Re: [PATCH/RFC v2] HID: logitech: read all 32 bits of report type bitfield

On 2012-05-11 04:39, Jonathan Nieder wrote:

From: Nestor Lopez Casado <redacted>

On big-endian systems (e.g., Apple PowerBook), trying to use a
logitech wireless mouse with the Logitech Unifying Receiver does not
work with v3.2 and later kernels.  The device doesn't show up in
/dev/input.  Older kernels work fine.

That is because the new hid-logitech-dj driver claims the device.  The
device arrival notification appears:

	20 00 41 02 00 00 00 00 00 00 00 00 00 00 00

and we read the report_types bitfield (02 00 00 00) to find out what
kind of device it is.  Unfortunately the driver only reads the first 8
bits and treats that value as a 32-bit little-endian number, so on a
powerpc the report type seems to be 0x02000000 and is not recognized.

Even on little-endian machines, connecting a media center remote
control (report type 00 01 00 00) with this driver loaded would
presumably fail for the same reason.

Fix both problems by using get_unaligned_le32() to read all four
bytes, which is a little clearer anyway.  After this change, the
wireless mouse works on Hugo's PowerBook again.

Addresses http://bugs.debian.org/671292

[jn: with commit message and tweaked to use get_unaligned instead of
 copying onto the stack]

Reported-by: Hugo Osvaldo Barrera <redacted>
Signed-off-by: Jonathan Nieder <redacted>
Cc: <redacted>
---
Change since v1: fixed attribution.

I had been wondering why the patch you sent before didn't fix Hugo's
problem while the effectively identical patch I sent did.  The only
explanation I can think of is an error introduced in applying the
patch by hand.

<patch snipped>

I'd hate to think I screwed up applying such a simple patch, but it's
the only thing I can think of as well.

Thanks again to both of you for your time and effort, and for your
timely responses on this issue!

I hope this makes it to the main branch soon!

Cheers, and good luck to both,

-- 
Hugo Osvaldo Barrera