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b=nOZjhSGv1YGPvHr2Zl/9q3doGkRmNn1kOdXWDHSasXIgoxcOPbcE/uu36cwS6kJlt GXbiCODlqjU4qXU1e8GXDz4jUwwkcLE+QU8RUt22ePOWK5UYAfHxKHiY0rz2X/2D/s Ys9Uro5lSKsJQtJjfFYLRTuVsbRSIKJF+NOvKqog= Received: from eusmtip2.samsung.com (unknown [203.254.199.222]) by eucas1p1.samsung.com (KnoxPortal) with ESMTPA id 20260108092625eucas1p11ea9ec4b425f965756e20ce868d978f5~It0rPVBLS1910219102eucas1p1U; Thu, 8 Jan 2026 09:26:25 +0000 (GMT) Received: from [106.210.134.192] (unknown [106.210.134.192]) by eusmtip2.samsung.com (KnoxPortal) with ESMTPA id 20260108092623eusmtip237d8c787e2565d8b21a713976d5c8430~It0pFdj_i2540125401eusmtip2B; Thu, 8 Jan 2026 09:26:23 +0000 (GMT) Message-ID: Date: Thu, 8 Jan 2026 10:26:22 +0100 MIME-Version: 1.0 User-Agent: Betterbird (Windows) Subject: Re: [PATCH 10/12] drm/bridge: samsung-dsim: samsung_dsim_host_attach: use a temporary variable for the next bridge To: Luca Ceresoli , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Philippe Cornu , benjamin.gaignard@linaro.org, Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Adrien Grassein , Liu Ying , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Inki Dae , Jagan Teki Cc: Hui Pu , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org Content-Language: en-US From: Marek Szyprowski In-Reply-To: <20260107-drm-bridge-alloc-getput-drm_of_find_bridge-2-v1-10-283d7bba061a@bootlin.com> Content-Transfer-Encoding: 7bit X-CMS-MailID: 20260108092625eucas1p11ea9ec4b425f965756e20ce868d978f5 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20260107131416eucas1p22557f62e9d6498e5fdda4e6280cfe793 X-EPHeader: CA X-CMS-RootMailID: 20260107131416eucas1p22557f62e9d6498e5fdda4e6280cfe793 References: <20260107-drm-bridge-alloc-getput-drm_of_find_bridge-2-v1-0-283d7bba061a@bootlin.com> <20260107-drm-bridge-alloc-getput-drm_of_find_bridge-2-v1-10-283d7bba061a@bootlin.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260108_012632_832259_61DE78C4 X-CRM114-Status: GOOD ( 23.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 07.01.2026 14:13, Luca Ceresoli wrote: > In preparation to handle refcounting of the out_bridge, we need to ensure > the out_bridge pointer contains either a valid bridge pointer or NULL, not > an ERR_PTR. Otherwise calls such as drm_bridge_get/put() would try to > redeference an ERR_PTR. > > As a preliminary cleanup, add a temporary local 'next_bridge' pointer and > only copy it in dsi->out_bridge when returning successfully. > > Signed-off-by: Luca Ceresoli > --- > drivers/gpu/drm/bridge/samsung-dsim.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c > index eabc4c32f6ab..b3003aa49dc3 100644 > --- a/drivers/gpu/drm/bridge/samsung-dsim.c > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c > @@ -1886,6 +1886,7 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host, > { > struct samsung_dsim *dsi = host_to_dsi(host); > const struct samsung_dsim_plat_data *pdata = dsi->plat_data; > + struct drm_bridge *next_bridge; > struct device *dev = dsi->dev; > struct device_node *np = dev->of_node; > struct device_node *remote; > @@ -1924,17 +1925,17 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host, > > panel = of_drm_find_panel(remote); > if (!IS_ERR(panel)) { > - dsi->out_bridge = devm_drm_panel_bridge_add(dev, panel); > + next_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); > + next_bridge = of_drm_find_bridge(remote); > + if (!next_bridge) > + next_bridge = ERR_PTR(-EINVAL); > } > > of_node_put(remote); > > - if (IS_ERR(dsi->out_bridge)) { > - ret = PTR_ERR(dsi->out_bridge); > + if (IS_ERR(next_bridge)) { > + ret = PTR_ERR(next_bridge); > DRM_DEV_ERROR(dev, "failed to find the bridge: %d\n", ret); > return ret; > } > @@ -1967,6 +1968,7 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host, > dsi->lanes = device->lanes; > dsi->format = device->format; > dsi->mode_flags = device->mode_flags; > + dsi->out_bridge = next_bridge; > This assignment is too late, dsi->out_bridge is used (indirectly, by samsung_dsim_attach() called from drm_bridge_attach()) by ret = pdata->host_ops->attach(dsi, device); a few lines before this assignment, so the following fix has to be added: diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c index b3003aa49dc3..f88aa8ab2879 100644 --- a/drivers/gpu/drm/bridge/samsung-dsim.c +++ b/drivers/gpu/drm/bridge/samsung-dsim.c @@ -1959,6 +1959,7 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host, return ret; } + dsi->out_bridge = next_bridge; if (pdata->host_ops && pdata->host_ops->attach) { ret = pdata->host_ops->attach(dsi, device); if (ret) @@ -1968,7 +1969,6 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host, dsi->lanes = device->lanes; dsi->format = device->format; dsi->mode_flags = device->mode_flags; - dsi->out_bridge = next_bridge; return 0; } Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland