media: bcm2835-codec: Limit video callbacks

commit  56c8fad9d9ffdbdd79932bcc7e73b3965c7a725e from
https://github.com/raspberrypi/linux.git rpi-5.15.y

Limit the number of allowed video callbacks. This helps with limiting
the size of the coded input FIFO which in turn helps to control latency.
Choose -5 as the magic number as it translates to DPB+5 buffers which
has been proven to be a good number in the past.

Ideally coded buffers would not be returned to the user until they
had been decoded into the DPB or been discarded as bad, but that grade
of control is unavailable to us.

Signed-off-by: John Cox <[email protected]>
Signed-off-by: Meng Li <[email protected]>

Author: jc-kynesim

drivers/staging/vc04_services/bcm2835-codec/bcm2835-v4l2-codec.c

@@ -2510,6 +2510,14 @@ static int bcm2835_codec_create_component(struct bcm2835_codec_ctx *ctx)
 					      MMAL_PARAMETER_VIDEO_STOP_ON_PAR_COLOUR_CHANGE,
 					      &enable,
 					      sizeof(enable));
+
+		enable = (unsigned int)-5;
+		vchiq_mmal_port_parameter_set(dev->instance,
+					      &ctx->component->control,
+					      MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS,
+					      &enable,
+					      sizeof(enable));
+
 	} else if (dev->role == DEINTERLACE) {
 		/* Select the default deinterlace algorithm. */
 		int half_framerate = 0;