linux-kernel - Re: [PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

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Message-ID: <2efaff3aeb732a2d3bf2ca184063d5b923aa5002.camel@redhat.com>
Date:   Mon, 17 Sep 2018 13:58:12 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     dri-devel@...ts.freedesktop.org, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/probe_helper: Don't bother probing when connectors
 are forced off

On Mon, 2018-09-17 at 20:55 +0300, Ville Syrjälä wrote:
> On Mon, Sep 17, 2018 at 01:43:44PM -0400, Lyude Paul wrote:
> > Userspace asked them to be forced off, so why would we care about what a
> > probe tells us?
> 
> I believe there should be force checks in the callers already.
> Or are we missing some?

JFYI, this is to fix "DDC responded but no EDID" errors from nouveau, which
presumably come from the fact that having a connector forced off disables
reading it's EDID. It's possible we are missing something in
nouveau_connector_detect(), but I'm confused as to why we would want to call
->probe() at all in the first place
> 
> > 
> > Signed-off-by: Lyude Paul <lyude@...hat.com>
> > ---
> >  drivers/gpu/drm/drm_probe_helper.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_probe_helper.c
> > b/drivers/gpu/drm/drm_probe_helper.c
> > index a1bb157bfdfa..56d2b5dd1f58 100644
> > --- a/drivers/gpu/drm/drm_probe_helper.c
> > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > @@ -269,7 +269,9 @@ drm_helper_probe_detect_ctx(struct drm_connector
> > *connector, bool force)
> >  retry:
> >  	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex,
> > &ctx);
> >  	if (!ret) {
> > -		if (funcs->detect_ctx)
> > +		if (connector->force == DRM_FORCE_OFF)
> > +			ret = connector_status_disconnected;
> 
> connector->force is protected by mode_config.mutex IIRC.
> 
> > +		else if (funcs->detect_ctx)
> >  			ret = funcs->detect_ctx(connector, &ctx, force);
> >  		else if (connector->funcs->detect)
> >  			ret = connector->funcs->detect(connector, force);
> > @@ -317,6 +319,9 @@ drm_helper_probe_detect(struct drm_connector *connector,
> >  	if (ret)
> >  		return ret;
> >  
> > +	if (connector->force == DRM_FORCE_OFF)
> > +		return connector_status_disconnected;
> > +
> >  	if (funcs->detect_ctx)
> >  		return funcs->detect_ctx(connector, ctx, force);
> >  	else if (connector->funcs->detect)
> > -- 
> > 2.17.1
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
>

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