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>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 6263b014759..7348a3dab25 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/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);