[PATCH v3] media: rkisp1: Remove min_queued_buffers

[Hans Verkuil]

On 10/29/24 12:29, Laurent Pinchart wrote:
> Hi Jacopo,
> 
> Thank you for the patch.
> 
> On Tue, Oct 29, 2024 at 09:21:16AM +0100, Jacopo Mondi wrote:
>> There apparently is no reason to require 3 queued buffers for RkISP1,
>> as the driver operates with a scratch buffer where data can be
>> directed to if there's no available buffer provided by userspace.
>>
>> Reduce the number of required buffers to 0 by removing the
>> initialization of min_queued_buffers, to allow applications to operate
>> by queueing capture buffers on-demand.
>>
>> Tested with libcamera, by operating with a single capture request. The
>> same request (and the associated capture buffer) gets recycled once
>> completed. This of course causes a frame rate drop but doesn't hinder
>> operations.
>>
>> Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Hans Verkuil <hverkuil at xs4all.nl>

Regards,

	Hans

> 
>> ---
>> v2->v3:
>> - Remove min_queued_buffers initialization
>>
>> v1->v2:
>> The first version of this patch set min_queued_buffers to 1, but setting it
>> to 0 doesn't compromise operations and it's even better as it allows application
>> to queue buffers to the capture devices on-demand. If a buffer is not provided
>> to the DMA engines, image data gets directed to the driver's internal scratch
>> buffer.
>> ---
>>  drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c | 3 ---
>>  1 file changed, 3 deletions(-)
>>
>> diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
>> index 2bddb4fa8a5c..2f0c610e74b9 100644
>> --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
>> +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
>> @@ -35,8 +35,6 @@
>>  #define RKISP1_SP_DEV_NAME	RKISP1_DRIVER_NAME "_selfpath"
>>  #define RKISP1_MP_DEV_NAME	RKISP1_DRIVER_NAME "_mainpath"
>>
>> -#define RKISP1_MIN_BUFFERS_NEEDED 3
>> -
>>  enum rkisp1_plane {
>>  	RKISP1_PLANE_Y	= 0,
>>  	RKISP1_PLANE_CB	= 1,
>> @@ -1563,7 +1561,6 @@ static int rkisp1_register_capture(struct rkisp1_capture *cap)
>>  	q->ops = &rkisp1_vb2_ops;
>>  	q->mem_ops = &vb2_dma_contig_memops;
>>  	q->buf_struct_size = sizeof(struct rkisp1_buffer);
>> -	q->min_queued_buffers = RKISP1_MIN_BUFFERS_NEEDED;
>>  	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
>>  	q->lock = &node->vlock;
>>  	q->dev = cap->rkisp1->dev;
>