linux-kernel - Re: [PATCH v2 1/2] media: tpg: Add function to return colors' order of test image

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Message-ID: <50f015af-3c09-3871-78a4-026baca56345@ideasonboard.com>
Date:   Mon, 15 Jun 2020 12:42:56 +0100
From:   Kieran Bingham <kieran.bingham@...asonboard.com>
To:     Kaaira Gupta <kgupta@...iitr.ac.in>,
        Helen Koike <helen.koike@...labora.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        hverkuil@...all.nl
Subject: Re: [PATCH v2 1/2] media: tpg: Add function to return colors' order
 of test image

Hi Kaaira,

On 14/06/2020 21:02, Kaaira Gupta wrote:
> Currently there is no method to know the correct order of the colors for
> a test image generated by tpg. Write a function that returns a string of
> colors' order given a tpg. It returns a NULL pointer in case of test
> patterns which do not have a well defined colors' order. Hence add a
> NULL check for text in tpg_gen_text().
> 
> Signed-off-by: Kaaira Gupta <kgupta@...iitr.ac.in>
> ---
>  drivers/media/common/v4l2-tpg/v4l2-tpg-core.c | 32 +++++++++++++++++--
>  include/media/tpg/v4l2-tpg.h                  |  1 +
>  2 files changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
> index 50f1e0b28b25..c8257e860c6e 100644
> --- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
> +++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
> @@ -1959,12 +1959,14 @@ void tpg_gen_text(const struct tpg_data *tpg, u8 *basep[TPG_MAX_PLANES][2],
>  	unsigned step = V4L2_FIELD_HAS_T_OR_B(tpg->field) ? 2 : 1;
>  	unsigned div = step;
>  	unsigned first = 0;
> -	unsigned len = strlen(text);
> +	unsigned len;
>  	unsigned p;
>  
> -	if (font8x16 == NULL || basep == NULL)
> +	if (font8x16 == NULL || basep == NULL || text == NULL)
>  		return;
>  
> +	len = strlen(text);
> +
>  	/* Checks if it is possible to show string */
>  	if (y + 16 >= tpg->compose.height || x + 8 >= tpg->compose.width)
>  		return;
> @@ -2006,6 +2008,32 @@ void tpg_gen_text(const struct tpg_data *tpg, u8 *basep[TPG_MAX_PLANES][2],
>  }
>  EXPORT_SYMBOL_GPL(tpg_gen_text);
>  
> +char *tpg_g_color_order(const struct tpg_data *tpg)
> +{
> +	switch (tpg->pattern) {
> +	case TPG_PAT_75_COLORBAR:
> +		return "Left to right: white, yellow, cyan, green, magenta, red, blue, black";
> +	case TPG_PAT_100_COLORBAR:
> +		return "Left to right: white, yellow, cyan, green, magenta, red, blue, black";
> +	case TPG_PAT_CSC_COLORBAR:
> +		return "Left to right: white, yellow, cyan, green, magenta, red, blue, black";

Those three options return identical strings.

In C you can 'fallthrough' on case statements like this:

> switch (tpg->pattern) {
> case TPG_PAT_75_COLORBAR:
> case TPG_PAT_100_COLORBAR:
> case TPG_PAT_CSC_COLORBAR:
>	return "Left to right: white, yellow, cyan, green, magenta, red, blue, black";

So all three of those options will go to the same return statement.


> +	case TPG_PAT_100_HCOLORBAR:
> +		return "Top to bottom: white, yellow, cyan, green, magenta, red, blue, black";

It would be nice to be able to factor out the common color sequence from
those (two remaining) strings too, as only the direction changes.

But perhaps it's a pain to have to do a string join in this call,
especially given it's static string data otherwise, but that's also a
good reason not to duplicate unnecessarily (as it wastes space in memory).

With those fixed,

Reviewed-by: Kieran Bingham <kieran.bingham@...asonboard.com>



> +	case TPG_PAT_BLACK:
> +		return "Black";
> +	case TPG_PAT_WHITE:
> +		return "White";
> +	case TPG_PAT_RED:
> +		return "Red";
> +	case TPG_PAT_GREEN:
> +		return "Green";
> +	case TPG_PAT_BLUE:
> +		return "Blue";
> +	default:
> +		return NULL;
> +	}
> +}
> +
>  void tpg_update_mv_step(struct tpg_data *tpg)
>  {
>  	int factor = tpg->mv_hor_mode > TPG_MOVE_NONE ? -1 : 1;
> diff --git a/include/media/tpg/v4l2-tpg.h b/include/media/tpg/v4l2-tpg.h
> index eb191e85d363..4f79cac87b85 100644
> --- a/include/media/tpg/v4l2-tpg.h
> +++ b/include/media/tpg/v4l2-tpg.h
> @@ -252,6 +252,7 @@ void tpg_fillbuffer(struct tpg_data *tpg, v4l2_std_id std,
>  bool tpg_s_fourcc(struct tpg_data *tpg, u32 fourcc);
>  void tpg_s_crop_compose(struct tpg_data *tpg, const struct v4l2_rect *crop,
>  		const struct v4l2_rect *compose);
> +char *tpg_g_color_order(const struct tpg_data *tpg);
>  
>  static inline void tpg_s_pattern(struct tpg_data *tpg, enum tpg_pattern pattern)
>  {
> 

-- 
Regards
--
Kieran