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



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