Re: [RFC][PATCH 1/2] drm/probe-helper: Add mode_valid check to drm_crtc_helper_funcs

[Daniel Stone]

Hi John,

On 14 February 2017 at 19:25, John Stultz <john.stultz@xxxxxxxxxx> wrote:
> +static enum drm_mode_status
> +drm_connector_check_crtc_modes(struct drm_connector *connector,
> +                              struct drm_display_mode *mode)
> +{
> +       struct drm_device *dev = connector->dev;
> +       const struct drm_crtc_helper_funcs *crtc_funcs;
> +       struct drm_crtc *c;
> +
> +       if (mode->status != MODE_OK)
> +               return mode->status;
> +
> +       /* Check all the crtcs on a connector to make sure the mode is valid */
> +       drm_for_each_crtc(c, dev) {
> +               crtc_funcs = c->helper_private;
> +               if (crtc_funcs && crtc_funcs->mode_valid)
> +                       mode->status = crtc_funcs->mode_valid(c, mode);
> +               if (mode->status != MODE_OK)
> +                       break;
> +       }
> +       return mode->status;
> +}

Hm, that's unfortunate: it limits the mode list for every connector,
to those which are supported by every single CRTC. So if you have one
CRTC serving low-res LVDS, and another serving higher-res HDMI,
suddenly you can't get bigger modes on HDMI. The idea seems sound
enough, but a little more nuance might be good ...

Cheers,
Daniel