On Feb 25, 2011, at 3:26 AM, Carl Lindqvist wrote:
Hello Alan!
My name is Carl, and I am working on a project which uses a purpose
built USB-device from X-Keys. To change the states of the LEDs on
the device I write to it using hidraw. I noticed that you are the
one who has been changing the way hidraw behaves in the kernel, and
I was wondering if you had the time to answer a few questions.
Writing to the hidraw device works like a charm using ubuntu 10.10
with the 2.6.35-23 kernel. However, my system uses hardware that
doesn't play very nice with anything above 2.6.34 at the moment.
When using this older kernel, I can't manage to write to the hidraw
device. Nothing I try works. I noticed that there were changed to
hidraw, and you seem to be the expert.
I'm far from the expert :)
I simply use the "write(fd, buf, length)" to send the data, and it
works great in 2.6.35, but just produces a write failed message on
older kernels. Do you know if it is possible to write to the device
in some other way? Or do I need the newer kernel for that?
I am sorry to botheryou directly, but I figured you were the best
person to ask.
Typically this type of thing should go to the linux-input mailing
list, I cc'd them.
The HID support from HIDRAW was kind of basic in older kernels and
didn't support all the behaviors in the HID spec. For example, on
older kernels output reports would only be sent on the control
endpoint, but in newer kernels, the behavior is more compliant with
the USB HID spec, sending data on an interrupt OUT endpoint if one is
available.[1]
This breaks devices which expect the Output reports to come on the OUT
endpoint (instead of the control endpoint).
Try applying [1] [2] and [3] to your older kernel and see how it goes.
That should make it work, but there are also some race condition fixes
( [4] [5] [6]) which should also be applied.
Alan.
[1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a8ab5d58b0238b8199cc699b8dff7c5e1da24138
[2] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=29129a98e6fc892d63bf7b8efcb458a258fe1683
[3] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c29771c2d8ceb907ed45eb8c7fc0450308140aca
[4] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d20d5ffab92f00188f360c44c791a5ffb988247c
[5] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e42dee9a99a3ecd32b5c027e8f7411fb5bc11eb6
[6] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=cb174681a9ececa6702f114b85bdf82144b6a5af
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
