drm: add core support for unplugging a device (v2)

Two parts to this, one is simple unplug from sysfs for the device node.

The second adds an unplugged state, if we have device opens, we
just set the unplugged state and return, if we have no device
opens we drop the drm device.

If after a lastclose we discover we are unplugged we then
drop the drm device.

v2: use an atomic for unplugged and wrap it for users,
add checks on open + mmap + ioctl entry points.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_drv.c

@@ -390,6 +390,10 @@ long drm_ioctl(struct file *filp,
 	unsigned int usize, asize;
 
 	dev = file_priv->minor->dev;
+
+	if (drm_device_is_unplugged(dev))
+		return -ENODEV;
+
 	atomic_inc(&dev->ioctl_count);
 	atomic_inc(&dev->counts[_DRM_STAT_IOCTLS]);
 	++file_priv->ioctl_count;

drivers/gpu/drm/drm_fops.c

@@ -133,6 +133,9 @@ int drm_open(struct inode *inode, struct file *filp)
 	if (!(dev = minor->dev))
 		return -ENODEV;
 
+	if (drm_device_is_unplugged(dev))
+		return -ENODEV;
+
 	retcode = drm_open_helper(inode, filp, dev);
 	if (!retcode) {
 		atomic_inc(&dev->counts[_DRM_STAT_OPENS]);
@@ -181,6 +184,9 @@ int drm_stub_open(struct inode *inode, struct file *filp)
 	if (!(dev = minor->dev))
 		goto out;
 
+	if (drm_device_is_unplugged(dev))
+		goto out;
+
 	old_fops = filp->f_op;
 	filp->f_op = fops_get(dev->driver->fops);
 	if (filp->f_op == NULL) {
@@ -579,6 +585,8 @@ int drm_release(struct inode *inode, struct file *filp)
 			retcode = -EBUSY;
 		} else
 			retcode = drm_lastclose(dev);
+		if (drm_device_is_unplugged(dev))
+			drm_put_dev(dev);
 	}
 	mutex_unlock(&drm_global_mutex);
 

drivers/gpu/drm/drm_gem.c

@@ -661,6 +661,9 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 	struct drm_hash_item *hash;
 	int ret = 0;
 
+	if (drm_device_is_unplugged(dev))
+		return -ENODEV;
+
 	mutex_lock(&dev->struct_mutex);
 
 	if (drm_ht_find_item(&mm->offset_hash, vma->vm_pgoff, &hash)) {

drivers/gpu/drm/drm_stub.c

@@ -429,6 +429,11 @@ int drm_put_minor(struct drm_minor **minor_p)
 	return 0;
 }
 
+static void drm_unplug_minor(struct drm_minor *minor)
+{
+	drm_sysfs_device_remove(minor);
+}
+
 /**
  * Called via drm_exit() at module unload time or when pci device is
  * unplugged.
@@ -492,3 +497,21 @@ void drm_put_dev(struct drm_device *dev)
 	kfree(dev);
 }
 EXPORT_SYMBOL(drm_put_dev);
+
+void drm_unplug_dev(struct drm_device *dev)
+{
+	/* for a USB device */
+	if (drm_core_check_feature(dev, DRIVER_MODESET))
+		drm_unplug_minor(dev->control);
+	drm_unplug_minor(dev->primary);
+
+	mutex_lock(&drm_global_mutex);
+
+	drm_device_set_unplugged(dev);
+
+	if (dev->open_count == 0) {
+		drm_put_dev(dev);
+	}
+	mutex_unlock(&drm_global_mutex);
+}
+EXPORT_SYMBOL(drm_unplug_dev);

drivers/gpu/drm/drm_vm.c

@@ -680,6 +680,9 @@ int drm_mmap(struct file *filp, struct vm_area_struct *vma)
 	struct drm_device *dev = priv->minor->dev;
 	int ret;
 
+	if (drm_device_is_unplugged(dev))
+		return -ENODEV;
+
 	mutex_lock(&dev->struct_mutex);
 	ret = drm_mmap_locked(filp, vma);
 	mutex_unlock(&dev->struct_mutex);

include/drm/drmP.h

@@ -1170,6 +1170,8 @@ struct drm_device {
 	struct idr object_name_idr;
 	/*@} */
 	int switch_power_state;
+
+	atomic_t unplugged; /* device has been unplugged or gone away */
 };
 
 #define DRM_SWITCH_POWER_ON 0
@@ -1235,6 +1237,19 @@ static inline int drm_mtrr_del(int handle, unsigned long offset,
 }
 #endif
 
+static inline void drm_device_set_unplugged(struct drm_device *dev)
+{
+	smp_wmb();
+	atomic_set(&dev->unplugged, 1);
+}
+
+static inline int drm_device_is_unplugged(struct drm_device *dev)
+{
+	int ret = atomic_read(&dev->unplugged);
+	smp_rmb();
+	return ret;
+}
+
 /******************************************************************/
 /** \name Internal function definitions */
 /*@{*/
@@ -1455,6 +1470,7 @@ extern void drm_master_put(struct drm_master **master);
 
 extern void drm_put_dev(struct drm_device *dev);
 extern int drm_put_minor(struct drm_minor **minor);
+extern void drm_unplug_dev(struct drm_device *dev);
 extern unsigned int drm_debug;
 
 extern unsigned int drm_vblank_offdelay;