linux-kernel - Re: [PATCH v1 2/2] HID: logitech-hidpp: Add Bluetooth Mouse M336/M337/M535 to unhandled_hidpp

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Date:   Wed, 7 Dec 2022 11:11:32 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Bastien Nocera <hadess@...ess.net>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Jiri Kosina <jikos@...nel.org>,
        Filipe Laíns <lains@...eup.net>,
        linux-input@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Thorsten Leemhuis <regressions@...mhuis.info>
Subject: Re: [PATCH v1 2/2] HID: logitech-hidpp: Add Bluetooth Mouse
 M336/M337/M535 to unhandled_hidpp_devices[]

On Wed, Dec 7, 2022 at 11:05 AM Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
>
> On Wed, Dec 7, 2022 at 10:47 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > On Wed, Dec 7, 2022 at 10:29 AM Bastien Nocera <hadess@...ess.net> wrote:
> > >
> > > On Wed, 2022-12-07 at 10:12 +0100, Rafael J. Wysocki wrote:
> > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > >
> > > > Evidently, Logitech Bluetooth Mouse M336/M337/M535 (0xb016) does not
> > > > work when HID++ is enabled for it,
> > >
> > > This needs the output of the hidpp-list-features tool mentioned earlier
> > > in the thread so we can avoid words like "evidently" and provide
> > > concrete proof.
> >
> > Well, so point me to a binary of this, please.
> >
> > > But why is it needed in this case?
> >
> > Because it doesn't work otherwise.
> >
> > > We purposefully try to avoid blanket
> > > blocklists. The lack of HID++ can be probed, so the device should work
> > > just as it used to (if the fallback code works).
> >
> > No, because the hid-generic driver has no way to check that the probe
> > function of your driver fails for this particular device.  The probing
> > of hid-generic will fail so long as the device matches the device ID
> > list of any specific HID driver.  With patch [1/2] from this series
> > applied this is unless that specific driver has a ->match() callback
> > rejecting the given device.
> >
> > You'd need a list of drivers that have been tried and failed somewhere
> > for that and AFAICS no such list is present in the code.
>
> That is the reason why I never wanted to enable HID++ on all Logitech
> mice, and this comes back to bite us at the worst time possible, right
> before the merge window opens :(
>
> >
> > So a minimum fix for 6.1 that actually works for me is to add the
> > non-working device to the blocklist.  More sophisticated stuff can be
> > done later.
>
> Agree, but OTOH, Rafael, your mouse is not brand new AFAICT, so I am
> worried that you won't be the only one complaining we just killed
> their mouse.
> So I think the even wiser solution would be to delay (and so revert in
> 6.1 or 6.2) the 2 patches that enable hid++ on all logitech mice
> (8544c812e43ab7bdf40458411b83987b8cba924d and
> 532223c8ac57605a10e46dc0ab23dcf01c9acb43).

Obviously that would work for me too, so it's your call.

Thanks!