drm/panel: Make of_drm_find_panel() return an ERR_PTR() instead of NULL

Right now, the DRM panel logic returns NULL when a panel pointing to
the passed OF node is not present in the list of registered panels.

Most drivers interpret this NULL value as -EPROBE_DEFER, but we are
about to modify the semantic of of_drm_find_panel() and let the
framework return -ENODEV when the device node we're pointing to has
a status property that is not equal to "okay" or "ok".

Let's first patch the of_drm_find_panel() implementation to return
ERR_PTR(-EPROBE_DEFER) instead of NULL and patch all callers to replace
the '!panel' check by an 'IS_ERR(panel)' one.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180509130042.9435-2-boris.brezillon@bootlin.com

18 files changed, 43 insertions, 25 deletions

diff --git a/drivers/gpu/drm/bridge/cdns-dsi.c b/drivers/gpu/drm/bridge/cdns-dsi.c
index f2d43f24acfb..ce9496d13986 100644
--- a/drivers/gpu/drm/bridge/cdns-dsi.c
+++ b/drivers/gpu/drm/bridge/cdns-dsi.c
@@ -1152,7 +1152,7 @@ static int cdns_dsi_attach(struct mipi_dsi_host *host,
                 np = of_node_get(dev->dev.of_node);
 
         panel = of_drm_find_panel(np);
-        if (panel) {
+        if (!IS_ERR(panel)) {
                 bridge = drm_panel_bridge_add(panel, DRM_MODE_CONNECTOR_DSI);
         } else {
                 bridge = of_drm_find_bridge(dev->dev.of_node);
diff --git a/drivers/gpu/drm/bridge/lvds-encoder.c b/drivers/gpu/drm/bridge/lvds-encoder.c
index 75b0d3f6e4de..f56c92f7af7c 100644
--- a/drivers/gpu/drm/bridge/lvds-encoder.c
+++ b/drivers/gpu/drm/bridge/lvds-encoder.c
@@ -68,9 +68,9 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 
         panel = of_drm_find_panel(panel_node);
         of_node_put(panel_node);
-        if (!panel) {
+        if (IS_ERR(panel)) {
                 dev_dbg(&pdev->dev, "panel not found, deferring probe\n");
-                return -EPROBE_DEFER;
+                return PTR_ERR(panel);
         }
 
         lvds_encoder->panel_bridge =
diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index 3b8c7a6a5720..1f4a16772583 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -241,8 +241,10 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 
         if (panel) {
                 *panel = of_drm_find_panel(remote);
-                if (*panel)
+                if (!IS_ERR(*panel))
                         ret = 0;
+                else
+                        *panel = NULL;
         }
 
         /* No panel found yet, check for a bridge next. */
diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index 965530a6f4cd..7e5530a04846 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -151,7 +151,9 @@ EXPORT_SYMBOL(drm_panel_detach);
  * tree node. If a matching panel is found, return a pointer to it.
  *
  * Return: A pointer to the panel registered for the specified device tree
- * node or NULL if no panel matching the device tree node can be found.
+ * node or an ERR_PTR() if no panel matching the device tree node can be found.
+ * The only error that can be reported is -EPROBE_DEFER, meaning that the panel
+ * device has not been probed yet, and the caller should retry later.
  */
 struct drm_panel *of_drm_find_panel(const struct device_node *np)
 {
@@ -167,7 +169,7 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np)
         }
 
         mutex_unlock(&panel_lock);
-        return NULL;
+        return ERR_PTR(-EPROBE_DEFER);
 }
 EXPORT_SYMBOL(of_drm_find_panel);
 #endif
diff --git a/drivers/gpu/drm/exynos/exynos_dp.c b/drivers/gpu/drm/exynos/exynos_dp.c
index 86330f396784..af7ab1ceb50f 100644
--- a/drivers/gpu/drm/exynos/exynos_dp.c
+++ b/drivers/gpu/drm/exynos/exynos_dp.c
@@ -232,9 +232,11 @@ static int exynos_dp_probe(struct platform_device *pdev)
         np = of_parse_phandle(dev->of_node, "panel", 0);
         if (np) {
                 dp->plat_data.panel = of_drm_find_panel(np);
+
                 of_node_put(np);
-                if (!dp->plat_data.panel)
-                        return -EPROBE_DEFER;
+                if (IS_ERR(dp->plat_data.panel))
+                        return PTR_ERR(dp->plat_data.panel);
+
                 goto out;
         }
 
