linux-kernel - Re: [PATCH v2 2/3] HID: logitech-hidpp: Retry commands when device is busy

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Message-ID: <20230209145050.54ewn3zhjneium2h@mail.corp.redhat.com>
Date:   Thu, 9 Feb 2023 15:50:50 +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 v2 2/3] HID: logitech-hidpp: Retry commands when device
 is busy

On Feb 06 2023, Bastien Nocera wrote:
> Handle the busy error coming from the device or receiver. The
> documentation says a busy error can be returned when:
> "
> Device (or receiver) cannot answer immediately to this request
> for any reason i.e:
> - already processing a request from the same or another SW
> - pipe full
> "
> 
> Signed-off-by: Bastien Nocera <hadess@...ess.net>
> ---
> 
> Same as v1
> 
>  drivers/hid/hid-logitech-hidpp.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> index 1952d8d3b6b2..9e94026de437 100644
> --- a/drivers/hid/hid-logitech-hidpp.c
> +++ b/drivers/hid/hid-logitech-hidpp.c
> @@ -295,6 +295,7 @@ static int hidpp_send_message_sync(struct hidpp_device *hidpp,
>  	 */
>  	*response = *message;
>  
> +retry:
>  	ret = __hidpp_send_report(hidpp->hid_dev, message);
>  
>  	if (ret) {
> @@ -321,6 +322,10 @@ static int hidpp_send_message_sync(struct hidpp_device *hidpp,
>  			response->report_id == REPORT_ID_HIDPP_VERY_LONG) &&
>  			response->fap.feature_index == HIDPP20_ERROR) {
>  		ret = response->fap.params[1];
> +		if (ret == HIDPP20_ERROR_BUSY) {
> +			dbg_hid("%s:got busy hidpp 2.0 error %02X, retrying\n", __func__, ret);
> +			goto retry;

I must confess, I blocked a little bit there to decide whether or not
using goto here was OK.

But then I reliazed that there is no way to leave that function if the
device is buggy and constantly sends back ERROR_BUSY. So I am not very
found of the idea of having that got after all.

Would you mind respinning that patch with a bounded loop for the retries
instead of using a goto? I'd like the driver to give up after a few
retries if the device is not fair.

Cheers,
Benjamin

> +		}
>  		dbg_hid("%s:got hidpp 2.0 error %02X\n", __func__, ret);
>  		goto exit;
>  	}
> -- 
> 2.39.1
>