Am Dienstag, 31. August 2010, 18:59:01 schrieb Alan Stern:
> On Tue, 31 Aug 2010, Oliver Neukum wrote:
> Ah yes. In fact, that must be a problem even now. At least adding
> autosuspend support won't make it any worse than it already is.
Oh, there's another little problem in autosuspend_check()
/* Don't allow autosuspend if the device will need
* a reset-resume and any of its interface drivers
* doesn't include support or needs remote wakeup.
*/
if (udev->quirks & USB_QUIRK_RESET_RESUME) {
struct usb_driver *driver;
driver = to_usb_driver(intf->dev.driver);
if (!driver->reset_resume ||
intf->needs_remote_wakeup)
return -EOPNOTSUPP;
This means devices with this quirk will be suspended. Which in means
that medium change events will be lost. I think for devices with this quirk
we can autosuspend only if there's no medium present. Furthermore
you'll probably need to introduce a new flag to signal this requirement
to usbcore.
> > > For those buggy readers, it would be better to have something
> > > which could be implemented as a sysfs attribute in usb-storage.
> >
> > Why usb-storage? Any drive for real rotational media has the same
> > requirement.
> > Waiting for minutes for a suspend without medium is ridiculous,
> > as is spinning down a disk after only two seconds.
>
> Suggestions for a sysfs interface? Should the sd driver add its own
> "suspend_delay_no_medium" attribute?
Hm. I see no connection to sd. In fact I see no connection to block
devices. Tapes have this issue, too.
Regards
Oliver
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