linux-kernel - Re: [PATCH v5 2/6] drm/bridge: Add a devm

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Date:   Fri, 04 Aug 2017 17:57:03 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Eric Anholt <eric@...olt.net>, Daniel Vetter <daniel@...ll.ch>,
        linux-kernel@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH v5 2/6] drm/bridge: Add a devm_ allocator for panel bridge.

Now CC'ing Daniel with his correct address :-/ I'll blame auto-completion in 
my e-mail client. Sorry for the noise.

On Friday 04 Aug 2017 16:46:24 Laurent Pinchart wrote:
> Hi Eric,
> 
> (CC'ing Daniel)
> 
> Thank you for the patch.
> 
> On Tuesday 18 Jul 2017 14:05:06 Eric Anholt wrote:
> > This will let drivers reduce the error cleanup they need, in
> > particular the "is_panel_bridge" flag.
> > 
> > v2: Slight cleanup of remove function by Andrzej
> 
> I just want to point out that, in the context of Daniel's work on
> hot-unplug, 90% of the devm_* allocations are wrong and will get in the
> way. All DRM core objects that are accessible one way or another from
> userspace will need to be properly reference-counted and freed only when
> the last reference disappears, which could be well after the corresponding
> device is removed. I believe this could be one such objects :-/
> 
> > Signed-off-by: Eric Anholt <eric@...olt.net>
> > Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> > ---
> > 
> >  drivers/gpu/drm/bridge/panel.c | 30 ++++++++++++++++++++++++++++++
> >  include/drm/drm_bridge.h       |  3 +++
> >  2 files changed, 33 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/bridge/panel.c
> > b/drivers/gpu/drm/bridge/panel.c index 685c1a480201..292ee92a9c97 100644
> > --- a/drivers/gpu/drm/bridge/panel.c
> > +++ b/drivers/gpu/drm/bridge/panel.c
> > @@ -195,3 +195,33 @@ void drm_panel_bridge_remove(struct drm_bridge
> > *bridge) devm_kfree(panel_bridge->panel->dev, bridge);
> > 
> >  }
> >  EXPORT_SYMBOL(drm_panel_bridge_remove);
> > 
> > +
> > +static void devm_drm_panel_bridge_release(struct device *dev, void *res)
> > +{
> > +	struct drm_bridge **bridge = res;
> > +
> > +	drm_panel_bridge_remove(*bridge);
> > +}
> > +
> > +struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
> > +					     struct drm_panel *panel,
> > +					     u32 connector_type)
> > +{
> > +	struct drm_bridge **ptr, *bridge;
> > +
> > +	ptr = devres_alloc(devm_drm_panel_bridge_release, sizeof(*ptr),
> > +			   GFP_KERNEL);
> > +	if (!ptr)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	bridge = drm_panel_bridge_add(panel, connector_type);
> > +	if (!IS_ERR(bridge)) {
> > +		*ptr = bridge;
> > +		devres_add(dev, ptr);
> > +	} else {
> > +		devres_free(ptr);
> > +	}
> > +
> > +	return bridge;
> > +}
> > +EXPORT_SYMBOL(devm_drm_panel_bridge_add);
> > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > index 1dc94d5392e2..6522d4cbc9d9 100644
> > --- a/include/drm/drm_bridge.h
> > +++ b/include/drm/drm_bridge.h
> > @@ -268,6 +268,9 @@ void drm_bridge_enable(struct drm_bridge *bridge);
> > 
> >  struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
> >  
> >  					u32 connector_type);
> >  
> >  void drm_panel_bridge_remove(struct drm_bridge *bridge);
> > 
> > +struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
> > +					     struct drm_panel *panel,
> > +					     u32 connector_type);
> > 
> >  #endif
> >  
> >  #endif

-- 
Regards,

Laurent Pinchart