Re: [PATCH 20/25] media: ov5647: Program mode only if it has changed

[Dafna Hirschfeld <dafna.hirschfeld@collabora.com>]

On 30.06.20 09:43, Jacopo Mondi wrote:
> Hi Dafna,
> 
> On Mon, Jun 29, 2020 at 07:48:16PM +0200, Dafna Hirschfeld wrote:
>>
>>
>> On 23.06.20 18:55, Jacopo Mondi wrote:
>>> Store in the driver structure a pointer to the currently applied mode
>>> and program a new one at s_stream(1) time only if it has changed.
>>
>> Hi,
>> I think this can be more readably implemented with a 'is_streaming' boolean
>> field.
> 
> How would you like to use an 'is_streaming' flag to decide if the
> sensor mode has to be updated ?

since 'current_mode' is set to NULL upon `ov5647_stream_off`
and you return from 'ov5647_set_stream' immediately if 'mode == current_mode'
it seem very similar to returning immediately from 'ov5647_set_stream' if the
device is currently streaming.

But actually in this patch it seems to be possible to change the mode
while streaming, if the callbacks are executed:

s_stream(1)
s_fmt
s_stream(1)

which is maybe a bug?

Thanks,
Dafna

> 
> Thanks
>     j
> 
> 
>>
>> Thanks,
>> Dafna
>>
>>>
>>> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
>>> ---
>>>    drivers/media/i2c/ov5647.c | 16 +++++++++++++++-
>>>    1 file changed, 15 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/media/i2c/ov5647.c b/drivers/media/i2c/ov5647.c
>>> index 39e320f321bd8..ac114269e1c73 100644
>>> --- a/drivers/media/i2c/ov5647.c
>>> +++ b/drivers/media/i2c/ov5647.c
>>> @@ -96,6 +96,7 @@ struct ov5647 {
>>>    	bool				clock_ncont;
>>>    	struct v4l2_ctrl_handler	ctrls;
>>>    	struct ov5647_mode		*mode;
>>> +	struct ov5647_mode		*current_mode;
>>>    };
>>>    static inline struct ov5647 *to_sensor(struct v4l2_subdev *sd)
>>> @@ -750,9 +751,13 @@ static int ov5647_set_virtual_channel(struct v4l2_subdev *sd, int channel)
>>>    static int ov5647_set_mode(struct v4l2_subdev *sd)
>>>    {
>>>    	struct i2c_client *client = v4l2_get_subdevdata(sd);
>>> +	struct ov5647 *sensor = to_sensor(sd);
>>>    	u8 resetval, rdval;
>>>    	int ret;
>>> +	if (sensor->mode == sensor->current_mode)
>>> +		return 0;
>>> +
>>>    	ret = ov5647_read(sd, OV5647_SW_STANDBY, &rdval);
>>>    	if (ret < 0)
>>>    		return ret;
>>> @@ -778,6 +783,8 @@ static int ov5647_set_mode(struct v4l2_subdev *sd)
>>>    			return ret;
>>>    	}
>>> +	sensor->current_mode = sensor->mode;
>>> +
>>>    	return 0;
>>>    }
>>> @@ -816,6 +823,7 @@ static int ov5647_stream_on(struct v4l2_subdev *sd)
>>>    static int ov5647_stream_off(struct v4l2_subdev *sd)
>>>    {
>>> +	struct ov5647 *sensor = to_sensor(sd);
>>>    	int ret;
>>>    	ret = ov5647_write(sd, OV5647_REG_MIPI_CTRL00, MIPI_CTRL00_CLOCK_LANE_GATE |
>>> @@ -827,7 +835,13 @@ static int ov5647_stream_off(struct v4l2_subdev *sd)
>>>    	if (ret < 0)
>>>    		return ret;
>>> -	return ov5647_write(sd, OV5640_REG_PAD_OUT, 0x01);
>>> +	ret = ov5647_write(sd, OV5640_REG_PAD_OUT, 0x01);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	sensor->current_mode = NULL;
>>> +
>>> +	return 0;
>>>    }
>>>    static int set_sw_standby(struct v4l2_subdev *sd, bool standby)
>>>