Re: [PATCH v3 05/21] drm/bridge: Introduce drm_bridge_chain_get_next_bridge()

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Boris Brezillon <boris.brezillon@collabora.com>
Cc: dri-devel@lists.freedesktop.org,
	Lucas Stach <l.stach@pengutronix.de>,
	Chris Healy <cphealy@gmail.com>,
	Andrey Smirnov <andrew.smirnov@gmail.com>,
	Nikita Yushchenko <nikita.yoush@cogentembedded.com>,
	kernel@collabora.com, Daniel Vetter <daniel@ffwll.ch>,
	Inki Dae <inki.dae@samsung.com>,
	Joonyoung Shim <jy0922.shim@samsung.com>,
	Seung-Woo Kim <sw0312.kim@samsung.com>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Rob Clark <robdclark@gmail.com>,
	Andrzej Hajda <a.hajda@samsung.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org
Subject: Re: [PATCH v3 05/21] drm/bridge: Introduce drm_bridge_chain_get_next_bridge()
Date: Sun, 24 Nov 2019 16:04:30 +0200	[thread overview]
Message-ID: <20191124140430.GJ4727@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20191124115616.1491ae6d@collabora.com>

Hi Boris,

On Sun, Nov 24, 2019 at 11:56:16AM +0100, Boris Brezillon wrote:
> On Sun, 24 Nov 2019 12:33:35 +0200 Laurent Pinchart wrote:
> > On Wed, Oct 23, 2019 at 05:44:56PM +0200, Boris Brezillon wrote:
> > > And use it in drivers accessing the bridge->next field directly.
> > > This is part of our attempt to make the bridge chain a double-linked list
> > > based on the generic list helpers.
> > > 
> > > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> > > ---
> > > Changes in v3:
> > > * Inline drm_bridge_chain_get_next_bridge() (Suggested by Laurent)
> > > 
> > > Changes in v2:
> > > * Kill the last/first helpers (they're not really needed)
> > > * Drop the !bridge || !bridge->encoder test
> > > ---
> > >  drivers/gpu/drm/exynos/exynos_drm_dsi.c |  3 ++-
> > >  drivers/gpu/drm/mediatek/mtk_hdmi.c     |  6 ++++--
> > >  drivers/gpu/drm/omapdrm/omap_drv.c      |  4 ++--
> > >  drivers/gpu/drm/omapdrm/omap_encoder.c  |  3 ++-
> > >  drivers/gpu/drm/vc4/vc4_dsi.c           |  4 +++-
> > >  include/drm/drm_bridge.h                | 13 +++++++++++++
> > >  6 files changed, 26 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
> > > index 3915f50b005e..005c67894b78 100644
> > > --- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
> > > +++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
> > > @@ -1593,9 +1593,10 @@ static int exynos_dsi_host_detach(struct mipi_dsi_host *host,
> > >  				  struct mipi_dsi_device *device)
> > >  {
> > >  	struct exynos_dsi *dsi = host_to_dsi(host);
> > > -	struct drm_bridge *out_bridge = dsi->bridge.next;
> > >  	struct drm_device *drm = dsi->encoder.dev;
> > > +	struct drm_bridge *out_bridge;
> > >  
> > > +	out_bridge = drm_bridge_chain_get_next_bridge(&dsi->bridge);  
> > 
> > You may want to store this in the exynos_dsi structure in the previous
> > patch where you rework this driver.
> 
> Do we really need to store it there, since we already have a simple way
> to retrieve the next bridge in the chain?

We don't have to indeed. I thought it would be simpler, but that's
probably subjective.

