linux-kernel - Re: [PATCH v11 2/7] cx25840: g_std operation really implements querystd operation

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Message-ID: <2b34d7d0-18b7-d403-4186-6a851c1520eb@maciej.szmigiero.name>
Date:   Mon, 29 Apr 2019 13:41:39 +0200
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Michael Krufky <mkrufky@...uxtv.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Andy Walls <awalls@...metrocast.net>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v11 2/7] cx25840: g_std operation really implements
 querystd operation

On 29.04.2019 10:05, Hans Verkuil wrote:
> On 4/27/19 4:50 PM, Maciej S. Szmigiero wrote:
>> cx25840 driver g_std operation queries the currently detected video signal,
>> however this is what querystd operation should do, so let's rename the
>> handler.
>>
>> None of the existing cx25840 driver users ever called the g_std operation,
>> one of them calls querystd on each of its subdevs but then the result is
>> only used to implement VIDIOC_QUERYSTD (as it should).
>>
>> Signed-off-by: Maciej S. Szmigiero <mail@...iej.szmigiero.name>
>> ---
>>  drivers/media/i2c/cx25840/cx25840-core.c | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/i2c/cx25840/cx25840-core.c b/drivers/media/i2c/cx25840/cx25840-core.c
>> index 0bf30222cf93..2bcaf239b0d2 100644
>> --- a/drivers/media/i2c/cx25840/cx25840-core.c
>> +++ b/drivers/media/i2c/cx25840/cx25840-core.c
>> @@ -1772,7 +1772,7 @@ static int cx25840_s_stream(struct v4l2_subdev *sd, int enable)
>>  }
>>  
>>  /* Query the current detected video format */
>> -static int cx25840_g_std(struct v4l2_subdev *sd, v4l2_std_id *std)
>> +static int cx25840_querystd(struct v4l2_subdev *sd, v4l2_std_id *std)
>>  {
>>  	struct i2c_client *client = v4l2_get_subdevdata(sd);
>>  
>> @@ -1800,8 +1800,9 @@ static int cx25840_g_std(struct v4l2_subdev *sd, v4l2_std_id *std)
>>  	u32 fmt = (cx25840_read4(client, 0x40c) >> 8) & 0xf;
>>  	*std = stds[ fmt ];
>>  
>> -	v4l_dbg(1, cx25840_debug, client, "g_std fmt = %x, v4l2_std_id = 0x%x\n",
>> -		fmt, (unsigned int)stds[ fmt ]);
>> +	v4l_dbg(1, cx25840_debug, client,
>> +		"querystd fmt = %x, v4l2_std_id = 0x%x\n",
>> +		fmt, (unsigned int)stds[fmt]);
>>  
>>  	return 0;
>>  }
>> @@ -5081,7 +5082,7 @@ static const struct v4l2_subdev_audio_ops cx25840_audio_ops = {
>>  
>>  static const struct v4l2_subdev_video_ops cx25840_video_ops = {
>>  	.s_std = cx25840_s_std,
>> -	.g_std = cx25840_g_std,
>> +	.querystd = cx25840_querystd,
>>  	.s_routing = cx25840_s_video_routing,
>>  	.s_stream = cx25840_s_stream,
>>  	.g_input_status = cx25840_g_input_status,
>>
> 
> Hmm, you are right, g_std really implements querystd. I wondered why this wasn't
> noticed before, and it appears that no bridge driver ever calls the g_std op of the
> cx25840 driver. It's all handled inside the bridge driver itself.
> 
> Can you add a new cx25840_g_std() op here that just returns state->std?
> 
> That would make much more sense.
> 
> You also need to use g_std in patch 6/7 (see my comments there)

Will do, but a small comment here:
Currently, when somebody passes a set of multiple standards to s_std,
let's say V4L2_STD_ALL the chip isn't configured for "every standard
possible".

It is set for a specific, single standard from this set of standards.
There is a "if" tree at the begging of set_v4lstd() that implements,
effectively, a list of priorities when selecting a single standard
from a set of multiple.

That's why I think the incoming standard should be selected upfront
according to this priority list in s_std handler and only this
effective value should be set in state->std so g_std actually
returns what the device is set for.

> Regards,
> 
> 	Hans
> 

Thanks,
Maciej