linux-kernel - Re: [PATCH 2/3] HID: usbhid: hid-core: submit queued urbs before suspend

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Date:	Wed, 14 Dec 2011 10:14:33 +0100
From:	Oliver Neukum <oneukum@...e.de>
To:	Daniel Kurtz <djkurtz@...omium.org>
Cc:	jkosina@...e.cz, bleung@...omium.org, stern@...land.harvard.edu,
	olofj@...omium.org, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 2/3] HID: usbhid: hid-core: submit queued urbs before suspend

Am Mittwoch, 14. Dezember 2011, 09:00:18 schrieb Daniel Kurtz:
> On Wed, Dec 14, 2011 at 3:55 PM, Oliver Neukum <oneukum@...e.de> wrote:
> > Am Donnerstag, 17. November 2011, 12:23:49 schrieb Daniel Kurtz:
> >> Unfortunately, this usually happens while the first LED request is
> >> actually still being processed.  Thus when the completion handler tries
> >> to submit the second LED request it fails, since REPORTED_IDLE is
> >> already set!  This REPORTED_IDLE check failure causes the completion
> >> handler to complete, however without clearing the CTRL_RUNNING flag.
> >> This, in turn, means that the suspend() handler's wait_io() condition
> >> is never satisfied, and instead it times out after 10 seconds, aborting
> >> the original system suspend.
> >>
> >> This patch changes the behavior to the following:
> >>   (1) allow completion handler to finish submitting all queued URBs, even if
> >>       REPORTED_IDLE is set.  This guarantees that all URBs queued before the
> >>       hid-core suspend() call will be submitted before the system is
> >>       suspended.
> >
> > Hi,
> >
> > why is this desirable? You'd want to requests to be executed at resumption.
> > A system suspend will alter the LED state anyway.
> 
> This is how a system suspend 'alters' the LED state.  The input layer
> sends those LED off commands down through HID as it is trying to
> suspend.  We want to make sure the usbhid layer actually finishes
> forwarding those requests on to the device before the system is
> suspended.

You know the HID layer will send those commands. You don't know which
other commands may already be queued. So I don't know whether you really want
to execute them all while the system is asuspending.

	Regards
		Oliver
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