Re: [PATCH v2 14/15] HID: ft260: i2c: fix i2c_reset sysfs store return value

[sashiko-bot@kernel.org]

> A sysfs store must return the number of bytes it consumed. kernfs
> hands that value straight to write(2). i2c_reset_store() returns
> whatever ft260_i2c_reset() returns, which is the length of the
> feature report it sent, 2, not 0. The "return count" below it never
> runs, so every write to i2c_reset returns 2 whatever its size.
> 
> A write of two bytes is right by coincidence, because the report is
> two bytes long. A caller that leaves out the newline, as C and Python
> code usually does, writes one byte and gets 2 back, which is more
> than it asked for:
> 
>   echo -n 1 > i2c_reset   1 byte, write() returns 2, bash ignores it
>   printf 1  > i2c_reset   1 byte, dash reports an I/O error
>   echo 1    > i2c_reset   2 bytes, correct by coincidence
> 
> Return 0 from ft260_i2c_reset() on success. The value is discarded by
> its other callers, ft260_hid_output_report_check_status(),
> ft260_i2c_probe() and ft260_i2c_abort(), whose own four callers
> discard it as well.
> 
> Fixes: 6a82582d9fa4 ("HID: ft260: add usb hid to i2c host bridge driver")
> Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261030223637.86907-1-michael.zaidman@gmail.com?part=14