Re: Bug#986561: linux: Regression in drivers/hid/hid-dr.c causing horizontal D-pad to malfunction on SNES joystick

[Salvatore Bonaccorso <carnil@debian.org>]

Hi Ioan-Adrian,

On Wed, Apr 07, 2021 at 02:47:24PM +0200, Alessandro Grassi wrote:
> Source: linux
> Severity: normal
> Tags: upstream
> X-Debbugs-Cc: alessandro@aggro.it
> 
> Greetings,
> 
> I am encountering the issue described in this thread[1], using a gamepad identified as "DragonRise" with USB ID 0079:0011.
> 
> The joypad works as intended except for the D-pad: up and down are detected in jstest (though misinterpreted: the input graph shows the points in the left up/down corners instead of the center), the left and right buttons are completely ignored.
> 
> Running 'input-events' shows events 0/127 and 255/127 on up and down respectively, nothing at all on left and right.
> 
> I was able to identify that the misbehaviour was caused by this commit[2] on the kernel source tree. To determine this I have rebuilt the Debian kernel using hid-dr.c from the previous commit[3] and loaded hid-dr.ko manually, with which the gamepad worked as intended. I have replaced the file again with the one from the breaking commit iself ([2]) and the behaviour was again broken.
> 
> Furthermore, to confirm that that was the breaking commit, I have commented line 315 (the input mapping one in the struct) from the current Debian source tree and rebuilt it, the joypad works as it should.
> 
> Regards,
> Alessandro
> 
> [1]: https://retropie.org.uk/forum/topic/25657/controler-issue-no-left-and-right-not-working-at-all
> [2]: https://github.com/torvalds/linux/commit/e15944099870f374ca7efc62f98cf23ba272ef43
> [3]: https://github.com/torvalds/linux/commit/313726cad3b68039c8e4dcad5a2840a0d375678c

A user in Debian reported that e15944099870 ("HID: hid-dr: add input
mapping for axis selection") introduced a regression, described above.

Does this ring some bell to you?

Regards,
Salvatore