drm: make sysfs device always available for minors

For each minor we allocate a sysfs device as minor->kdev. Currently, this
is allocated and registered in drm_minor_register(). This makes it
impossible to add sysfs-attributes to the device before it is registered.
Therefore, they are not added atomically, nor can we move device_add()
*after* ->load() is called.

This patch makes minor->kdev available early, but only adds the device
during minor-registration. Note that the registration is still called
before ->load() as debugfs needs to be split, too. This will be fixed in
follow-ups.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>

diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 8b24db51116eb1893828614886c77d46b1d12cd6..09c6bfb86a66c6f12eefcfeb928a88e5b88be643 100644 (file)
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -281,9 +281,19 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 
        minor->index = r;
 
+       minor->kdev = drm_sysfs_minor_alloc(minor);
+       if (IS_ERR(minor->kdev)) {
+               r = PTR_ERR(minor->kdev);
+               goto err_index;
+       }
+
        *drm_minor_get_slot(dev, type) = minor;
        return 0;
 
+err_index:
+       spin_lock_irqsave(&drm_minor_lock, flags);
+       idr_remove(&drm_minors_idr, minor->index);
+       spin_unlock_irqrestore(&drm_minor_lock, flags);
 err_free:
        kfree(minor);
        return r;
@@ -300,6 +310,7 @@ static void drm_minor_free(struct drm_device *dev, unsigned int type)
                return;
 
        drm_mode_group_destroy(&minor->mode_group);
+       put_device(minor->kdev);
 
        spin_lock_irqsave(&drm_minor_lock, flags);
        idr_remove(&drm_minors_idr, minor->index);
@@ -327,11 +338,9 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type)
                return ret;
        }
 
-       ret = drm_sysfs_device_add(minor);
-       if (ret) {
-               DRM_ERROR("DRM: Error sysfs_device_add.\n");
+       ret = device_add(minor->kdev);
+       if (ret)
                goto err_debugfs;
-       }
 
        /* replace NULL with @minor so lookups will succeed from now on */
        spin_lock_irqsave(&drm_minor_lock, flags);
@@ -352,7 +361,7 @@ static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
        unsigned long flags;
 
        minor = *drm_minor_get_slot(dev, type);
-       if (!minor || !minor->kdev)
+       if (!minor || !device_is_registered(minor->kdev))
                return;
 
        /* replace @minor with NULL so lookups will fail from now on */
@@ -360,8 +369,9 @@ static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
        idr_replace(&drm_minors_idr, NULL, minor->index);
        spin_unlock_irqrestore(&drm_minor_lock, flags);
 
+       device_del(minor->kdev);
+       dev_set_drvdata(minor->kdev, NULL); /* safety belt */
        drm_debugfs_cleanup(minor);
-       drm_sysfs_device_remove(minor);
 }
 
 /**

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 7827dad8fcf4fbf1e08fd76be6798277b992436d..ab1a5f6dde8afd40a58987d4faa2f5f2f54828cb 100644 (file)
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -493,71 +493,55 @@ static void drm_sysfs_release(struct device *dev)
 }
 
 /**
- * drm_sysfs_device_add - adds a class device to sysfs for a character driver
- * @dev: DRM device to be added
- * @head: DRM head in question
+ * drm_sysfs_minor_alloc() - Allocate sysfs device for given minor
+ * @minor: minor to allocate sysfs device for
  *
- * Add a DRM device to the DRM's device model class.  We use @dev's PCI device
- * as the parent for the Linux device, and make sure it has a file containing
- * the driver we're using (for userspace compatibility).
+ * This allocates a new sysfs device for @minor and returns it. The device is
+ * not registered nor linked. The caller has to use device_add() and
+ * device_del() to register and unregister it.
+ *
+ * Note that dev_get_drvdata() on the new device will return the minor.
+ * However, the device does not hold a ref-count to the minor nor to the
+ * underlying drm_device. This is unproblematic as long as you access the
+ * private data only in sysfs callbacks. device_del() disables those
+ * synchronously, so they cannot be called after you cleanup a minor.
  */
-int drm_sysfs_device_add(struct drm_minor *minor)
+struct device *drm_sysfs_minor_alloc(struct drm_minor *minor)
 {
-       char *minor_str;
+       const char *minor_str;
+       struct device *kdev;
        int r;
 
        if (minor->type == DRM_MINOR_CONTROL)
                minor_str = "controlD%d";
-        else if (minor->type == DRM_MINOR_RENDER)
-                minor_str = "renderD%d";
-        else
-                minor_str = "card%d";
-
-       minor->kdev = kzalloc(sizeof(*minor->kdev), GFP_KERNEL);
-       if (!minor->kdev) {
-               r = -ENOMEM;
-               goto error;
-       }
-
-       device_initialize(minor->kdev);
-       minor->kdev->devt = MKDEV(DRM_MAJOR, minor->index);
-       minor->kdev->class = drm_class;
-       minor->kdev->type = &drm_sysfs_device_minor;
-       minor->kdev->parent = minor->dev->dev;
-       minor->kdev->release = drm_sysfs_release;
-       dev_set_drvdata(minor->kdev, minor);
-
-       r = dev_set_name(minor->kdev, minor_str, minor->index);
+       else if (minor->type == DRM_MINOR_RENDER)
+               minor_str = "renderD%d";
+       else
+               minor_str = "card%d";
+
+       kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
+       if (!kdev)
+               return ERR_PTR(-ENOMEM);
+
+       device_initialize(kdev);
+       kdev->devt = MKDEV(DRM_MAJOR, minor->index);
+       kdev->class = drm_class;
+       kdev->type = &drm_sysfs_device_minor;
+       kdev->parent = minor->dev->dev;
+       kdev->release = drm_sysfs_release;
+       dev_set_drvdata(kdev, minor);
+
+       r = dev_set_name(kdev, minor_str, minor->index);
        if (r < 0)
-               goto error;
-
-       r = device_add(minor->kdev);
-       if (r < 0)
-               goto error;
-
-       return 0;
+               goto err_free;
 
-error:
-       DRM_ERROR("device create failed %d\n", r);
-       put_device(minor->kdev);
-       return r;
-}
+       return kdev;
 
-/**
- * drm_sysfs_device_remove - remove DRM device
- * @dev: DRM device to remove
- *
- * This call unregisters and cleans up a class device that was created with a
- * call to drm_sysfs_device_add()
- */
-void drm_sysfs_device_remove(struct drm_minor *minor)
-{
-       if (minor->kdev)
-               device_unregister(minor->kdev);
-       minor->kdev = NULL;
+err_free:
+       put_device(kdev);
+       return ERR_PTR(r);
 }
 
-
 /**
  * drm_class_device_register - Register a struct device in the drm class.
  *

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index c480b448ce65af439abc0d5de0122549751418fe..458385ec15f3626bd4ddba9e11919024e1c9df6d 100644 (file)
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1502,9 +1502,8 @@ extern int drm_pci_set_unique(struct drm_device *dev,
 struct drm_sysfs_class;
 extern struct class *drm_sysfs_create(struct module *owner, char *name);
 extern void drm_sysfs_destroy(void);
-extern int drm_sysfs_device_add(struct drm_minor *minor);
+extern struct device *drm_sysfs_minor_alloc(struct drm_minor *minor);
 extern void drm_sysfs_hotplug_event(struct drm_device *dev);
-extern void drm_sysfs_device_remove(struct drm_minor *minor);
 extern int drm_sysfs_connector_add(struct drm_connector *connector);
 extern void drm_sysfs_connector_remove(struct drm_connector *connector);