On Tuesday, November 20, 2012 04:59:57 PM Aaron Lu wrote: > On 11/20/2012 02:00 PM, Aaron Lu wrote: > > On 11/19/2012 10:56 PM, Tejun Heo wrote: > >> I really think we need a way for (auto)pm and event polling to talk to > >> each other so that autopm can tell event poll to sod off while pm is > >> in effect. Trying to solve this from inside libata doesn't seem > >> right. The problem, again, seems to be figuring out which hardware > >> device maps to which block device. Hmmm... Any good ideas? > > > > A possible way of doing this is using pm qos. > > > > We currently have 2 pm qos flags, NO_POWER_OFF and REMOTE_WAKEUP, and we > > can add another one: NO_POLL, use it like the following: > > 1 Set the NO_POLL pm qos flag when the underlying driver thinks it is no > > longer necessary. In the ZPODD's case, it should be set when the > > device is to be powered off; > > 2 Clear it when poll is necessary again. In the ZPODD's case, when power > > is re-gained, this flag will be cleared. > > > > 3 In the disk_events_workfn, check if this flag is set, if so, simply > > return. > > It should be, skip calling disk->fops->check_events, but still queue the > work for next time's poll. > > -Aaron > > > > > The disk->driverfs_dev can be used to host the pm qos flag, ATA layer > > can access it through ata_device->sdev->sdev_gendev. > > > > Is this OK? No, I don't think so. PM QoS is about telling the layer that will put the device into low-power states what states are to be taken into consideration. In this case, however, we need to tell someone else that the device has been turned off. Clearly, we need a way to do that, but not through PM QoS. Did you consider using pm_runtime_suspended() to check the device status? Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
