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Message-ID: <ff9abc0f-c934-44a9-88ba-75265699b384@samsung.com>
Date: Fri, 9 Jan 2026 09:50:09 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>, Maarten Lankhorst
<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Philippe Cornu <philippe.cornu@...com>,
benjamin.gaignard@...aro.org, Andrzej Hajda <andrzej.hajda@...el.com>, Neil
Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman
<jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, Adrien
Grassein <adrien.grassein@...il.com>, Liu Ying <victor.liu@....com>, Shawn
Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam
<festevam@...il.com>, Inki Dae <inki.dae@...sung.com>, Jagan Teki
<jagan@...rulasolutions.com>
Cc: Hui Pu <Hui.Pu@...ealthcare.com>, Thomas Petazzoni
<thomas.petazzoni@...tlin.com>, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 12/12] drm/bridge: samsung-dsim:
samsung_dsim_host_attach: convert to of_drm_find_and_get_bridge()
On 09.01.2026 08:31, Luca Ceresoli wrote:
> of_drm_find_bridge() is deprecated. Move to its replacement
> of_drm_find_and_get_bridge() which gets a bridge reference, and ensure it
> is put when done. Also switch to the drm_bridge::next_bridge pointer.
>
> This needs to handle both cases: when of_drm_find_panel() succeeds and when
> it fails.
>
> In the 'else' case (i.e. when of_drm_find_panel() fails), just switch to
> of_drm_find_and_get_bridge() to ensure the bridge is not freed while in use
> in the function tail, when it is stored in dsi->bridge.next_bridge.
>
> In the 'then' case (i.e. when of_drm_find_panel() succeeds),
> devm_drm_panel_bridge_add() already increments the refcount using devres
> which ties the bridge allocation lifetime to the device lifetime, so we
> would not need to do anything. However to have the same behaviour in both
> branches take an additional reference here, so that the bridge needs to be
> put whichever branch is taken without more complicated logic. Ensure to
> clear the bridge pointer however, to avoid calling drm_bridge_put() on an
> ERR_PTR.
>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>
> Changes in v2:
> - updated after "pointer set too late" fix inprevious patch
> - *not* add Acked-by: Maxime as the patch has changed
> ---
> drivers/gpu/drm/bridge/samsung-dsim.c | 20 +++++++++++++-------
> include/drm/bridge/samsung-dsim.h | 1 -
> 2 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> index afaa63c4d3f7..1d85e706c74b 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1828,7 +1828,7 @@ static int samsung_dsim_attach(struct drm_bridge *bridge,
> {
> struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>
> - return drm_bridge_attach(encoder, dsi->out_bridge, bridge,
> + return drm_bridge_attach(encoder, dsi->bridge.next_bridge, bridge,
> flags);
> }
>
> @@ -1886,7 +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 drm_bridge *next_bridge __free(drm_bridge_put) = NULL;
> struct device *dev = dsi->dev;
> struct device_node *np = dev->of_node;
> struct device_node *remote;
> @@ -1926,10 +1926,14 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
> panel = of_drm_find_panel(remote);
> if (!IS_ERR(panel)) {
> next_bridge = devm_drm_panel_bridge_add(dev, panel);
> - if (IS_ERR(next_bridge))
> + if (IS_ERR(next_bridge)) {
> ret = PTR_ERR(next_bridge);
> + next_bridge = NULL; // Inhibit the cleanup action on an ERR_PTR
> + } else {
> + drm_bridge_get(next_bridge);
> + }
> } else {
> - next_bridge = of_drm_find_bridge(remote);
> + next_bridge = of_drm_find_and_get_bridge(remote);
> if (!next_bridge)
> ret = -EINVAL;
> }
> @@ -1961,7 +1965,7 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
> }
>
> // The next bridge can be used by host_ops->attach
> - dsi->out_bridge = next_bridge;
> + dsi->bridge.next_bridge = drm_bridge_get(next_bridge);
>
> if (pdata->host_ops && pdata->host_ops->attach) {
> ret = pdata->host_ops->attach(dsi, device);
> @@ -1976,7 +1980,8 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
> return 0;
>
> err_release_next_bridge:
> - dsi->out_bridge = NULL;
> + drm_bridge_put(dsi->bridge.next_bridge);
> + dsi->bridge.next_bridge = NULL;
> return ret;
> }
>
> @@ -1997,7 +2002,8 @@ static int samsung_dsim_host_detach(struct mipi_dsi_host *host,
> if (pdata->host_ops && pdata->host_ops->detach)
> pdata->host_ops->detach(dsi, device);
>
> - dsi->out_bridge = NULL;
> + drm_bridge_put(dsi->bridge.next_bridge);
> + dsi->bridge.next_bridge = NULL;
>
> samsung_dsim_unregister_te_irq(dsi);
>
> diff --git a/include/drm/bridge/samsung-dsim.h b/include/drm/bridge/samsung-dsim.h
> index 31d7ed589233..03005e474704 100644
> --- a/include/drm/bridge/samsung-dsim.h
> +++ b/include/drm/bridge/samsung-dsim.h
> @@ -100,7 +100,6 @@ struct samsung_dsim_plat_data {
> struct samsung_dsim {
> struct mipi_dsi_host dsi_host;
> struct drm_bridge bridge;
> - struct drm_bridge *out_bridge;
> struct device *dev;
> struct drm_display_mode mode;
>
>
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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