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

[John Stultz]

On Tue, Feb 14, 2017 at 12:32 PM, Daniel Stone <daniel@xxxxxxxxxxxxx> wrote:
> 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 ...

Yea. That is not my intent at all I'm just trying to get the drm_crtc
attached to the connector that we're getting the EDID mode lines from.
I had tried going connector->encoder->crtc, but at the time this is
called, the encoder is null. So Rob suggested the for_each_crtc(), and
I guess I mistook that for being each crtc on the connector.

Thanks for pointing out this issue. From Daniel's feedback it looks
like I need to start over from scratch though, so little worry this
implementation will go much further.

thanks
-john