linux-kernel - Re: [PATCH] HID: usbhid: get/put around clearing needs_remote

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Message-ID: <CANLzEkvcm5g_T+FsEQF2UFzS5A2u7CWgdTiEJAxidfxgAE5bHw@mail.gmail.com>
Date:	Fri, 21 Nov 2014 17:00:49 -0800
From:	Benson Leung <bleung@...omium.org>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	johan@...nel.org, Jiri Kosina <jkosina@...e.cz>,
	linux-usb@...r.kernel.org,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sameer Nanda <snanda@...omium.org>
Subject: Re: [PATCH] HID: usbhid: get/put around clearing needs_remote_wakeup

On Fri, Nov 14, 2014 at 1:08 AM, Oliver Neukum <oneukum@...e.de> wrote:
> On Thu, 2014-11-13 at 12:16 -0800, Benson Leung wrote:
>
>> In usbhid_open, usb_autopm_get_interface is called
>> before setting the needs_remote_wakeup flag, and
>> usb_autopm_put_interface is called after hid_start_in.
>>
>> However, when the device is closed in usbhid_close, the same
>> protection isn't there when clearing needs_remote_wakeup. This will
>> add that to usbhid_close as well as usbhid_stop.
>
> Interesting, but this has the side effect of waking devices
> that are asleep just to remove the flag.
>
>         Regards


If devices are already asleep with this flag enabled, that means that
they are presently configured for remote wake.

Waking the device in the case of a close() is appropriate because it
also has the effect of re-suspending the device with the capability
disabled, as it is no longer necessary.

-- 
Benson Leung
Software Engineer, Chrom* OS
bleung@...omium.org
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