path: root/include/scsi
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authorAlan Stern <stern@rowland.harvard.edu>2010-06-17 10:41:42 -0400
committerJames Bottomley <James.Bottomley@suse.de>2010-07-28 09:07:50 -0500
commitbc4f24014de58f045f169742701a6598884d93db (patch)
tree4e68ae6fa5fff179ce69b2d890b01a5fcc9c55d5 /include/scsi
parentdb5bd1e0b505c54ff492172ce4abc245cf6cd639 (diff)
[SCSI] implement runtime Power Management
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. [jejb: fix up compile issues in PM config variations] Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Diffstat (limited to 'include/scsi')
1 files changed, 8 insertions, 0 deletions
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index d80b6dbed1c..50cb34ffef1 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -381,6 +381,14 @@ extern int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
struct scsi_sense_hdr *, int timeout, int retries,
int *resid);
+extern int scsi_autopm_get_device(struct scsi_device *);
+extern void scsi_autopm_put_device(struct scsi_device *);
+static inline int scsi_autopm_get_device(struct scsi_device *d) { return 0; }
+static inline void scsi_autopm_put_device(struct scsi_device *d) {}
+#endif /* CONFIG_PM_RUNTIME */
static inline int __must_check scsi_device_reprobe(struct scsi_device *sdev)
return device_reprobe(&sdev->sdev_gendev);