drm/omap: Fix possible NULL dereference

smatch reports:

drivers/gpu/drm/omapdrm/dss/base.c:176 omapdss_device_disconnect() error: we previously assumed 'src' could be null (see line 169)

This code is mostly from a time when omapdrm had its own display device
model. I can't honestly remember the details, and I don't think it's
worth digging in deeply into that for a legacy driver.

However, it looks like we only call omapdss_device_disconnect() and
omapdss_device_connect() with NULL as the src parameter. We can thus
drop the src parameter from both functions, and fix the smatch warning.

I don't think omapdss_device_disconnect() ever gets NULL for the dst
parameter (if it did, we'd crash soon after returning from the
function), but I have kept the !dst check, just in case, but I added a
WARN_ON() there.

Also, if the dst parameter can be NULL, we can't always get the struct
dss_device pointer from dst->dss (which is only used for a debug print).
To make sure we can't hit that issue, do it similarly to the
omapdss_device_connect() function: add 'struct dss_device *dss' as the
first parameter, so that we always have it regardless of the dst.

Fixes: 79107f274b2f ("drm/omap: Add support for drm_bridge")
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240806-omapdrm-misc-fixes-v1-1-15d31aea0831@ideasonboard.com

diff --git a/drivers/gpu/drm/omapdrm/dss/base.c b/drivers/gpu/drm/omapdrm/dss/base.c
index 5f8002f6bb7a59bc153f99c291380e1eb25c31b7..a4ac113e16904b829596257b644742a29b5f8ec8 100644 (file)
--- a/drivers/gpu/drm/omapdrm/dss/base.c
+++ b/drivers/gpu/drm/omapdrm/dss/base.c
@@ -139,21 +139,13 @@ static bool omapdss_device_is_connected(struct omap_dss_device *dssdev)
 }
 
 int omapdss_device_connect(struct dss_device *dss,
-                          struct omap_dss_device *src,
                           struct omap_dss_device *dst)
 {
-       dev_dbg(&dss->pdev->dev, "connect(%s, %s)\n",
-               src ? dev_name(src->dev) : "NULL",
+       dev_dbg(&dss->pdev->dev, "connect(%s)\n",
                dst ? dev_name(dst->dev) : "NULL");
 
-       if (!dst) {
-               /*
-                * The destination is NULL when the source is connected to a
-                * bridge instead of a DSS device. Stop here, we will attach
-                * the bridge later when we will have a DRM encoder.
-                */
-               return src && src->bridge ? 0 : -EINVAL;
-       }
+       if (!dst)
+               return -EINVAL;
 
        if (omapdss_device_is_connected(dst))
                return -EBUSY;
@@ -163,19 +155,14 @@ int omapdss_device_connect(struct dss_device *dss,
        return 0;
 }
 
-void omapdss_device_disconnect(struct omap_dss_device *src,
+void omapdss_device_disconnect(struct dss_device *dss,
                               struct omap_dss_device *dst)
 {
-       struct dss_device *dss = src ? src->dss : dst->dss;
-
-       dev_dbg(&dss->pdev->dev, "disconnect(%s, %s)\n",
-               src ? dev_name(src->dev) : "NULL",
+       dev_dbg(&dss->pdev->dev, "disconnect(%s)\n",
                dst ? dev_name(dst->dev) : "NULL");
 
-       if (!dst) {
-               WARN_ON(!src->bridge);
+       if (WARN_ON(!dst))
                return;
-       }
 
        if (!dst->id && !omapdss_device_is_connected(dst)) {
                WARN_ON(1);

diff --git a/drivers/gpu/drm/omapdrm/dss/omapdss.h b/drivers/gpu/drm/omapdrm/dss/omapdss.h
index 040d5a3e33d6806e5cbf879abfb749a24d8e0ab0..4c22c09c93d5239507ba309a0a0d5fad9c586957 100644 (file)
--- a/drivers/gpu/drm/omapdrm/dss/omapdss.h
+++ b/drivers/gpu/drm/omapdrm/dss/omapdss.h
@@ -242,9 +242,8 @@ struct omap_dss_device *omapdss_device_get(struct omap_dss_device *dssdev);
 void omapdss_device_put(struct omap_dss_device *dssdev);
 struct omap_dss_device *omapdss_find_device_by_node(struct device_node *node);
 int omapdss_device_connect(struct dss_device *dss,
-                          struct omap_dss_device *src,
                           struct omap_dss_device *dst);
-void omapdss_device_disconnect(struct omap_dss_device *src,
+void omapdss_device_disconnect(struct dss_device *dss,
                               struct omap_dss_device *dst);
 
 int omap_dss_get_num_overlay_managers(void);

diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
index d3eac4817d76870d8fda064271a47a0be9815e1f..a982378aa14119e063b4d678fb96e389751621ab 100644 (file)
--- a/drivers/gpu/drm/omapdrm/omap_drv.c
+++ b/drivers/gpu/drm/omapdrm/omap_drv.c
@@ -307,7 +307,7 @@ static void omap_disconnect_pipelines(struct drm_device *ddev)
        for (i = 0; i < priv->num_pipes; i++) {
                struct omap_drm_pipeline *pipe = &priv->pipes[i];
 
-               omapdss_device_disconnect(NULL, pipe->output);
+               omapdss_device_disconnect(priv->dss, pipe->output);
 
                omapdss_device_put(pipe->output);
                pipe->output = NULL;
@@ -325,7 +325,7 @@ static int omap_connect_pipelines(struct drm_device *ddev)
        int r;
 
        for_each_dss_output(output) {
-               r = omapdss_device_connect(priv->dss, NULL, output);
+               r = omapdss_device_connect(priv->dss, output);
                if (r == -EPROBE_DEFER) {
                        omapdss_device_put(output);
                        return r;