Re: [PATCH 7/7] v4l: ti-vpe: Add crop support in VPE driver

[Archit Taneja <archit@ti.com>]

Hi Hans,

On Monday 03 March 2014 01:20 PM, Hans Verkuil wrote:
> Hi Archit!
>
> On 03/03/2014 08:33 AM, Archit Taneja wrote:
>> Add crop ioctl ops. For VPE, cropping only makes sense with the input to VPE, or
>> the V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE buffer type.
>>
>> For the CAPTURE type, a S_CROP ioctl results in setting the crop region as the
>> whole image itself, hence making crop dimensions same as the pix dimensions.
>>
>> Setting the crop successfully should result in re-configuration of those
>> registers which are affected when either source or destination dimensions
>> change, set_srcdst_params() is called for this purpose.
>>
>> Some standard crop parameter checks are done in __vpe_try_crop().
>
> Please use the selection ops instead: if you implement cropping with those then you'll
> support both the selection API and the old cropping API will be implemented by the v4l2
> core using the selection ops. Two for the price of one...


When using selection API, I was finding issues using the older cropping 
API. The v4l_s_crop() ioctl func assumes that "crop means compose for 
output devices". However, for a m2m device. It probably makes sense to 
provide the following configuration:

for V4L2_BUF_TYPE_VIDEO_OUTPUT (input to the mem to mem HW), use CROP 
target(to crop the input buffer)

and, for V4L2_BUF_TYPE_VIDEO_CAPTURE(output of the mem to mem HW), use 
COMPOSE target(to place the HW output into a larger region)

Don't you think forcing OUTPUT devices to 'COMPOSE' for older cropping 
API is a bit limiting?


Thanks,
Archit