> > >  	if (dsi->panel) {
> > >  		mutex_lock(&drm->mode_config.mutex);
> > >  		exynos_dsi_disable(&dsi->bridge);
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
> > > index ea68b5adccbe..cfaa5aab8876 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
> > > @@ -1238,16 +1238,18 @@ static int mtk_hdmi_conn_mode_valid(struct drm_connector *conn,
> > >  				    struct drm_display_mode *mode)
> > >  {
> > >  	struct mtk_hdmi *hdmi = hdmi_ctx_from_conn(conn);
> > > +	struct drm_bridge *next_bridge;
> > >  
> > >  	dev_dbg(hdmi->dev, "xres=%d, yres=%d, refresh=%d, intl=%d clock=%d\n",
> > >  		mode->hdisplay, mode->vdisplay, mode->vrefresh,
> > >  		!!(mode->flags & DRM_MODE_FLAG_INTERLACE), mode->clock * 1000);
> > >  
> > > -	if (hdmi->bridge.next) {
> > > +	next_bridge = drm_bridge_chain_get_next_bridge(&hdmi->bridge);
> > > +	if (next_bridge) {
> > >  		struct drm_display_mode adjusted_mode;
> > >  
> > >  		drm_mode_copy(&adjusted_mode, mode);
> > > -		if (!drm_bridge_chain_mode_fixup(hdmi->bridge.next, mode,
> > > +		if (!drm_bridge_chain_mode_fixup(next_bridge, mode,
> > >  						 &adjusted_mode))
> > >  			return MODE_BAD;
> > >  	}
> > > diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> > > index b3e22c890c51..865164fe28dc 100644
> > > --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> > > +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> > > @@ -217,8 +217,8 @@ static int omap_display_id(struct omap_dss_device *output)
> > >  	} else if (output->bridge) {
> > >  		struct drm_bridge *bridge = output->bridge;
> > >  
> > > -		while (bridge->next)
> > > -			bridge = bridge->next;
> > > +		while (drm_bridge_chain_get_next_bridge(bridge))
> > > +			bridge = drm_bridge_chain_get_next_bridge(bridge);
> > >  
> > >  		node = bridge->of_node;
> > >  	} else if (output->panel) {
> > > diff --git a/drivers/gpu/drm/omapdrm/omap_encoder.c b/drivers/gpu/drm/omapdrm/omap_encoder.c
> > > index 24bbe9f2a32e..8ca54081997e 100644
> > > --- a/drivers/gpu/drm/omapdrm/omap_encoder.c
> > > +++ b/drivers/gpu/drm/omapdrm/omap_encoder.c
> > > @@ -126,7 +126,8 @@ static void omap_encoder_mode_set(struct drm_encoder *encoder,
> > >  	for (dssdev = output; dssdev; dssdev = dssdev->next)
> > >  		omap_encoder_update_videomode_flags(&vm, dssdev->bus_flags);
> > >  
> > > -	for (bridge = output->bridge; bridge; bridge = bridge->next) {
> > > +	for (bridge = output->bridge; bridge;
> > > +	     bridge = drm_bridge_chain_get_next_bridge(bridge)) {  
> > 
> > A for_each_bridge() macro would be nice (in a separate patch). It could
> > be used in omap_drv.c above too.
> 
> It's coming later in the series (patch 8).
> 
> > >  		if (!bridge->timings)
> > >  			continue;
> > >  
> > > diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
> > > index 49f8a313e759..49c47185aff0 100644
> > > --- a/drivers/gpu/drm/vc4/vc4_dsi.c
> > > +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
> > > @@ -1644,8 +1644,10 @@ static void vc4_dsi_unbind(struct device *dev, struct device *master,
> > >  	struct drm_device *drm = dev_get_drvdata(master);
> > >  	struct vc4_dev *vc4 = to_vc4_dev(drm);
> > >  	struct vc4_dsi *dsi = dev_get_drvdata(dev);
> > > +	struct drm_bridge *bridge;
> > >  
> > > -	if (dsi->bridge.next)
> > > +	bridge = drm_bridge_chain_get_next_bridge(&dsi->bridge);
> > > +	if (bridge)
> > >  		pm_runtime_disable(dev);
> > >  
> > >  	vc4_dsi_encoder_destroy(dsi->encoder);
> > > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > > index 726435baf4ad..8aeba83fcf31 100644
> > > --- a/include/drm/drm_bridge.h
> > > +++ b/include/drm/drm_bridge.h
> > > @@ -409,6 +409,19 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np);
> > >  int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> > >  		      struct drm_bridge *previous);
> > >  
> > > +/**
> > > + * drm_bridge_chain_get_next_bridge() - Get the next bridge in the chain
> > > + * @bridge: bridge object
> > > + *
> > > + * RETURNS:
> > > + * the next bridge in the chain, or NULL if @bridge is the last.  
> > 
> > Maybe "the next bridge in the chain after @bridge, ..." ?
> 
> Agreed.
> 
> > > + */
> > > +static inline struct drm_bridge *
> > > +drm_bridge_chain_get_next_bridge(struct drm_bridge *bridge)  
> > 
> > Technically speaking this doesn't operate on a chain but on a bridge, so
> > I'd name is drm_bridge_get_next_bridge(). I will not insist to the way
> > of nacking the series for this, so with the rename, but also without,
> 
> You're absolutely right, I'll rename the function as suggested.
> 
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > 
> > > +{
> > > +	return bridge->next;
> > > +}
> > > +
> > >  bool drm_bridge_chain_mode_fixup(struct drm_bridge *bridge,
> > >  				 const struct drm_display_mode *mode,
> > >  				 struct drm_display_mode *adjusted_mode);  

-- 
Regards,

Laurent Pinchart