Re: [PATCH 2/5] scsi: sr: runtime pm when ODD is open/closed

Alan Stern
2012-07-23T14:57:30Z

On Mon, 23 Jul 2012, Aaron Lu wrote:

> 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 <aaron.lu@amd.com>
> ---
> 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;
> + }

You should use scsi_autopm_get_device instead of bypassing the SCSI
layer. Similarly for the _put call.

I know the existing calls do this already. They shouldn't.

Alan Stern