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dpi.c b/drivers/gpu/drm/exynos/exynos_drm_dpi.c
index 66945e0dc57f..5887e8522b70 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dpi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dpi.c
@@ -240,8 +240,8 @@ struct drm_encoder *exynos_dpi_probe(struct device *dev)
 
         if (ctx->panel_node) {
                 ctx->panel = of_drm_find_panel(ctx->panel_node);
-                if (!ctx->panel)
-                        return ERR_PTR(-EPROBE_DEFER);
+                if (IS_ERR(ctx->panel))
+                        return ERR_CAST(ctx->panel);
         }
 
         return &ctx->encoder;
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
index 6d29777884f9..809e1e0447df 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
@@ -1519,6 +1519,9 @@ static int exynos_dsi_host_attach(struct mipi_dsi_host *host,
         dsi->format = device->format;
         dsi->mode_flags = device->mode_flags;
         dsi->panel = of_drm_find_panel(device->dev.of_node);
+        if (IS_ERR(dsi->panel))
+                dsi->panel = NULL;
+
         if (dsi->panel) {
                 drm_panel_attach(dsi->panel, &dsi->connector);
                 dsi->connector.status = connector_status_connected;
diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c
index c54806d08dd7..681e2a07d03b 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c
@@ -148,8 +148,9 @@ int fsl_dcu_create_outputs(struct fsl_dcu_drm_device *fsl_dev)
         if (panel_node) {
                 fsl_dev->connector.panel = of_drm_find_panel(panel_node);
                 of_node_put(panel_node);
-                if (!fsl_dev->connector.panel)
-                        return -EPROBE_DEFER;
+                if (IS_ERR(fsl_dev->connector.panel))
+                        return PTR_ERR(fsl_dev->connector.panel);
+
                 return fsl_dcu_attach_panel(fsl_dev, fsl_dev->connector.panel);
         }
 
diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c
index 4a645926edb7..2bfb39082f54 100644
--- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c
+++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c
@@ -341,7 +341,7 @@ static void mdp4_lcdc_encoder_disable(struct drm_encoder *encoder)
         mdp4_write(mdp4_kms, REG_MDP4_LCDC_ENABLE, 0);
 
         panel = of_drm_find_panel(mdp4_lcdc_encoder->panel_node);
-        if (panel) {
+        if (!IS_ERR(panel)) {
                 drm_panel_disable(panel);
                 drm_panel_unprepare(panel);
         }
@@ -410,7 +410,7 @@ static void mdp4_lcdc_encoder_enable(struct drm_encoder *encoder)
                 dev_err(dev->dev, "failed to enable lcdc_clk: %d\n", ret);
 
         panel = of_drm_find_panel(mdp4_lcdc_encoder->panel_node);
-        if (panel) {
+        if (!IS_ERR(panel)) {
                 drm_panel_prepare(panel);
                 drm_panel_enable(panel);
         }
diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
index e3b1c86b7aae..32fba5664b0e 100644
--- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
+++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
@@ -34,9 +34,12 @@ static enum drm_connector_status mdp4_lvds_connector_detect(
         struct mdp4_lvds_connector *mdp4_lvds_connector =
                         to_mdp4_lvds_connector(connector);
 
-        if (!mdp4_lvds_connector->panel)
+        if (!mdp4_lvds_connector->panel) {
                 mdp4_lvds_connector->panel =
                         of_drm_find_panel(mdp4_lvds_connector->panel_node);
+                if (IS_ERR(mdp4_lvds_connector->panel))
+                        mdp4_lvds_connector->panel = NULL;
+        }
 
