Hi Julian, On Mon, Jan 21, 2013 at 07:55:20PM +1100, Julian Calaby wrote: > Hi Aaron, > > On Mon, Jan 21, 2013 at 7:14 PM, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: > > On Mon, Jan 21, 2013 at 02:31:50PM +1100, Julian Calaby wrote: > >> Hi Alan, > >> > >> On Sun, Jan 20, 2013 at 5:46 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > >> > On Sat, 19 Jan 2013, Aaron Lu wrote: > >> >> > closed. Do we want to drop support for that kind of behavior? > >> >> > >> >> I don't think we should drop such support. > >> >> And the safest way to avoid such break is we refine the suspend > >> >> condition for ODD, and using what ZPODD defined condition isn't that > >> >> bad to me: > >> >> - for tray type, no media inside and tray close; > >> >> - for slot type, no media inside. > >> >> While whether tray is closed or not may not be that important, but at > >> >> least we should make sure there is no media inside. > >> >> > >> >> Thoughts? > >> > > >> > That sounds reasonable to me, at least as a first step. If people want > >> > their CD drive to suspend, they can eject the disc. > >> > >> Stupid question: does the kernel know if a CD has audio tracks? > > > > Yes, cdrom module knows that, but the block driver(e.g. sr) doesn't. > > See cdrom_count_tracks in cdrom.c. > > > > May I know if you have an use case that you want to runtime suspend the > > cd drive with a disc inside? That would help us to refine the runtime > > suspend condition. > > The discussion seemed to be restricting when the drive would be > suspended to only occasions where the drive is empty and, where > applicable, closed. I'll admit that I hadn't followed the discussion > enough to know what the restrictions were before that, but this seemed > to be a further restriction, therefore I assumed that you were > originally planning to be able to suspend the drive with a disk > inside. Right, that was the original implementation to allow the cd drive to be runtime suspended even with a disc inside. > > I asked my question in the hope of someone setting up the compromise: > "we could suspend the drive only if the drive is empty and closed, or > a data disc is inside and nobody's using it." > > Personally, providing nobody's using it, and relevant state is stored, > I can't see any reason why you can't suspend a drive with a disc in > it. It is not easy for the OS to tell if the drive is being used or not sometimes :-) Alan has reminded me it is possible for an app to open the block device file(/dev/sr0), issue a command(play audio), then close the device file. >From the OS' point of view, we think nobody is using it. But actually, the drive is playing cd for the user, so we can't suspend the device. I think we can always refine the condition check, but as a first step, I want to be safe and avoid breaking existing functionalities. Thanks, Aaron -- 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
