linux-kernel - Re: [PATCH][RFC] usbhid: enable autosuspend for internal devices

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Date:	Mon, 29 Jun 2015 13:16:51 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Oliver Neukum <oneukum@...e.com>
cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Tom Gundersen <teg@...m.no>, linux-usb@...r.kernel.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC] usbhid: enable autosuspend for internal devices

On Mon, 29 Jun 2015, Oliver Neukum wrote:

> > Last time we were testing this, autosuspend for USB HID devices was quite 
> > a disaster.
> > 
> > Do you have any idea whether udev developers tested the "autosuspend on by 
> > default for USB HID devices" on reasonable set of devices?
> > 
> > The culrpits that I remember from top of my head (it's been long time 
> > ago):
> > 
> > - the LEDs for suspended device go off. This is very confusing at least on 
> >   keyboards, and brings really bad user experience
> 
> That is a bug. hidinput_count_leds() is supposed to prevent that.

This is a HW property and nothing kernel can do about. I am not saying it 
doesn't bring the LEDs up to a proper state again once auto-resumed. But I 
hate the LEDs going off a few seconds after I stop typing (i.e. once the 
keyboard gets auto-suspended).

-- 
Jiri Kosina
SUSE Labs
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