drm/connector: add mutex to protect ELD from concurrent access

The connector->eld is accessed by the .get_eld() callback. This access
can collide with the drm_edid_to_eld() updating the data at the same
time. Add drm_connector.eld_mutex to protect the data from concurrenct
access. Individual drivers are not updated (to reduce possible issues
while applying the patch), maintainers are to find a best suitable way
to lock that mutex while accessing the ELD data.

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241206-drm-connector-eld-mutex-v2-1-c9bce1ee8bea@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index fc35f47e2849ed6786d6223ac9c69e1c359fc648..bbdaaf7022b62d84594a29f1b60144920903a99a 100644 (file)
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -277,6 +277,7 @@ static int __drm_connector_init(struct drm_device *dev,
        INIT_LIST_HEAD(&connector->probed_modes);
        INIT_LIST_HEAD(&connector->modes);
        mutex_init(&connector->mutex);
+       mutex_init(&connector->eld_mutex);
        mutex_init(&connector->edid_override_mutex);
        mutex_init(&connector->hdmi.infoframes.lock);
        connector->edid_blob_ptr = NULL;

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 855beafb76ffbecf5c08d58e2f54bfb76f30b930..13bc4c290b17d556d654b7cdd8c48c24a32aba9c 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5605,7 +5605,9 @@ EXPORT_SYMBOL(drm_edid_get_monitor_name);
 
 static void clear_eld(struct drm_connector *connector)
 {
+       mutex_lock(&connector->eld_mutex);
        memset(connector->eld, 0, sizeof(connector->eld));
+       mutex_unlock(&connector->eld_mutex);
 
        connector->latency_present[0] = false;
        connector->latency_present[1] = false;
@@ -5657,6 +5659,8 @@ static void drm_edid_to_eld(struct drm_connector *connector,
        if (!drm_edid)
                return;
 
+       mutex_lock(&connector->eld_mutex);
+
        mnl = get_monitor_name(drm_edid, &eld[DRM_ELD_MONITOR_NAME_STRING]);
        drm_dbg_kms(connector->dev, "[CONNECTOR:%d:%s] ELD monitor %s\n",
                    connector->base.id, connector->name,
@@ -5717,6 +5721,8 @@ static void drm_edid_to_eld(struct drm_connector *connector,
        drm_dbg_kms(connector->dev, "[CONNECTOR:%d:%s] ELD size %d, SAD count %d\n",
                    connector->base.id, connector->name,
                    drm_eld_size(eld), total_sad_count);
+
+       mutex_unlock(&connector->eld_mutex);
 }
 
 static int _drm_edid_to_sad(const struct drm_edid *drm_edid,

diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index e3fa43291f449d70f3b92a00985336c4f2237bc6..1e2b25e204cb523d61d30f5409faa059bf2b86eb 100644 (file)
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -2001,8 +2001,11 @@ struct drm_connector {
        struct drm_encoder *encoder;
 
 #define MAX_ELD_BYTES  128
-       /** @eld: EDID-like data, if present */
+       /** @eld: EDID-like data, if present, protected by @eld_mutex */
        uint8_t eld[MAX_ELD_BYTES];
+       /** @eld_mutex: protection for concurrenct access to @eld */
+       struct mutex eld_mutex;
+
        /** @latency_present: AV delay info from ELD, if found */
        bool latency_present[2];
        /**