Hi, Alan, On Mon, 2012-02-06 at 10:13 -0500, Alan Stern wrote: > On Mon, 6 Feb 2012, Huang Ying wrote: > > > SSD becomes more and more popular, this makes it possible to put disk into > > low power state more often. And request based runtime PM for scsi disk is > > more useful than open/close based one because disk is normally mounted at > > most time. > > > > One known issue, because SCSI TEST_UNIT_READY will be put into request > > queue every 2 seconds by default, this makes it hard for disk to sleep. > > Maybe we can implement check_events callback in some other way? > > > > [RFC 1/5] pm, runtime, Add resume notifier > > [RFC 2/5] scsi, pm, rename scsi_autopm_get/put_xxx to > > [RFC 3/5] scsi, pm, add pm_runtime_get/put in scsi request > > [RFC 4/5] scsi, pm, use autosuspend for scsi runtime PM > > [RFC 5/5] scsi, sd, pm, request based runtime PM support > > Your whole approach is at the wrong level. Runtime PM between I/O > requests for block devices should be implemented in the block layer, > not in the SCSI layer. > > It also is much more difficult than your patches would indicate. For > example, some USB card readers indicate a media change every time they > resume; therefore they must not be suspended while the device file is > open. > > Another difficulty arises because some drivers need to send SCSI > commands (such as SYNCHRONIZE CACHE) _while_ suspending or resuming. Thank you very much for your valuable response! We will do more research work on this topic, including your previous effort. :) Best Regards, Huang Ying -- 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
