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

[Mark yao <mark.yao@xxxxxxxxxxxxxx>]

On 2017年02月15日 04:32, Daniel Stone 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 ...

John, I have same requirement, also want to valid mode with crtc,
here is my patch[0], use encoder->possible_crtcs to limit the crtc valid, may be can solved the low-res and high-res problem.

[0]: https://patchwork.kernel.org/patch/9555945

    /*
     * ensure all drm display mode can work, if someone want support more
     * resolutions, please limit the possible_crtc, only connect to
     * needed crtc.
     */
    drm_for_each_crtc(crtc, connector->dev) {
        [...]
        if (!(encoder->possible_crtcs & drm_crtc_mask(crtc)))

Cheers,
Daniel
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-- 
Ｍark Yao

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