> Hi Hans,
>
> On Wednesday 25 March 2009 11:18:31 Hans de Goede wrote:
>> <take 2 this time to the new list, hoping it gets some more attention>
>>
>> Hi,
>>
>> Today it came to my attention (through a libv4l bugreport) that
>> the uvc driver and the gspca driver handle the setting of
>> the v4l parent for usb webcams differently.
>>
>> The probe function for an usb driver gets passed in a
>> "struct usb_interface *intf" parameter.
>>
>> uvc sets parent to:
>>
>> vdev->parent = &intf->dev;
>>
>> gspca uses:
>> struct usb_device *dev = interface_to_usbdev(intf);
>> vdev.parent = &dev->dev;
>>
>> Looking at what for example the usb mass-storage driver
>> does (with my multi function printer/scanner with cardreader),
>> which matches UVC, and thinking about how this is supposed to
>> work with multifunction devices in general, I believe the uvc
>> driver behaviour is correct, but before writing a patch for
>> gspca, I thought it would be good to first discuss this on the
>> list.
>>
>> So what do you think ?
>
> I obviously agree with you :-)
>
> USB class drivers bind to interfaces instead of devices to support
> composite
> (multifunction) devices. While drivers for vendor-specific USB devices can
> bind to the device, in which case the parent could be a USB device, we
> need to
> have some consistency in the sysfs symlinks. Using a USB interface as the
> video device parent regardless of the device type makes sense.
If the parent should indeed become the usb_interface, then we should make
all v4l usb drivers consistent. And update v4l2-framework.txt. I've
noticed before that it seems to be random what is used as the parent. I'm
no USB expert, so I'm relying on your input.
Regards,
Hans
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG
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