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From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
To: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: "Janusz Krzysztofik" <jmkrzyszt@gmail.com>,
	"Linux Media Mailing List" <linux-media@vger.kernel.org>,
	"Niklas Söderlund" <niklas.soderlund@ragnatech.se>
Subject: Re: [PATCH for v5.3] v4l2-subdev: fix regression in check_pad()
Date: Sat, 29 Jun 2019 15:08:23 +0200	[thread overview]
Message-ID: <a4d4f164-0b9d-0917-3a48-fc97ae6730bf@xs4all.nl> (raw)
In-Reply-To: <afc93b30-f91a-2bf0-6793-08efca59a300@xs4all.nl>

On 6/29/19 2:57 PM, Hans Verkuil wrote:
> On 6/29/19 2:06 PM, Janusz Krzysztofik wrote:
>> Hi Hans,
>>
>> On Saturday, June 29, 2019 12:00:24 P.M. CEST Hans Verkuil wrote:
>>> sd->entity.graph_obj.mdev can be NULL when this function is called, and
>>> that breaks existing drivers (rcar-vin, but probably others as well).
>>>
>>> Check if sd->entity.num_pads is non-zero instead since that doesn't depend
>>> on mdev.
>>>
>>> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>>> Reported-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
>>> Fixes: a8fa55078a77 ("media: v4l2-subdev: Verify arguments in
>>> v4l2_subdev_call()") ---
>>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c
>>> b/drivers/media/v4l2-core/v4l2-subdev.c index 21fb90d66bfc..bc32fc1e0c0b
>>> 100644
>>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>>> @@ -124,16 +124,11 @@ static inline int check_which(__u32 which)
>>>  static inline int check_pad(struct v4l2_subdev *sd, __u32 pad)
>>>  {
>>>  #if defined(CONFIG_MEDIA_CONTROLLER)
>>> -	if (sd->entity.graph_obj.mdev) {
>>> -		if (pad >= sd->entity.num_pads)
>>> -			return -EINVAL;
>>> -		return 0;
>>> -	}
>>> +	if (sd->entity.num_pads)
>>
>> This reverts a change introduced on Sakari's request in v7 of the series which 
>> is the source of the regression.  The intention was to fail if num_pads == 0 
>> on a valid media entity. Maybe we should still keep that restriction and fail 
>> in case mdev is not NULL? In other words: 
>>
>> -	if (sd->entity.num_pads)
>> +	if (sd->entity.num_pads || sd->entity.graph_obj.mdev)
> 
> If an entity has no pads, then it doesn't have pad ops either and this function
> would never be called.

Sakari, do you think it is ever possible that an entity may have pad ops,
but num_pads goes at some point to 0?

If so, then we can check for sd->entity.function != 0. All MC subdevs must
set that to a non-0 value, otherwise the core will issue a WARN_ON. I think
it is the only reliable indicator that can be used.

Regards,

	Hans

> 
>>
>> Thanks,
>> Janusz
>>
>>> +		return pad >= sd->entity.num_pads ? -EINVAL : 0;
>>
>> This and below look like coding style changes, not related strictly to the 
>> merit.  Shouldn't they rather be split into a separate patch?
> 
> I'll post a v2, the diff is a lot smaller. I might post a follow-up patch
> to use ? : since that's a lot shorter code.
> 
> Regards,
> 
> 	Hans
> 
>>
>> BTW, the current coding style follows original implementation of check_* 
>> functions present before that series was introduced.  Maybe it would be better 
>> to keep them unified, i.e., either as is or all updated with the new style.
>>
>> Thanks,
>> Janusz
>>
>>>  #endif
>>>  	/* allow pad 0 on subdevices not registered as media entities */
>>> -	if (pad > 0)
>>> -		return -EINVAL;
>>> -	return 0;
>>> +	return pad ? -EINVAL : 0;
>>>  }
>>>
>>>  static int check_cfg(__u32 which, struct v4l2_subdev_pad_config *cfg)
>>
>>
>>
>>
> 


  reply	other threads:[~2019-06-29 13:08 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-29 10:00 [PATCH for v5.3] v4l2-subdev: fix regression in check_pad() Hans Verkuil
2019-06-29 11:33 ` Niklas Söderlund
2019-06-29 12:06 ` Janusz Krzysztofik
2019-06-29 12:57   ` Hans Verkuil
2019-06-29 13:08     ` Hans Verkuil [this message]
2019-07-01  7:50       ` Sakari Ailus
2019-07-01 21:24         ` Janusz Krzysztofik
2019-06-29 13:13     ` Janusz Krzysztofik
2019-06-29 13:19       ` Hans Verkuil
2019-06-29 12:59 Hans Verkuil

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