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bh=MXvhynDFLGl2VG/eD2ULksaHNrcYF1H4SjCXfYiNuEI=; b=OmZshL39S+98eneP+hu/yjwtRqSkN58pfmU6nEjLJ1fB2ngGo7EG8Jk3/PFROC3BjDVuiI NueKOrYh7sitc4edomP/fP7o1sBn3DSrsTiYu6W+k4QrlGhPlwF8xj3bD3uTlx0lT67tu2 /bn0hjZxKiAYwZVyV26IUo8VRvnS1dVh0ByDMj7XmzyOwRcRALa4EFkHHuAB4IqKLzLNoD G1EX8/1nTBTNzt03u/7FvmzRbV0s8/8wi7WBRWb+GOokfKTFpq3qbkzcYwImsj/XwKMR6i twMR4vtXSpPq7Y8WWF88REIwETi5bN7PfW/ChNLAJBzg+GAeHxkhA+YOXBBvoA== Date: Fri, 7 Feb 2025 09:54:01 +0100 From: Luca Ceresoli To: Dmitry Baryshkov Cc: Simona Vetter , Inki Dae , Jagan Teki , Marek Szyprowski , Catalin Marinas , Will Deacon , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Daniel Thompson , Andrzej Hajda , Jonathan Corbet , Sam Ravnborg , Boris Brezillon , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Jessica Zhang , Paul Kocialkowski , Maxime Ripard , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Thomas Zimmermann , David Airlie , =?UTF-8?Q?Herv?= =?UTF-8?Q?=C3=A9?= Codina , Thomas Petazzoni , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Paul Kocialkowski Subject: Re: [PATCH v6 11/26] drm/bridge: samsung-dsim: use devm_drm_of_get_bridge[_by_node] to find the out_bridge Message-ID: <20250207095401.42d7871d@booty> In-Reply-To: References: <20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com> <20250206-hotplug-drm-bridge-v6-11-9d6f2c9c3058@bootlin.com> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgddvkeekgecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfitefpfffkpdcuggftfghnshhusghstghrihgsvgenuceurghilhhouhhtmecufedtudenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepfffhvfevuffkjghfohfogggtgfesthejredtredtvdenucfhrhhomhepnfhutggrucevvghrvghsohhlihcuoehluhgtrgdrtggvrhgvshholhhisegsohhothhlihhnrdgtohhmqeenucggtffrrghtthgvrhhnpeeglefffefghefhtddvfeeufeeiveekgffgleekieduteekkeetvdehudekgfdvvdenucffohhmrghinhepsghoohhtlhhinhdrtghomhenucfkphepvdgrtddvmeeijedtmedvtddvtdemvggrtddumegtvgejvgemiegtgegvmeeitggtjeemleekgeejnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepvdgrtddvmeeijedtmedvtddvtdemvggrtddumegtvgejvgemiegtgegvmeeitggtjeemleekgeejpdhhvghlohepsghoohhthidpmhgrihhlfhhrohhmpehluhgtrgdrtggvrhgvshholhhisegsohhothhlihhnrdgtohhmpdhnsggprhgtphhtthhopeefjedprhgtphhtthhopegumhhithhrhidrsggrrhihshhhkhhovheslhhinhgrrhhordhorhhgpdhrtghpthhtohepshhimhhonhgrsehffhiflhhlrdgthhdprhgtphhtthhopehinhhkihdruggrvgesshgrmhhsuhhnghdrt ghomhdprhgtphhtthhopehjrghgrghnsegrmhgrrhhulhgrshholhhuthhiohhnshdrtghomhdprhgtphhtthhopehmrdhsiiihphhrohifshhkihesshgrmhhsuhhnghdrtghomhdprhgtphhtthhopegtrghtrghlihhnrdhmrghrihhnrghssegrrhhmrdgtohhmpdhrtghpthhtohepfihilhhlsehkvghrnhgvlhdrohhrghdprhgtphhtthhopehshhgrfihnghhuoheskhgvrhhnvghlrdhorhhg X-GND-Sasl: luca.ceresoli@bootlin.com On Fri, 7 Feb 2025 04:55:54 +0200 Dmitry Baryshkov wrote: > On Thu, Feb 06, 2025 at 07:14:26PM +0100, Luca Ceresoli wrote: > > In order to support panels described either via graph links or via a > > subnode (e.g. "panel@0"), this driver uses low-level deprecated functions > > to find the next bridge. The resulting logic is complex and duplicates code > > already present in the DRM bridge core. Switch to the new APIs in DRM > > bridge core that allow to do the same in a much cleaner way. > > > > Note there are two slight changes in the new logic intended to improve the > > final result: > > > > * the old code looks for a subnode with any name except "port" or "ports", > > while the new code uses the node passed as a parameter > > > > * the old code looks for a subnode first and falls back to a graph link, > > while the new code uses the reverse order because graph links are the > > recommended device tree representation now > > > > The first change makes the code more robust by avoiding the risk of using > > an unrelated node which is not describing a panel and not names "port" or > > "ports". > > > > The second change is not expected to expose regressions because, in the > > cases where both a subnode and a graph link are used to describe a panel, > > the graph link should point to the subnode itself, such as in > > arch/arm64/boot/dts/qcom/sdm850-lenovo-yoga-c630.dts > > > > As a further cleanup, use a temporary variable to assign dsi->out_bridge > > only on success. This avoids the risk of leaving a non-NULL value in > > dsi->out_bridge when samsung_dsim_host_attach() fails. > > > > Suggested-by: Dmitry Baryshkov > > Signed-off-by: Luca Ceresoli > > > > --- > > > > This patch was added in v6. > > --- > > drivers/gpu/drm/bridge/samsung-dsim.c | 55 ++++++----------------------------- > > 1 file changed, 9 insertions(+), 46 deletions(-) > > > > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c > > index f8b4fb8357659018ec0db65374ee5d05330639ae..bbd0a4f5a3f52b61bf48f10d6e8ca741bffa5e46 100644 > > --- a/drivers/gpu/drm/bridge/samsung-dsim.c > > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c > > @@ -1704,55 +1704,16 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host, > > const struct samsung_dsim_plat_data *pdata = dsi->plat_data; > > struct device *dev = dsi->dev; > > struct device_node *np = dev->of_node; > > - struct device_node *remote; > > - struct drm_panel *panel; > > + struct drm_bridge *out_bridge; > > int ret; > > > > - /* > > - * Devices can also be child nodes when we also control that device > > - * through the upstream device (ie, MIPI-DCS for a MIPI-DSI device). > > - * > > - * Lookup for a child node of the given parent that isn't either port > > - * or ports. > > - */ > > Please leave the comment in place (maybe rewrite it slightly). OK > > - for_each_available_child_of_node(np, remote) { > > - if (of_node_name_eq(remote, "port") || > > - of_node_name_eq(remote, "ports")) > > - continue; > > + out_bridge = devm_drm_of_get_bridge(dev, np, 1, 0); > > + if (IS_ERR(out_bridge) && PTR_ERR(out_bridge) != -EPROBE_DEFER) > > Can it actually return EPROBE_DEFER? It can't indeed. Dropping the second condition. > > > + out_bridge = devm_drm_of_get_bridge_by_node(dev, device->dev.of_node); > > > > - goto of_find_panel_or_bridge; > > - } > > - > > - /* > > - * of_graph_get_remote_node() produces a noisy error message if port > > - * node isn't found and the absence of the port is a legit case here, > > - * so at first we silently check whether graph presents in the > > - * device-tree node. > > - */ > > - if (!of_graph_is_present(np)) > > - return -ENODEV; > > - > > - remote = of_graph_get_remote_node(np, 1, 0); > > - > > -of_find_panel_or_bridge: > > - if (!remote) > > - return -ENODEV; > > - > > - panel = of_drm_find_panel(remote); > > - if (!IS_ERR(panel)) { > > - dsi->out_bridge = devm_drm_panel_bridge_add(dev, panel); > > - } else { > > - dsi->out_bridge = of_drm_find_bridge(remote); > > - if (!dsi->out_bridge) > > - dsi->out_bridge = ERR_PTR(-EINVAL); > > - } > > - > > - of_node_put(remote); > > - > > - if (IS_ERR(dsi->out_bridge)) { > > - ret = PTR_ERR(dsi->out_bridge); > > - DRM_DEV_ERROR(dev, "failed to find the bridge: %d\n", ret); > > - return ret; > > + if (IS_ERR(out_bridge)) { > > + DRM_DEV_ERROR(dev, "failed to find the bridge: %ld\n", PTR_ERR(out_bridge)); > > + return PTR_ERR(out_bridge); > > } > > > > DRM_DEV_INFO(dev, "Attached %s device (lanes:%d bpp:%d mode-flags:0x%lx)\n", > > @@ -1784,6 +1745,8 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host, > > dsi->format = device->format; > > dsi->mode_flags = device->mode_flags; > > > > + dsi->out_bridge = out_bridge; > > + > > Please move the assignment closer to the original place. OK. With this change it doesn't make sense to have a temporary out_bridge variable, so I'll drop it as well. Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com