[PATCH] pipeline: simple: Increase buffer count to four

[Umang Jain]

Hi Robert,

Thank you for the patch.

On 27/09/24 2:37 am, Robert Mader wrote:
> Which is not only what many other pipeline handlers use, but also a good
> lower limit when dealing with DRM and similar APIs. Even Mesas EGL and
> Vulkan WSI implementations use for the reason outlined in mesa commit
> 992a2dbba80aba35efe83202e1013bd6143f0dba:
>> When the compositor is directly scanning out from the application's buffer it
>> may end up holding on to three buffers. These are the one that is is currently
>> scanning out from, one that has been given to DRM as the next buffer to flip
>> to, and one that has been attached and will be given to DRM as soon as the
>> previous flip completes. When we attach a fourth buffer to the compositor it
>> should replace that third buffer so we should get a release event immediately
>> after that. This patch therefore also changes the number of buffer slots to 4
>> so that we can accomodate that situation.
> Given the popularity of this buffer number the bump should be unlikely
> to cause problems. At the same time it may help with performance or
> even work around glitches.
>
> The previous number was introduced in commit
> a8964c28c80fb520ee3c7b10143371081d41405a without mentioning a specific
> reason against the change at hand.
>
> Signed-off-by: Robert Mader <robert.mader at collabora.com>

Let's add to popularity then,

Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>
> ---
>   src/libcamera/pipeline/simple/simple.cpp | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> index 81915573..78ce9232 100644
> --- a/src/libcamera/pipeline/simple/simple.cpp
> +++ b/src/libcamera/pipeline/simple/simple.cpp
> @@ -1135,7 +1135,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
>   			cfg.frameSize = format.planes[0].size;
>   		}
>   
> -		cfg.bufferCount = 3;
> +		cfg.bufferCount = 4;
>   	}
>   
>   	return status;