linux-kernel - Re: [PATCH] HID: logitech-hidpp: Handle timeout differently from busy

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Date:   Sat, 3 Jun 2023 09:17:48 -0400
From:   Mark Lord <mlord@...ox.com>
To:     Jiri Kosina <jikos@...nel.org>, Bastien Nocera <hadess@...ess.net>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        "Peter F . Patel-Schneider" <pfpschneider@...il.com>,
        Filipe Laíns <lains@...eup.net>,
        Nestor Lopez Casado <nlopezcasad@...itech.com>
Subject: Re: [PATCH] HID: logitech-hidpp: Handle timeout differently from busy

On 2023-06-03 08:41 AM, Jiri Kosina wrote:
> On Wed, 31 May 2023, Jiri Kosina wrote:
> 
>>> If an attempt at contacting a receiver or a device fails because the
>>> receiver or device never responds, don't restart the communication, only
>>> restart it if the receiver or device answers that it's busy, as originally
>>> intended.
>>>
>>> This was the behaviour on communication timeout before commit 586e8fede795
>>> ("HID: logitech-hidpp: Retry commands when device is busy").
>>>
>>> This fixes some overly long waits in a critical path on boot, when
>>> checking whether the device is connected by getting its HID++ version.
>>>
>>> Signed-off-by: Bastien Nocera <hadess@...ess.net>
>>> Suggested-by: Mark Lord <mlord@...ox.com>
>>> Fixes: 586e8fede795 ("HID: logitech-hidpp: Retry commands when device is busy")
>>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217412
>>> ---
>>>  drivers/hid/hid-logitech-hidpp.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
>>> index 0fcfd85fea0f..2246044b1639 100644
>>> --- a/drivers/hid/hid-logitech-hidpp.c
>>> +++ b/drivers/hid/hid-logitech-hidpp.c
>>> @@ -314,6 +314,7 @@ static int hidpp_send_message_sync(struct hidpp_device *hidpp,
>>>  			dbg_hid("%s:timeout waiting for response\n", __func__);
>>>  			memset(response, 0, sizeof(struct hidpp_report));
>>>  			ret = -ETIMEDOUT;
>>> +			goto exit;
>>>  		}
>>>  
>>
>> I have applied this even before getting confirmation from the reporters in 
>> bugzilla, as it's the right thing to do anyway.
> 
> Unfortunately it doesn't seem to cure the reported issue (while reverting 
> 586e8fede79 does): https://bugzilla.kernel.org/show_bug.cgi?id=217523#c2

I wonder if this code could be re-worked to not even do this (waiting)
from the _probe() function?  It ought to be able to throw it on a workqueue
or something, rather than stalling system boot for a minimum of 5-seconds
(or much longer as as-is).
-- 
Mark Lord