If there's a DRM master, return -EBUSY.
Block userspace from becoming master by taking the master lock while
the client is setting the mode.
Suggested-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
---
drivers/gpu/drm/drm_auth.c | 33 +++++++++++++++++++++++++++++++++
drivers/gpu/drm/drm_client.c | 34 +++++++++++++++++++++++++++++-----
drivers/gpu/drm/drm_fb_helper.c | 8 ++++----
drivers/gpu/drm/drm_internal.h | 2 ++
include/drm/drm_client.h | 4 ++--
5 files changed, 70 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index d9c0f7573905..d656d0d93da3 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -366,3 +366,36 @@ void drm_master_put(struct drm_master **master)
*master = NULL;
}
EXPORT_SYMBOL(drm_master_put);
+
+/**
+ * drm_master_block - Block DRM master operations
+ * @dev: DRM device
+ *
+ * This function checks if there is a master on @dev. If there is no master it
+ * blocks anyone from becoming master. In-kernel clients can use this to know
+ * when they can act as master. Use drm_master_unblock() to unblock.
+ *
+ * Returns:
+ * True if there is no master, false otherwise.
+ */
+bool drm_master_block(struct drm_device *dev)
+{
+ mutex_lock(&dev->master_mutex);
+ if (dev->master) {
+ mutex_unlock(&dev->master_mutex);
+ return false;
+ }
+
+ return true;
+}
+
+/**
+ * drm_master_unblock - Unblock DRM master operations
+ * @dev: DRM device
+ *
+ * Unblock and allow userspace to become master.
+ */
+void drm_master_unblock(struct drm_device *dev)
+{
+ mutex_unlock(&dev->master_mutex);
+}
diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index 27818a467b09..764c556630b8 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -18,6 +18,8 @@
#include <drm/drm_device.h>
#include <drm/drm_modes.h>
+#include "drm_internal.h"
+
struct drm_client_display_offset {
int x, y;
};
@@ -313,18 +315,30 @@ static int drm_client_display_restore_legacy(struct drm_client_display *display)
/**
* drm_client_display_restore() - Restore client display
* @display: Client display
+ * @force: If true, restore even if there's a DRM master
*
* Restore client display using the current modeset configuration.
*
* Return:
* Zero on succes or negative error code on failure.
*/
-int drm_client_display_restore(struct drm_client_display *display)
+int drm_client_display_restore(struct drm_client_display *display, bool force)
{
- if (drm_drv_uses_atomic_modeset(display->dev))
- return drm_client_display_restore_atomic(display, true);
+ struct drm_device *dev = display->dev;
+ int ret;
+
+ if (!force && !drm_master_block(dev))
+ return -EBUSY;
+
+ if (drm_drv_uses_atomic_modeset(dev))
+ ret = drm_client_display_restore_atomic(display, true);
else
- return drm_client_display_restore_legacy(display);
+ ret = drm_client_display_restore_legacy(display);
+
+ if (!force)
+ drm_master_unblock(dev);
+
+ return ret;
}
EXPORT_SYMBOL(drm_client_display_restore);
@@ -354,13 +368,23 @@ static void drm_client_display_dpms_legacy(struct drm_client_display *display, i
* drm_client_display_dpms() - Set display DPMS mode
* @display: Client display
* @mode: DPMS mode
+ *
+ * Returns:
+ * Zero on success, -EBUSY if there's a DRM master.
*/
-void drm_client_display_dpms(struct drm_client_display *display, int mode)
+int drm_client_display_dpms(struct drm_client_display *display, int mode)
{
+ if (!drm_master_block(display->dev))
+ return -EBUSY;
+
if (drm_drv_uses_atomic_modeset(display->dev))
drm_client_display_restore_atomic(display, mode == DRM_MODE_DPMS_ON);
else
drm_client_display_dpms_legacy(display, mode);
+
+ drm_master_unblock(display->dev);
+
+ return 0;
}
EXPORT_SYMBOL(drm_client_display_dpms);
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 01d8840930a3..98e5bc92c9f2 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -181,7 +181,7 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
return 0;
mutex_lock(&fb_helper->lock);
- ret = drm_client_display_restore(fb_helper->display);
+ ret = drm_client_display_restore(fb_helper->display, false);
do_delayed = fb_helper->delayed_hotplug;
if (do_delayed)
@@ -243,7 +243,7 @@ static bool drm_fb_helper_force_kernel_mode(void)
continue;
mutex_lock(&helper->lock);
- ret = drm_client_display_restore(helper->display);
+ ret = drm_client_display_restore(helper->display, true);
if (ret)
error = true;
mutex_unlock(&helper->lock);
@@ -1254,7 +1254,7 @@ static int pan_display_atomic(struct fb_var_screeninfo *var,
pan_set(fb_helper, var->xoffset, var->yoffset);
- ret = drm_client_display_restore(fb_helper->display);
+ ret = drm_client_display_restore(fb_helper->display, false);
if (!ret) {
info->var.xoffset = var->xoffset;
info->var.yoffset = var->yoffset;
@@ -1423,7 +1423,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
/* First time: disable all crtc's.. */
if (!fb_helper->deferred_setup && !READ_ONCE(fb_helper->dev->master))
- drm_client_display_restore(fb_helper->display);
+ drm_client_display_restore(fb_helper->display, false);
return -EAGAIN;
}
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index 3f5d7706bcc9..f38dcaf139d7 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -92,6 +92,8 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_priv);
int drm_master_open(struct drm_file *file_priv);
void drm_master_release(struct drm_file *file_priv);
+bool drm_master_block(struct drm_device *dev);
+void drm_master_unblock(struct drm_device *dev);
/* drm_sysfs.c */
extern struct class *drm_class;
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
index 27d2a46cd94a..3befd879a0b0 100644
--- a/include/drm/drm_client.h
+++ b/include/drm/drm_client.h
@@ -46,8 +46,8 @@ drm_client_display_find_modeset(struct drm_client_display *display, struct drm_c
bool drm_client_display_panel_rotation(struct drm_connector *connector,
struct drm_plane *plane,
unsigned int *rotation);
-int drm_client_display_restore(struct drm_client_display *display);
-void drm_client_display_dpms(struct drm_client_display *display, int mode);
+int drm_client_display_restore(struct drm_client_display *display, bool force);
+int drm_client_display_dpms(struct drm_client_display *display, int mode);
struct drm_client_display *
drm_client_find_display(struct drm_device *dev, unsigned int width, unsigned int height);
--
2.15.1
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