The ODD can either be runtime resumed by the user or by a software
request. And for the latter part, we only support runtime resume the ODD
when the eject request is received. We did this in sr's block ioctl
function, this looks ugly.

Change this by runtime resuming the ODD in its open function and runtime
suspending it in its release function.

The downside of this approach is that in old distros with old udisk
daemon, the ODD will be polled by udisk daemon so open/close will
constantly be called, which will cause the ODD frequently resume from
suspend state, breaking the effect of power saving. User with such a
distro is advised to issue a udisk command to inhibit polling of the
disk like this:
$ udisks --inhibit-polling /dev/sr0
And since newer kernel has in kernel polling, there is no problem
regarding ODD's event report.

Signed-off-by: Aaron Lu <redacted>
---
 drivers/scsi/sr.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 5f4d19a..f7a7635 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c

@@ -152,8 +152,15 @@ static inline struct scsi_cd *scsi_cd_get(struct gendisk *disk)
 	kref_get(&cd->kref);
 	if (scsi_device_get(cd->device))
 		goto out_put;
+	if (pm_runtime_get_sync(&cd->device->sdev_gendev) < 0) {
+		pm_runtime_put_noidle(&cd->device->sdev_gendev);
+		goto out_pm;
+	}