Re: [PATCH v2] hwmon: corsair-cpro: fix ccp_probe, add delay [HID related]

Re: [PATCH v2] hwmon: corsair-cpro: fix ccp_probe, add delay [HID related]

[Guenter Roeck]

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@mariuszachmann.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

Re: [PATCH v2] hwmon: corsair-cpro: fix ccp_probe, add delay [HID related]

[Marius Zachmann]

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@mariuszachmann.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.

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
> 

Re: [PATCH v2] hwmon: corsair-cpro: fix ccp_probe, add delay [HID related]

[Guenter Roeck]

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@mariuszachmann.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
>>
> 
> 
> 
> 

Re: [PATCH v2] hwmon: corsair-cpro: fix ccp_probe, add delay [HID related]

[Jiri Kosina]

On Tue, 18 Aug 2020, 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@mariuszachmann.de>
> > 
> > Let's just ask the HID maintainers. Is this expected, and the correct fix ?
> 
> 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.

[ CCing Dmitry ]

Yeah, this problem popped out also in other contexts, where many Logitech 
devices didn't probe properly, because of the race where the first IRQ is 
dropped on the floor (after hid_device_io_start() happens, but before the 
50ms timeout passess), and report descriptor never gets parsed and 
populated.

As this is just a boot time micro-optimization, I am going to revert the 
patch for 5.9 now, and we can try to fix this properly for next merge 
window.

Thanks,

-- 
Jiri Kosina
SUSE Labs