Re: [PATCH v3 2/2] media: v4l: xilinx: Add Xilinx MIPI CSI-2 Rx Subsystem

[Luca Ceresoli]

Hi,

thanks for the quick reply.

On 11/02/19 13:43, Vishal Sagar wrote:
>>> +static int xcsi2rxss_start_stream(struct xcsi2rxss_state *state)
>>> +{
>>> +     struct xcsi2rxss_core *core = &state->core;
>>> +     int ret = 0;
>>> +
>>> +     xcsi2rxss_enable(core);
>>> +
>>> +     ret = xcsi2rxss_reset(core);
>>> +     if (ret < 0) {
>>> +             state->streaming = false;
>>> +             return ret;
>>> +     }
>>> +
>>> +     xcsi2rxss_intr_enable(core);
>>> +     state->streaming = true;
>>
>> Shouldn't you propagate s_stream to the upstream subdev here calling
>> v4l2_subdev_call(..., ..., s_stream, 1)?
>>
> 
> This is done by the xvip_pipeline_start_stop() in xilinx-dma.c for Xilinx Video pipeline.

Indeed it does, however other CSI2 RX drivers do propagate s_stream in
their own s_stream. Not strictly related to this driver, but what's the
logic for having these two different behaviors?

Also xvip_pipeline_start_stop() only follows the graph through
entity->pads[0], so it looks like it cannot handle entities with
multiple sink pads. How would it be able to handle e.g. the AXI4-Stream
Switch [0], which has 2+ sink pads?

[0]
https://www.xilinx.com/support/documentation/ip_documentation/axis_infrastructure_ip_suite/v1_1/pg085-axi4stream-infrastructure.pdf
(page 16).

-- 
Luca