On Saturday, September 22, 2012, Alan Stern wrote: > On Sat, 22 Sep 2012, Rafael J. Wysocki wrote: > > > > There are sd devices with removable media. > > > > OK. Does the SCSI layer distinguish them from devices without removable media? > > Yes, it does. struct scsi_device has a .removable member, and the > Removable flag is part of the response data to the INQUIRY command > (which belongs to the primary command set common to all SCSI devices). > > > > > User space has an interface to disable runtime PM of any device and it looks > > > > like that interface should be sufficient to disable the feature in question. > > > > Why do you think the new interface is needed? > > > > > > Because this is not equivalent to doing no runtime PM at all. SCSI > > > now defines some powersaving states which do not involve powering > > > down and thus losing state. > > > > I see. So the sr's runtime suspend may be useful even without the power-off > > feature, right? > > Exactly. Even though the drive itself may not be powered off, by > putting it into runtime suspend we gain the ability to suspend the > ancestor devices. OK, so what about using a PM QoS-based approach as described (in general terms) in this message in the "USB ports power off" thread: http://marc.info/?l=linux-pm&m=134831537224566&w=4 Rafael -- 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
