On 13.01.2012 12:42, Hans Verkuil wrote: > Hi! Hi! Adding Jiri Kosina, the HID maintainer. > I've made a video4linux driver for the USB Keene FM Transmitter. See: > > http://www.amazon.co.uk/Keene-Electronics-USB-FM-Transmitter/dp/B003GCHPDY/ref=sr_1_1?ie=UTF8&qid=1326450476&sr=8-1 > > The driver code is here: > > http://git.linuxtv.org/hverkuil/media_tree.git/shortlog/refs/heads/keene > > Unfortunately this device has exactly the same USB ID as the Logitech AudioHub > USB speaker (http://www.logitech.com/en-us/439/3503). > > The AudioHub has HID support for volume keys, but the FM transmitter needs > a custom V4L2 driver instead. > > I've attached the full lsusb -v output of both devices, but this is the diff of > the two: > > $ diff keene.txt audiohub.txt -u [...] > @@ -152,7 +151,7 @@ > bCountryCode 0 Not supported > bNumDescriptors 1 > bDescriptorType 34 Report > - wDescriptorLength 22 > + wDescriptorLength 31 > Report Descriptors: > ** UNAVAILABLE ** > Endpoint Descriptor: > > As you can see, the differences are very small. The HID Report descriptors could be interesting as they differ. You can look at them in: /sys/kernel/debug/hid/*/rdesc I guess one option would be to make this a "regular" HID driver like those in drivers/hid/hid-*.c (and just set the v4l things up if the descriptor is as expected, otherwise let standard HID-input handle them), but there is the issue of where to place the driver, then, as it can't be both in drivers/hid and drivers/media... Probably the easy way out is to simply add the device into drivers/hid/hid-core.c:hid_ignore(), by checking e.g. vendor+product+name, and hope all "B-LINK USB Audio" devices are FM transmitters (the name suggests that may not necessarily be the case, though). Report descriptor contents are not available at hid_ignore() point yet. > In my git tree I worked around it by adding the USB ID to the ignore list > if the Keene driver is enabled, and ensuring that the Keene driver is > disabled by default. > > But is there a better method to do this? At least the iProduct strings are > different, is that something that can be tested in hid-core.c? > > Regards, > > Hans -- Anssi Hannula -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
