Re: Adding a control for Sensor Orientation

[Hans de Goede <hdegoede@redhat.com>]

Hans Verkuil wrote:
>>> If you want to add two bits with
>>> mount information, feel free. But don't abuse them for pivot
>>> information.
>>> If you want that, then add another two bits for the rotation:
>>>
>>> #define V4L2_BUF_FLAG_VFLIP     0x0400
>>> #define V4L2_BUF_FLAG_HFLIP     0x0800
>>>
>>> #define V4L2_BUF_FLAG_PIVOT_0   0x0000
>>> #define V4L2_BUF_FLAG_PIVOT_90  0x1000
>>> #define V4L2_BUF_FLAG_PIVOT_180 0x2000
>>> #define V4L2_BUF_FLAG_PIVOT_270 0x3000
>>> #define V4L2_BUF_FLAG_PIVOT_MSK 0x3000
>>>
>> Ok, this seems good. But if we want to distinguish between static sensor
>> mount
>> information, and dynamic sensor orientation changing due to pivotting,
>> then I
>> think we should only put the pivot flags in the buffer flags, and the
>> static
>> flags should be in the VIDIOC_QUERYCAP capabilities flag, what do you
>> think of
>> that?
> 
> That's for driver global information. This type of information is
> input-specific (e.g. input 1 might be from an S-Video input and does not
> require v/hflip, and input 2 is from a sensor and does require v/hflip).
> So struct v4l2_input seems a good place for it.
> 
> Looking at v4l2_input there is a status field, but the status information
> is valid for the current input only. We can:
> 
> 1) add flags here and only set the mounting information for the current
> input,
> 
> 2) add flags here and document that these flags are valid for any input,
> not just the current, or:
> 
> 3) take one of the reserved fields and turn that into a 'flags' field that
> can be used for static info about the input.
> 
> To be honest, I prefer 3.
> 
> The same can be done for v4l2_output should it become necessary in the
> future.
> 
> Actually, pivot information could be stored here as well. Doing that makes
> it possible to obtain the orientation without needing to start a capture,
> and makes it possible to be used (although awkwardly) with the read()
> interface.
> 
> You still want to report this information in v4l2_buffer as well since it
> can change on the fly.
> 

Sounds good to me.

Regards,

Hans