drm: Move legacy device list out of drm_driver

The drm_driver structure contains a single field (legacy_dev_list) that
is modified by the DRM core, used to store a linked list of legacy DRM
devices associated with the driver. In order to make the structure
const, move the field out to a global variable. This requires locking
access to the global where the local field didn't require serialization,
but this only affects legacy drivers, and isn't in any hot path.

While at it, compile-out the legacy_dev_list field when DRM_LEGACY isn't
defined.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

1 files changed, 17 insertions, 8 deletions

diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
index 6dba4b8ce4fe..dfb138aaccba 100644
--- a/drivers/gpu/drm/drm_pci.c
+++ b/drivers/gpu/drm/drm_pci.c
@@ -24,6 +24,8 @@
 
 #include <linux/dma-mapping.h>
 #include <linux/export.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
 #include <linux/pci.h>
 #include <linux/slab.h>
 
@@ -36,6 +38,9 @@
 #include "drm_legacy.h"
 
 #ifdef CONFIG_DRM_LEGACY
+/* List of devices hanging off drivers with stealth attach. */
+static LIST_HEAD(legacy_dev_list);
+static DEFINE_MUTEX(legacy_dev_list_lock);
 
 /**
  * drm_pci_alloc - Allocate a PCI consistent memory block, for DMA.
@@ -225,10 +230,11 @@ static int drm_get_pci_dev(struct pci_dev *pdev,
 	if (ret)
 		goto err_agp;
 
-	/* No locking needed since shadow-attach is single-threaded since it may
-	 * only be called from the per-driver module init hook. */
-	if (drm_core_check_feature(dev, DRIVER_LEGACY))
-		list_add_tail(&dev->legacy_dev_list, &driver->legacy_dev_list);
+	if (drm_core_check_feature(dev, DRIVER_LEGACY)) {
+		mutex_lock(&legacy_dev_list_lock);
+		list_add_tail(&dev->legacy_dev_list, &legacy_dev_list);
+		mutex_unlock(&legacy_dev_list_lock);
+	}
 
 	return 0;
 
@@ -261,7 +267,6 @@ int drm_legacy_pci_init(struct drm_driver *driver, struct pci_driver *pdriver)
 		return -EINVAL;
 
 	/* If not using KMS, fall back to stealth mode manual scanning. */
-	INIT_LIST_HEAD(&driver->legacy_dev_list);
 	for (i = 0; pdriver->id_table[i].vendor != 0; i++) {
 		pid = &pdriver->id_table[i];
 
@@ -304,11 +309,15 @@ void drm_legacy_pci_exit(struct drm_driver *driver, struct pci_driver *pdriver)
 	if (!(driver->driver_features & DRIVER_LEGACY)) {
 		WARN_ON(1);
 	} else {
-		list_for_each_entry_safe(dev, tmp, &driver->legacy_dev_list,
+		mutex_lock(&legacy_dev_list_lock);
+		list_for_each_entry_safe(dev, tmp, &legacy_dev_list,
 					 legacy_dev_list) {
-			list_del(&dev->legacy_dev_list);
-			drm_put_dev(dev);
+			if (dev->driver == driver) {
+				list_del(&dev->legacy_dev_list);
+				drm_put_dev(dev);
+			}
 		}
+		mutex_unlock(&legacy_dev_list_lock);
 	}
 	DRM_INFO("Module unloaded\n");
 }