Re: [PATCH v3] HID: i2c-hid: Revert to await reset ACK before reading report descriptor

[Jiri Kosina <jikos@kernel.org>]

On Tue, 2 Apr 2024, Mark Pearson wrote:

> On Tue, Apr 2, 2024, at 7:10 AM, Hans de Goede wrote:
> > From: Kenny Levinsen <kl@kl.wtf>
> >
> > In af93a167eda9, i2c_hid_parse was changed to continue with reading the
> > report descriptor before waiting for reset to be acknowledged.
> >
> > This has lead to two regressions:
> >
> > 1. We fail to handle reset acknowledgment if it happens while reading
> >    the report descriptor. The transfer sets I2C_HID_READ_PENDING, which
> >    causes the IRQ handler to return without doing anything.
> >
> >    This affects both a Wacom touchscreen and a Sensel touchpad.
> >
> > 2. On a Sensel touchpad, reading the report descriptor this quickly
> >    after reset results in all zeroes or partial zeroes.
> >
> > The issues were observed on the Lenovo Thinkpad Z16 Gen 2.
> >
> > The change in question was made based on a Microsoft article[0] stating
> > that Windows 8 *may* read the report descriptor in parallel with
> > awaiting reset acknowledgment, intended as a slight reset performance
> > optimization. Perhaps they only do this if reset is not completing
> > quickly enough for their tastes?
> >
> > As the code is not currently ready to read registers in parallel with a
> > pending reset acknowledgment, and as reading quickly breaks the report
> > descriptor on the Sensel touchpad, revert to waiting for reset
> > acknowledgment before proceeding to read the report descriptor.
> >
> > [0]: 
> > https://learn.microsoft.com/en-us/windows-hardware/drivers/hid/plug-and-play-support-and-power-management
> >
> > Fixes: af93a167eda9 ("HID: i2c-hid: Move i2c_hid_finish_hwreset() to 
> > after reading the report-descriptor")
> > Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2271136
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Kenny Levinsen <kl@kl.wtf>
> > Link: https://lore.kernel.org/r/20240331182440.14477-1-kl@kl.wtf
> > [hdegoede@redhat.com Drop no longer necessary abort_reset error exit 
> > path]
> > Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[ .. snip .. ]
> Tested on my Z13 G2 system and confirmed this fixes the issue.
> 
> Tested-by: Mark Pearson <mpearson-lenovo@squebb.ca>

Applied to hid.git#for-6.9/upstream-fixes. Thanks,

-- 
Jiri Kosina
SUSE Labs