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

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Date:   Tue, 18 Aug 2020 06:42:38 -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 8/18/20 6:12 AM, Marius Zachmann wrote:
> On 18.08.20 at 17:35:33 CEST, Guenter Roeck wrote
>> 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
>>
> 
> This seems to be a problem with "HID: usbhid: do not sleep when opening
> device". There is a bug report with some Logitech devices at the correct
> thread. These drivers also use hid_device_io_start and fail. Seems to me,
> this is the same problem and I retract this (not so beautiful) fix until
> this is sorted out.
> 

I even was involved in that patch. Sigh.

Guenter

> Thanks,
> Marius
> 
>>> ---
>>> 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
>>
> 
> 
> 
>