On Fri, Jun 27, 2008 at 10:57:39PM +0200, Oliver Neukum wrote:

Am Freitag 27 Juni 2008 22:51:47 schrieben Sie:

quoted

quoted

quoted

Ah, so it resumes the device even if it was not autosuspended but
suspended for another reason?

The other reason is either system wide, in which case nobody can call open,
or it is forcibly suspended via sysfs, causing usb_submit_urb() to fail later
on.

Which will also fail the open() itself. Isn't that bad? That is, you can
suspend an already open device without the users the device noticing
but you can't open it if you happen to suspend it at just the right time.
That doesn't strike me as good behaviour for a driver.

Root can also unbind the driver.

Sure, but in that case the behavior is consistent ie. the device
disappears.

There is no behavior pleasing everybody.

I would just prefer all drivers of the same subsystem to behave in a
consistent manner. It would even make sense to document the desired
behavior so future driver writers wouldn't have to come up with their
own private rules for such things.

As it stands the open can fail in seemingly random fashion which would
be bad for the users. And my opinion (if it counts) is to allow the open
to succeed for suspended devices since already opened devices would not
notice the suspend either. I don't think there's any downside to handling
this issue apart from adding a couple of lines of code.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/
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