> Date: Thu, 27 Sep 2007 16:26:56 -0400 > From: stern@xxxxxxxxxxxxxxxxxxx > To: oliver@xxxxxxxxxx > CC: James.Bottomley@xxxxxxxxxxxx; linux-usb-devel@xxxxxxxxxxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx > Subject: Re: [linux-usb-devel] question on flushing buffers and spinning down disk > > On Thu, 27 Sep 2007, Oliver Neukum wrote: > >>>> 1. autosuspend should not be specific to USB >>> >>> Correct. Which means support for it should be added to the SCSI >>> drivers. SCSI autosuspend shouldn't be kluged into usb-storage in a >>> way that basically ignores what the SCSI layer is doing. >> >> It isn't. The decision to autosuspend is based on activity on the bus. >> Now you might argue that the decision to do an autosuspend should >> always propagate upwards from the lowest level of the device tree. >> Then I ask why? >> Err, why? After all, there's a central instance in userspace that decides >> that the whole system isn't used right now. I see no reason to not use >> this model for parts of the device tree. > > Autoresume is the major complication. > > There's also a philosophical objection. Who is in a better position to > judge when a device like a SCSI drive should be autosuspended: its own > driver (sd) or someone else (usb-storage)? > Isn't power saving a policy decision? Should it not be left to userspace to control? Doesn't userspace decide to blank the video based on user preferences? Userspace could jump through all sorts of hoops to wait for disks to spin down, etc on the way to powersaving. If we really need the capability to suspend a mouse/keyboard etc after 2-n seconds of no use, shouldn't it be userspace that enables the "autosuspend"? Has the battery life impact of the various device shutdowns been measured and found useful? Just a bunch of questions, but it seems to me that what is really needed is a mechanism for userspace to do fine grained power control. Regards, Steve _________________________________________________________________ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-us&source=wlmailtagline- 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
