[RFC v2 4/8] drm/fb-helper: Ensure driver module is pinned in fb_open()

Noralf Trønnes
2018-01-03T22:21:06Z

If struct fb_ops is defined in a library like cma, fb_open() and fbcon
takes a ref on the library instead of the driver module. Use
fb_ops.fb_open/fb_release to ensure that the driver module is pinned.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
drivers/gpu/drm/drm_fb_helper.c | 40 ++++++++++++++++++++++++++++++++++++++++
include/drm/drm_fb_helper.h | 13 +++++++++++++
2 files changed, 53 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 035784ddd133..2c6adf1d80c2 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1207,6 +1207,46 @@ void drm_fb_helper_cfb_imageblit(struct fb_info *info,
}
EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);

+/**
+ * drm_fb_helper_fb_open - implementation for &fb_ops.fb_open
+ * @info: fbdev registered by the helper
+ * @user: 1=userspace, 0=fbcon
+ *
+ * If &fb_ops is wrapped in a library, pin the driver module.
+ */
+int drm_fb_helper_fb_open(struct fb_info *info, int user)
+{
+ struct drm_fb_helper *fb_helper = info->par;
+ struct drm_device *dev = fb_helper->dev;
+
+ if (info->fbops->owner != dev->driver->fops->owner) {
+ if (!try_module_get(dev->driver->fops->owner))
+ return -ENODEV;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_fb_helper_fb_open);
+
+/**
+ * drm_fb_helper_fb_release - implementation for &fb_ops.fb_release
+ * @info: fbdev registered by the helper
+ * @user: 1=userspace, 0=fbcon
+ *
+ * If &fb_ops is wrapped in a library, unpin the driver module.
+ */
+int drm_fb_helper_fb_release(struct fb_info *info, int user)
+{
+ struct drm_fb_helper *fb_helper = info->par;
+ struct drm_device *dev = fb_helper->dev;
+
+ if (info->fbops->owner != dev->driver->fops->owner)
+ module_put(dev->driver->fops->owner);
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_fb_helper_fb_release);
+
/**
* drm_fb_helper_set_suspend - wrapper around fb_set_suspend
* @fb_helper: driver-allocated fbdev helper, can be NULL
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index b069433e7fc1..a593f01ff69e 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -297,6 +297,9 @@ void drm_fb_helper_cfb_copyarea(struct fb_info *info,
void drm_fb_helper_cfb_imageblit(struct fb_info *info,
const struct fb_image *image);

+int drm_fb_helper_fb_open(struct fb_info *info, int user);
+int drm_fb_helper_fb_release(struct fb_info *info, int user);
+
void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper, bool suspend);
void drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper,
bool suspend);
@@ -473,6 +476,16 @@ static inline void drm_fb_helper_cfb_imageblit(struct fb_info *info,
{
}

+static inline int drm_fb_helper_fb_open(struct fb_info *info, int user)
+{
+ return -ENODEV;
+}
+
+static inline int drm_fb_helper_fb_release(struct fb_info *info, int user)
+{
+ return -ENODEV;
+}
+
static inline void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper,
bool suspend)
{
--
2.14.2