linux-kernel - Re: [PATCH v4] media: vimc: Add vimc-streamer for stream control

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Date:   Thu, 7 Feb 2019 19:07:20 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     "Lucas A. M. Magalhaes" <lucmaga@...il.com>,
        linux-media@...r.kernel.org
Cc:     helen.koike@...labora.com, mchehab@...nel.org,
        lkcamp@...ts.libreplanetbr.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v4] media: vimc: Add vimc-streamer for stream control

Hi Lucas,

On 1/22/19 2:05 AM, Lucas A. M. Magalhaes wrote:
> Add a linear pipeline logic for the stream control. It's created by
> walking backwards on the entity graph. When the stream starts it will
> simply loop through the pipeline calling the respective process_frame
> function of each entity.
> 
> Fixes: f2fe89061d797 ("vimc: Virtual Media Controller core, capture
> and sensor")
> Cc: stable@...r.kernel.org # for v4.20
> Signed-off-by: Lucas A. M. Magalhães <lucmaga@...il.com>
> ---
> 
> The actual approach for streaming frames on vimc uses a recursive
> logic[1]. This algorithm may cause problems as the stack usage
> increases a with the topology. For the actual topology almost 1Kb of
> stack is used if compiled with KASAN on a 64bit architecture. However
> the topology is fixed and hard-coded on vimc-core[2]. So it's a
> controlled situation if used as is.
> 
> [1]
> The stream starts on vim-sensor's thread
> https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-sensor.c#n204
> It proceeds calling successively vimc_propagate_frame
> https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-common.c#n210
> Then processes_frame on the next entity
> https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-scaler.c#n349
> https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-debayer.c#n483
> This goes until the loop ends on a vimc-capture device
> https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-capture.c#n358
> 
> [2]https://git.linuxtv.org/media_tree.git/tree/drivers/media/platform/vimc/vimc-core.c#n80
> 
> Thanks the review Helen. I've made the change you pointed out. There was really
> a bug for single entity pipelines.
> 
> Changed from v3:
> * Fix vimc_streamer_pipeline_init and vimc_streamer_pipeline_terminate for a
> single entity pipeline.
> * Remove unnecessary checks and comments.
> * Alignment and style.
> 
>  drivers/media/platform/vimc/Makefile        |   3 +-
>  drivers/media/platform/vimc/vimc-capture.c  |  18 +-
>  drivers/media/platform/vimc/vimc-common.c   |  35 ----
>  drivers/media/platform/vimc/vimc-common.h   |  15 +-
>  drivers/media/platform/vimc/vimc-debayer.c  |  26 +--
>  drivers/media/platform/vimc/vimc-scaler.c   |  28 +--
>  drivers/media/platform/vimc/vimc-sensor.c   |  56 ++----
>  drivers/media/platform/vimc/vimc-streamer.c | 188 ++++++++++++++++++++
>  drivers/media/platform/vimc/vimc-streamer.h |  38 ++++
>  9 files changed, 260 insertions(+), 147 deletions(-)
>  create mode 100644 drivers/media/platform/vimc/vimc-streamer.c
>  create mode 100644 drivers/media/platform/vimc/vimc-streamer.h
> 

<snip>

> diff --git a/drivers/media/platform/vimc/vimc-sensor.c b/drivers/media/platform/vimc/vimc-sensor.c
> index 32ca9c6172b1..93961a1e694f 100644
> --- a/drivers/media/platform/vimc/vimc-sensor.c
> +++ b/drivers/media/platform/vimc/vimc-sensor.c
> @@ -16,8 +16,6 @@
>   */
>  
>  #include <linux/component.h>
> -#include <linux/freezer.h>
> -#include <linux/kthread.h>
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/platform_device.h>
> @@ -201,38 +199,27 @@ static const struct v4l2_subdev_pad_ops vimc_sen_pad_ops = {
>  	.set_fmt		= vimc_sen_set_fmt,
>  };
>  
> -static int vimc_sen_tpg_thread(void *data)
> +static void *vimc_sen_process_frame(struct vimc_ent_device *ved,
> +				    const void *sink_frame)
>  {
> -	struct vimc_sen_device *vsen = data;
> -	unsigned int i;
> -
> -	set_freezable();
> -	set_current_state(TASK_UNINTERRUPTIBLE);
> -
> -	for (;;) {
> -		try_to_freeze();
> -		if (kthread_should_stop())
> -			break;
> -
> -		tpg_fill_plane_buffer(&vsen->tpg, 0, 0, vsen->frame);
> +	struct vimc_sen_device *vsen = container_of(ved, struct vimc_sen_device,
> +						    ved);
> +	const struct vimc_pix_map *vpix;
> +	unsigned int frame_size;
>  
> -		/* Send the frame to all source pads */
> -		for (i = 0; i < vsen->sd.entity.num_pads; i++)
> -			vimc_propagate_frame(&vsen->sd.entity.pads[i],
> -					     vsen->frame);
> +	/* Calculate the frame size */
> +	vpix = vimc_pix_map_by_code(vsen->mbus_format.code);
> +	frame_size = vsen->mbus_format.width * vpix->bpp *
> +		     vsen->mbus_format.height;

frame_size is set, but not used:

vimc-sensor.c:208:15: warning: variable 'frame_size' set but not used [-Wunused-but-set-variable]

Can you make a patch fixing this?

I'm not sure how I missed this sparse warning, weird.

>  
> -		/* 60 frames per second */
> -		schedule_timeout(HZ/60);
> -	}
> -
> -	return 0;
> +	tpg_fill_plane_buffer(&vsen->tpg, 0, 0, vsen->frame);
> +	return vsen->frame;
>  }

Regards,

	Hans