[PATCH] drm: Print erroneous hscale/vscale on failure

[Ville Syrjälä]

On Wed, Sep 05, 2018 at 04:46:01PM -0400, Sean Paul wrote:
> From: Sean Paul <seanpaul at chromium.org>
> 
> I ran across this last week when I was trying to get this function to
> work. It's useful to have the scale values in the log upon failure.
> 
> Signed-off-by: Sean Paul <seanpaul at chromium.org>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 2c23a48482da..1725546d5105 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -758,7 +758,8 @@ int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
>  	hscale = drm_rect_calc_hscale(src, dst, min_scale, max_scale);
>  	vscale = drm_rect_calc_vscale(src, dst, min_scale, max_scale);
>  	if (hscale < 0 || vscale < 0) {
> -		DRM_DEBUG_KMS("Invalid scaling of plane\n");
> +		DRM_DEBUG_KMS("Invalid scaling of plane (%d/%d)\n",
> +			      hscale, vscale);

I think it's just going to be -ERANGE for at least one of them.
So not quite sure what extra benefit we get from this. What
might be more helpful is printing the actual computed scale
factor and the min/max.

>  		drm_rect_debug_print("src: ", &plane_state->src, true);
>  		drm_rect_debug_print("dst: ", &plane_state->dst, false);
>  		return -ERANGE;
> -- 
> Sean Paul, Software Engineer, Google / Chromium OS
> 
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-- 
Ville Syrjälä
Intel