Hi,

On 19/09/2019 05:30, jsanka@codeaurora.org wrote:

Hello All,

I bumped into the below check [1] enforced in drm_framebuffer creation which checks the requested framebuffer width/height parameters against the drm mode config width/height limits. As I understand, drm_mode_config: min/max width/height indicate the upper and lower bounds of the display panel (drm_connector) resolutions the DRM device can support. But the pixel processing pipeline can apply cropping/scaling transformations on much larger input framebuffers and flip the buffers within the display resolution. Such configurations are very common and the final resolution will be still within drm_mode_config bounds. So I believe the checks should be relaxed / removed from the drm_framebuffer creation api’s.

If my understanding is incorrect, could somehow explain the motivation behind having these checks here?

I already reported this a few months ago, here is the log of the discussion : https://patchwork.kernel.org/patch/10625707/

TL;DR it should be removed but these checks should be moved to control max screen size in atomic_commit paths.

I planned to fix this, but haven't found time yet...

Neil

Thanks and Regards,

Jeykumar S.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/driv...

*struct*drm_framebuffer *

*drm_internal_framebuffer_create*(*struct*drm_device *dev,

*const**struct*drm_mode_fb_cmd2 *r,

*struct*drm_file *file_priv)

{

/* snip */

*if*((config->min_width > r->width) || (r->width > config->max_width)) {

DRM_DEBUG_KMS("bad framebuffer width %d, should be >= %d && <= %d\n",

r->width, config->min_width, config->max_width);

*return*ERR_PTR(-EINVAL);

}

*if*((config->min_height > r->height) || (r->height > config->max_height)) {

DRM_DEBUG_KMS("bad framebuffer height %d, should be >= %d && <= %d\n",

r->height, config->min_height, config->max_height);

*return*ERR_PTR(-EINVAL);

}

/* snip */

}

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