linux-kernel - Re: [PATCH v2] hwmon: corsair-cpro: fix ccp

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Date:   Mon, 17 Aug 2020 08:35:33 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marius Zachmann <mail@...iuszachmann.de>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org
Subject: Re: [PATCH v2] hwmon: corsair-cpro: fix ccp_probe, add delay [HID
 related]

On Mon, Aug 17, 2020 at 09:00:40AM +0200, Marius Zachmann wrote:
> Possibly because of the changes in usbhid/hid-core.c the first
> raw input report is not received during ccp_probe function and it will
> timeout. I am not sure, whether this behaviour is expected after
> hid_device_io_start or if I am missing something.
> As a solution this adds msleep(50) to ccp_probe so that all initial
> input reports can be received.
> 
> Signed-off-by: Marius Zachmann <mail@...iuszachmann.de>

Let's just ask the HID maintainers. Is this expected, and the correct fix ?

Thanks,
Guenter

> ---
> v2:
> - fix accidentally deleted comment
> 
> ---
>  drivers/hwmon/corsair-cpro.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hwmon/corsair-cpro.c b/drivers/hwmon/corsair-cpro.c
> index 591929ec217a..c04fac1d820f 100644
> --- a/drivers/hwmon/corsair-cpro.c
> +++ b/drivers/hwmon/corsair-cpro.c
> @@ -10,6 +10,7 @@
> 
>  #include <linux/bitops.h>
>  #include <linux/completion.h>
> +#include <linux/delay.h>
>  #include <linux/hid.h>
>  #include <linux/hwmon.h>
>  #include <linux/kernel.h>
> @@ -513,6 +514,7 @@ static int ccp_probe(struct hid_device *hdev, const struct hid_device_id *id)
>  	init_completion(&ccp->wait_input_report);
> 
>  	hid_device_io_start(hdev);
> +	msleep(50); /* wait before events can be received */
> 
>  	/* temp and fan connection status only updates when device is powered on */
>  	ret = get_temp_cnct(ccp);
> --
> 2.28.0