Hi,
On 01/12/2010 09:01 PM, Greg KH wrote:
Fixing userspace bugs with kernel driver changes seems a bit harsh :)
Oh I completely agree, and I also agree that apps which looses their
/dev/video device because of unplug should handle that properly, still
the stealing of the device from the webcam app by libgphoto apps is
unwanted behavior in my book, and that is what I'm trying to fix.
Then fix libgphoto please. I don't see a kernel issue here yet.
Well libgphoto2 politely asks the kernel, can you please release usb device
foo for userspace use ? I'm asking for drivers to have the possibility to
say: No sorry, the device is in use.
This does not seem something strange to me. This can be hacked around
in libgphoto by:
1) Adding code to match the usb device to a /dev/video
2) If it matches a /dev/video, open that (this will work multiple opens
are allowed)
3) Try to start a stream (yes because we really want libgphoto2 to
have to start the webcam)
4) If 3) fails with ebusy, an other app is already streaming, don't ask
the kernel to release the device.
5) If 3) does not fail, close the device and continue
That would be a gross hack, but that would be the way to "fix" libgphoto2 .
Or we could have the please release the device call return -EBUSY, which
almost every other single syscall in the kernel will do when a single use
device is already in use by another application.
Regards,
Hans
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