know about vlc and v4l2ucp, and
they don't even handle the VIDIOC_G_JPEGCOMP and VIDIOC_S_JPEGCOMP
ioctls which are part of the v4l2 API.
The LED interface uses the /sys file system. Will the webcam programs
offer access to this interface? I don't believe it. So, the users will
have to search how they can switch on or off the LEDs of their webcams,
and then, when found, they should start a X terminal and run a command
to do the job!
The programs like v4l2ucp can be extended to handle the /sys/class/leds
interface. This is work but the user will not recognise the difference
as long as the GUI supports it.
Erm, no currently almost no v4l programs uses v4l2 controls properly, and
I certainly see none supporting the led sysfs interface. I say this as
someone who has done actual development on v4l2ucp, and who is currnetly
involved in writing a GTK v4l2 control panel application.
Regards,
Hans
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