linux-kernel - Re: [PATCH] media: i2c: ov7740: implement get_mbus

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Date:   Wed, 3 Nov 2021 12:39:52 +0000
From:   <Eugen.Hristev@...rochip.com>
To:     <sakari.ailus@...ux.intel.com>
CC:     <akinobu.mita@...il.com>, <linux-media@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <jacopo@...ndi.org>
Subject: Re: [PATCH] media: i2c: ov7740: implement get_mbus_config

On 11/3/21 10:08 AM, Sakari Ailus wrote:
> Hi Eugen,
> 
> Thanks for the patch.
> 
> On Tue, Nov 02, 2021 at 05:30:08PM +0200, Eugen Hristev wrote:
>> Implement the get_mbus_config callback.
>> ov7740 is a parallel sensor, and according to datasheet, the register
>> REG12 controls the CCIR656 mode. This register is written to 0 in yuyv mode.
>> According to REG12[5] , CCIR656 mode, the behavior is:
>> CCIR656: disabled
>> REG28 controls the polarity of the signals. This register is unused.
>> The default behavior is then:
>> HSYNC polarity : positive
>> VSYNC polarity : positive
>> HREF polarity: positive
>>
> 
> Doesn't the receiver driver get this information from DT?
> 

Hi Sakari,

This patch comes as a result of my discussions with Jacopo, he advised 
to get mbus configuration via the get_mbus_config . I agree that this 
information can be taken from DT as you said.
In the end , my understanding is that get_mbus_config should be used 
only for runtime configuration which can change.
Thus, if all this information is static, then, I will proceed with 
obtaining it from DT, and you can disregard this patch, as it is not useful.

Thanks,
Eugen

>> Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
>> ---
>>   drivers/media/i2c/ov7740.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/media/i2c/ov7740.c b/drivers/media/i2c/ov7740.c
>> index 2539cfee85c8..f8a717aecb6f 100644
>> --- a/drivers/media/i2c/ov7740.c
>> +++ b/drivers/media/i2c/ov7740.c
>> @@ -873,12 +873,26 @@ static int ov7740_get_fmt(struct v4l2_subdev *sd,
>>        return ret;
>>   }
>>
>> +static int ov7740_get_mbus_config(struct v4l2_subdev *sd,
>> +                               unsigned int pad,
>> +                               struct v4l2_mbus_config *cfg)
>> +{
>> +     cfg->type = V4L2_MBUS_PARALLEL;
>> +     cfg->flags = V4L2_MBUS_MASTER | V4L2_MBUS_HSYNC_ACTIVE_HIGH |
>> +                  V4L2_MBUS_VSYNC_ACTIVE_HIGH |
>> +                  V4L2_MBUS_PCLK_SAMPLE_RISING |
>> +                  V4L2_MBUS_FIELD_EVEN_LOW | V4L2_MBUS_DATA_ACTIVE_HIGH;
>> +
>> +     return 0;
>> +}
>> +
>>   static const struct v4l2_subdev_pad_ops ov7740_subdev_pad_ops = {
>>        .enum_frame_interval = ov7740_enum_frame_interval,
>>        .enum_frame_size = ov7740_enum_frame_size,
>>        .enum_mbus_code = ov7740_enum_mbus_code,
>>        .get_fmt = ov7740_get_fmt,
>>        .set_fmt = ov7740_set_fmt,
>> +     .get_mbus_config = ov7740_get_mbus_config,
>>   };
>>
>>   static const struct v4l2_subdev_ops ov7740_subdev_ops = {
> 
> --
> Regards,
> 
> Sakari Ailus
>