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

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Message-ID: <39fcf3b6b0954873d5e7cdcabcd26a63178619b8.camel@hadess.net>
Date:   Wed, 25 Jan 2023 12:52:41 +0100
From:   Bastien Nocera <hadess@...ess.net>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
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 Wed, 2023-01-25 at 11:18 +0100, Benjamin Tissoires wrote:
> 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.

>From what I can tell, this would mean restarting the connection in case
hidpp_unifying_init() did anything, right?

I'll test this out and update the patch.

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 4547e9580101..e0c28257f598 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -4392,8 +4392,10 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
        /* Allow incoming packets */
        hid_device_io_start(hdev);
 
-       if (hidpp->quirks & HIDPP_QUIRK_UNIFYING)
-               hidpp_unifying_init(hidpp);
+       if (hidpp->quirks & HIDPP_QUIRK_UNIFYING) {
+               if (hidpp_unifying_init(hidpp) == 0)
+                       will_restart = true;
+       }
 
        connected = hidpp_root_get_protocol_version(hidpp) == 0;
        atomic_set(&hidpp->connected, connected);