Re: [PATCH] staging: greybus: hid: fix SET_REPORT return value

[Hao-Qun Huang]

On Jul 10, 2026 at 2:50 AM, Dan Carpenter <error27@xxxxxxxxx> wrote:
> The bug is not hard to understand, the issue is that this changes the
> function completely...  Was nothing checking the return before?

It gets checked.  The value flows unchanged through __hid_hw_raw_request()
to the callers, and they look at it two ways:

 - hidraw returns it straight to userspace (write(), HIDIOCSFEATURE),
   where it is the number of bytes transferred.

 - in-kernel SET_REPORT callers, some testing "ret < 0" (hid-multitouch,
   hid-sony), some testing "ret != size" (hid-gt683r, hid-lenovo,
   hid-razer).

So the old return 0 was wrong both ways: the first group had a failed
SET_REPORT masked as success, and the second saw every SET_REPORT as a
failure.  Returning the count or a negative errno is what GET already
does in this driver and what usbhid/i2c-hid/uhid return, so nothing
working with those relied on the 0.

Thanks,
Hao-Qun