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 11:05:19 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     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 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).

Cheers,
Benjamin

>
> > We should only list devices that need special handling, and the ones
> > that don't work once HID++ was probed unsuccessfully.
> >
> > >  so add it to the list of devices
> > > that are not handled by logitech-hidpp.
> > >
> > > Fixes: 532223c8ac57 ("HID: logitech-hidpp: Enable HID++ for all the
> > > Logitech Bluetooth devices")
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > ---
> > >  drivers/hid/hid-logitech-hidpp.c |    1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > Index: linux-pm/drivers/hid/hid-logitech-hidpp.c
> > > ===================================================================
> > > --- linux-pm.orig/drivers/hid/hid-logitech-hidpp.c
> > > +++ linux-pm/drivers/hid/hid-logitech-hidpp.c
> > > @@ -4274,6 +4274,7 @@ static const struct hid_device_id unhand
> > >         { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
> > > USB_DEVICE_ID_LOGITECH_HARMONY_PS3) },
> > >         /* Handled in hid-generic */
> > >         { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH,
> > > USB_DEVICE_ID_LOGITECH_DINOVO_EDGE_KBD) },
> > > +       { HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_LOGITECH, 0xb016) },
> > >         {}
> > >  };
>