linux-kernel - Re: [PATCH 2/3] HID: logitech-hidpp: Don't restart communication if not necessary

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Date:   Wed, 25 Jan 2023 11:18:05 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Bastien Nocera <hadess@...ess.net>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiri Kosina <jikos@...nel.org>,
        "Peter F . Patel-Schneider" <pfpschneider@...il.com>,
        Filipe Laíns <lains@...eup.net>,
        Nestor Lopez Casado <nlopezcasad@...itech.com>
Subject: Re: [PATCH 2/3] HID: logitech-hidpp: Don't restart communication if
 not necessary

On Tue, Jan 24, 2023 at 6:20 PM Bastien Nocera <hadess@...ess.net> wrote:
>
> On Tue, 2022-12-20 at 10:22 +0100, Bastien Nocera wrote:
> > Don't stop and restart communication with the device unless we need
> > to
> > modify the connect flags used because of a device quirk.
>
> FIWW, Andreas Bergmeier told me off-list that this fixed their problem
> with the Litra Glow not connecting properly.
>
> Would be great to have reviews on this and my other HID++ patches.

Sigh. I reviewed the patches just now (well, v2 at least), and thought
I better give a shot at it before merging, and it turns out that this
patch breaks the Unifying receivers.

Without it, each device presented to the user space has a proper name:

logitech-hidpp-device 0003:046D:4041.001C: input,hidraw15: USB HID
v1.11 Keyboard [Logitech MX Master] on usb-0000:01:00.0-4/input2:5

But with it, I get:

logitech-hidpp-device 0003:046D:4041.0024: input,hidraw8: USB HID
v1.11 Keyboard [Logitech Wireless Device PID:4041] on
usb-0000:00:14.0-8.2.4/input2:5

This is because we present the device to the userspace before being
able to fetch the name from the receiver.

I think we should make that connect/disconnect a special case of the
receivers too. Or maybe if the bus is not Bluetooth or USB, do the
disconnect/reconnect.

Cheers,
Benjamin

>
> Cheers
>
> > ---
> >  drivers/hid/hid-logitech-hidpp.c | 31 +++++++++++++++++++-----------
> > -
> >  1 file changed, 19 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-
> > logitech-hidpp.c
> > index 7f9187201913..b4e4a8c79c75 100644
> > --- a/drivers/hid/hid-logitech-hidpp.c
> > +++ b/drivers/hid/hid-logitech-hidpp.c
> > @@ -4310,6 +4310,7 @@ static int hidpp_probe(struct hid_device *hdev,
> > const struct hid_device_id *id)
> >         bool connected;
> >         unsigned int connect_mask = HID_CONNECT_DEFAULT;
> >         struct hidpp_ff_private_data data;
> > +       bool will_restart = false;
> >
> >         /* report_fixup needs drvdata to be set before we call
> > hid_parse */
> >         hidpp = devm_kzalloc(&hdev->dev, sizeof(*hidpp), GFP_KERNEL);
> > @@ -4360,6 +4361,9 @@ static int hidpp_probe(struct hid_device *hdev,
> > const struct hid_device_id *id)
> >                         return ret;
> >         }
> >
> > +       if (hidpp->quirks & HIDPP_QUIRK_DELAYED_INIT)
> > +               will_restart = true;
> > +
> >         INIT_WORK(&hidpp->work, delayed_work_cb);
> >         mutex_init(&hidpp->send_mutex);
> >         init_waitqueue_head(&hidpp->wait);
> > @@ -4374,7 +4378,7 @@ static int hidpp_probe(struct hid_device *hdev,
> > const struct hid_device_id *id)
> >          * Plain USB connections need to actually call start and open
> >          * on the transport driver to allow incoming data.
> >          */
> > -       ret = hid_hw_start(hdev, 0);
> > +       ret = hid_hw_start(hdev, will_restart ? 0 : connect_mask);
> >         if (ret) {
> >                 hid_err(hdev, "hw start failed\n");
> >                 goto hid_hw_start_fail;
> > @@ -4411,6 +4415,7 @@ static int hidpp_probe(struct hid_device *hdev,
> > const struct hid_device_id *id)
> >                         hidpp->wireless_feature_index = 0;
> >                 else if (ret)
> >                         goto hid_hw_init_fail;
> > +               ret = 0;
> >         }
> >
> >         if (connected && (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP)) {
> > @@ -4425,19 +4430,21 @@ static int hidpp_probe(struct hid_device
> > *hdev, const struct hid_device_id *id)
> >
> >         hidpp_connect_event(hidpp);
> >
> > -       /* Reset the HID node state */
> > -       hid_device_io_stop(hdev);
> > -       hid_hw_close(hdev);
> > -       hid_hw_stop(hdev);
> > +       if (will_restart) {
> > +               /* Reset the HID node state */
> > +               hid_device_io_stop(hdev);
> > +               hid_hw_close(hdev);
> > +               hid_hw_stop(hdev);
> >
> > -       if (hidpp->quirks & HIDPP_QUIRK_NO_HIDINPUT)
> > -               connect_mask &= ~HID_CONNECT_HIDINPUT;
> > +               if (hidpp->quirks & HIDPP_QUIRK_NO_HIDINPUT)
> > +                       connect_mask &= ~HID_CONNECT_HIDINPUT;
> >
> > -       /* Now export the actual inputs and hidraw nodes to the world
> > */
> > -       ret = hid_hw_start(hdev, connect_mask);
> > -       if (ret) {
> > -               hid_err(hdev, "%s:hid_hw_start returned error\n",
> > __func__);
> > -               goto hid_hw_start_fail;
> > +               /* Now export the actual inputs and hidraw nodes to
> > the world */
> > +               ret = hid_hw_start(hdev, connect_mask);
> > +               if (ret) {
> > +                       hid_err(hdev, "%s:hid_hw_start returned
> > error\n", __func__);
> > +                       goto hid_hw_start_fail;
> > +               }
> >         }
> >
> >         if (hidpp->quirks & HIDPP_QUIRK_CLASS_G920) {
>