         return mdp4_lvds_connector->panel ?
                         connector_status_connected :
diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 2f1a2780658a..29841f440111 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1898,7 +1898,7 @@ int msm_dsi_host_register(struct mipi_dsi_host *host, bool check_defer)
                  * output
                  */
                 if (check_defer && msm_host->device_node) {
-                        if (!of_drm_find_panel(msm_host->device_node))
+                        if (IS_ERR(of_drm_find_panel(msm_host->device_node)))
                                 if (!of_drm_find_bridge(msm_host->device_node))
                                         return -EPROBE_DEFER;
                 }
diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
index 155ad840f3c5..5d8e391e75f4 100644
--- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
+++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
@@ -434,8 +434,8 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
                         ret = -EPROBE_DEFER;
         } else {
                 lvds->panel = of_drm_find_panel(remote);
-                if (!lvds->panel)
-                        ret = -EPROBE_DEFER;
+                if (IS_ERR(lvds->panel))
+                        ret = PTR_ERR(lvds->panel);
         }
 
 done:
diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
index d53d5a09547f..01642aaf6127 100644
--- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
@@ -595,7 +595,7 @@ static int dw_mipi_dsi_host_attach(struct mipi_dsi_host *host,
         dsi->format = device->format;
         dsi->mode_flags = device->mode_flags;
         dsi->panel = of_drm_find_panel(device->dev.of_node);
-        if (dsi->panel)
+        if (!IS_ERR(dsi->panel))
                 return drm_panel_attach(dsi->panel, &dsi->connector);
 
         return -EINVAL;
diff --git a/drivers/gpu/drm/sti/sti_dvo.c b/drivers/gpu/drm/sti/sti_dvo.c
index a5979cd25cc7..030da55a8d30 100644
--- a/drivers/gpu/drm/sti/sti_dvo.c
+++ b/drivers/gpu/drm/sti/sti_dvo.c
@@ -387,7 +387,9 @@ sti_dvo_connector_detect(struct drm_connector *connector, bool force)
 
         if (!dvo->panel) {
                 dvo->panel = of_drm_find_panel(dvo->panel_node);
-                if (dvo->panel)
+                if (IS_ERR(dvo->panel))
+                        dvo->panel = NULL;
+                else
                         drm_panel_attach(dvo->panel, connector);
         }
 
diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index da9814f94d00..2b40d1f6aee8 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -833,8 +833,8 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
 
         dsi->device = device;
         dsi->panel = of_drm_find_panel(device->dev.of_node);
-        if (!dsi->panel)
-                return -EINVAL;
+        if (IS_ERR(dsi->panel))
+                return PTR_ERR(dsi->panel);
 
         dev_info(host->dev, "Attached device %s\n", device->name);
 
diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c
index 87c5d89bc9ba..ad88ec230329 100644
--- a/drivers/gpu/drm/tegra/dsi.c
+++ b/drivers/gpu/drm/tegra/dsi.c
@@ -1411,6 +1411,9 @@ static int tegra_dsi_host_attach(struct mipi_dsi_host *host,
                 struct tegra_output *output = &dsi->output;
 
                 output->panel = of_drm_find_panel(device->dev.of_node);
+                if (IS_ERR(output->panel))
+                        output->panel = NULL;
+
                 if (output->panel && output->connector.dev) {
                         drm_panel_attach(output->panel, &output->connector);
                         drm_helper_hpd_irq_event(output->connector.dev);
diff --git a/drivers/gpu/drm/tegra/output.c b/drivers/gpu/drm/tegra/output.c
index ffe34bd0bb9d..0c0936511bb4 100644
--- a/drivers/gpu/drm/tegra/output.c
+++ b/drivers/gpu/drm/tegra/output.c
@@ -110,8 +110,8 @@ int tegra_output_probe(struct tegra_output *output)
         panel = of_parse_phandle(output->of_node, "nvidia,panel", 0);
         if (panel) {
                 output->panel = of_drm_find_panel(panel);
-                if (!output->panel)
-                        return -EPROBE_DEFER;
+                if (IS_ERR(output->panel))
+                        return PTR_ERR(output->panel);
 
                 of_node_put(panel);
         }
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 26a1b5fd8796..582a0ec0aa70 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -200,7 +200,7 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np);
 #else
 static inline struct drm_panel *of_drm_find_panel(const struct device_node *np)
 {
-        return NULL;
+        return ERR_PTR(-ENODEV);
 }
 #endif