Subject: Re: [PATCH] drm: add fb max width/height fields to drm_mode_config

From: Ville Syrjälä <[email-masked]>
Date: Mon, 30 Sep 2019 13:39:31 +0300

On Fri, Sep 27, 2019 at 06:28:51PM -0700, Jeykumar Sankaran wrote:
> The mode_config max width/height values determine the maximum
> resolution the pixel reader can handle.

Not according to the docs I "fixed" a while ago.

> But the same values are
> used to restrict the size of the framebuffer creation. Hardware's
> with scaling blocks can operate on framebuffers larger/smaller than
> that of the pixel reader resolutions by scaling them down/up before
> rendering.
> 
> This changes adds a separate framebuffer max width/height fields
> in drm_mode_config to allow vendors to set if they are different
> than that of the default max resolution values.

If you're going to change the meaning of the old values you need
to fix the drivers too.

Personally I don't see too much point in this since you most likely
want to validate all the other timings as well, and so likely need
some kind of mode_valid implementation anyway. Hence to validate
modes there's not much benefit of having global min/max values.

> 
> Vendors setting these fields should fix their mode_set paths too
> by filtering and validating the modes against the appropriate max
> fields in their mode_valid() implementations.
> 
> Signed-off-by: Neil Armstrong <[email-masked]>
> Signed-off-by: Jeykumar Sankaran <[email-masked]>
> ---
>  drivers/gpu/drm/drm_framebuffer.c | 15 +++++++++++----
>  include/drm/drm_mode_config.h     |  3 +++
>  2 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index 5756431..2083168 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -300,14 +300,21 @@ struct drm_framebuffer *
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> -	if ((config->min_width > r->width) || (r->width > config->max_width)) {
> +	if ((config->min_width > r->width) ||
> +	    (!config->max_fb_width && r->width > config->max_width) ||
> +	    (config->max_fb_width && r->width > config->max_fb_width)) {
>  		DRM_DEBUG_KMS("bad framebuffer width %d, should be >= %d && <= %d\n",
> -			  r->width, config->min_width, config->max_width);
> +			r->width, config->min_width, config->max_fb_width ?
> +			config->max_fb_width : config->max_width);
>  		return ERR_PTR(-EINVAL);
>  	}
> -	if ((config->min_height > r->height) || (r->height > config->max_height)) {
> +
> +	if ((config->min_height > r->height) ||
> +	    (!config->max_fb_height && r->height > config->max_height) ||
> +	    (config->max_fb_height && r->height > config->max_fb_height)) {
>  		DRM_DEBUG_KMS("bad framebuffer height %d, should be >= %d && <= %d\n",
> -			  r->height, config->min_height, config->max_height);
> +			r->height, config->min_height, config->max_fb_width ?
> +			config->max_fb_height : config->max_height);
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 3bcbe30..c6394ed 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -339,6 +339,8 @@ struct drm_mode_config_funcs {
>   * @min_height: minimum fb pixel height on this device
>   * @max_width: maximum fb pixel width on this device
>   * @max_height: maximum fb pixel height on this device
> + * @max_fb_width: maximum fb buffer width if differs from max_width
> + * @max_fb_height: maximum fb buffer height if differs from  max_height
>   * @funcs: core driver provided mode setting functions
>   * @fb_base: base address of the framebuffer
>   * @poll_enabled: track polling support for this device
> @@ -523,6 +525,7 @@ struct drm_mode_config {
>  
>  	int min_width, min_height;
>  	int max_width, max_height;
> +	int max_fb_width, max_fb_height;
>  	const struct drm_mode_config_funcs *funcs;
>  	resource_size_t fb_base;
>  
> -- 
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> a Linux Foundation Collaborative Project
> 
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-- 
Ville Syrjälä
Intel

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