On Thu, 2010-06-17 at 10:41 -0400, Alan Stern wrote: > This patch (as1398b) adds runtime PM support to the SCSI layer. Only > the machanism is provided; use of it is up to the various high-level > drivers, and the patch doesn't change any of them. Except for sg -- > the patch expicitly prevents a device from being runtime-suspended > while its sg device file is open. > > The implementation is simplistic. In general, hosts and targets are > automatically suspended when all their children are asleep, but for > them the runtime-suspend code doesn't actually do anything. (A host's > runtime PM status is propagated up the device tree, though, so a > runtime-PM-aware lower-level driver could power down the host adapter > hardware at the appropriate times.) There are comments indicating > where a transport class might be notified or some other hooks added. > > LUNs are runtime-suspended by calling the drivers' existing suspend > handlers (and likewise for runtime-resume). Somewhat arbitrarily, the > implementation delays for 100 ms before suspending an eligible LUN. > This is because there typically are occasions during bootup when the > same device file is opened and closed several times in quick > succession. > > The way this all works is that the SCSI core increments a device's > PM-usage count when it is registered. If a high-level driver does > nothing then the device will not be eligible for runtime-suspend > because of the elevated usage count. If a high-level driver wants to > use runtime PM then it can call scsi_autopm_put_device() in its probe > routine to decrement the usage count and scsi_autopm_get_device() in > its remove routine to restore the original count. > > Hosts, targets, and LUNs are not suspended while they are being probed > or removed, or while the error handler is running. In fact, a fairly > large part of the patch consists of code to make sure that things > aren't suspended at such times. > > Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > > --- > > Version 2 changes: > > Rebase to apply on top of the revised 1/3 patch. > > Add a KERN_ERR log level to the SCSI_LOG_ERROR_RECOVERY > call, as recommended by checkpatch. > > Incidentally, although I didn't mention it before, this patch assumes > that the 7-part series beginning here: > > http://marc.info/?l=linux-scsi&m=127551091314515&w=2 > > has been merged. > > > Index: usb-2.6/drivers/scsi/scsi_priv.h > =================================================================== > --- usb-2.6.orig/drivers/scsi/scsi_priv.h > +++ usb-2.6/drivers/scsi/scsi_priv.h > @@ -7,6 +7,7 @@ struct request_queue; > struct request; > struct scsi_cmnd; > struct scsi_device; > +struct scsi_target; > struct scsi_host_template; > struct Scsi_Host; > struct scsi_nl_hdr; > @@ -147,7 +148,18 @@ static inline void scsi_netlink_exit(voi > /* scsi_pm.c */ > #ifdef CONFIG_PM_OPS > extern const struct dev_pm_ops scsi_bus_pm_ops; > +#ifdef CONFIG_PM_RUNTIME > +extern void scsi_autopm_get_target(struct scsi_target *); > +extern void scsi_autopm_put_target(struct scsi_target *); > +extern int scsi_autopm_get_host(struct Scsi_Host *); > +extern void scsi_autopm_put_host(struct Scsi_Host *); > #else > +static inline void scsi_autopm_get_target(struct scsi_target *) {} > +static inline void scsi_autopm_put_target(struct scsi_target *) {} > +static inline int scsi_autopm_get_host(struct Scsi_Host *) { return 0; } > +static inline void scsi_autopm_put_host(struct Scsi_Host *) {} You didn't compile this, did you? The compiler gets distinctly annoyed to see an inline function with no actual variable for the argument ... I fixed up this and the one in scsi_device.h James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
