linux-kernel - Re: [PATCH] Input: atkbd - fix LED state at suspend/resume

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Message-ID: <64DEA81E07C8F88E+20240805155136.6212f08d@john-PC>
Date: Mon, 5 Aug 2024 15:51:36 +0800
From: Qiang Ma <maqianga@...ontech.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: hdegoede@...hat.com, linux-input@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: atkbd - fix LED state at suspend/resume

On Fri, 26 Jul 2024 14:57:03 -0700
Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:

> On Fri, Jul 26, 2024 at 02:57:03PM -0700, Dmitry Torokhov wrote:
> > Hi Qiang,
> > 
> > On Fri, Jul 26, 2024 at 06:27:30PM +0800, Qiang Ma wrote:
> > > After we turn on the keyboard CAPSL LED and let the system
> > > suspend, the keyboard LED is not off, and the kernel log is as
> > > follows:
> > > 
> > > [  185.987574] i8042: [44060] ed -> i8042 (kbd-data)
> > > [  185.988057] i8042: [44061] ** <- i8042 (interrupt, 0, 1)
> > > [  185.988067] i8042: [44061] 04 -> i8042 (kbd-data)
> > > [  185.988248] i8042: [44061] ** <- i8042 (interrupt, 0, 1)
> > > 
> > > The log shows that after the command 0xed is sent, the data
> > > sent is 0x04 instead of 0x00.
> > > 
> > > Solution:
> > > Add a bitmap variable ledon in the atkbd structure, and then set
> > > ledon according to code-value in the event, in the atkbd_set_leds
> > > function, first look at the value of lenon, if it is 0, there is
> > > no need to look at the value of dev->led, otherwise, Need to look
> > > at dev->led to determine the keyboard LED on/off.
> > 
> > I am not sure why duplicating input_dev->led which is supposed to
> > record which LEDs are currently active on an input device would
> > solve the issue. Could you please explain?
> 
> Ah, OK, I see it now. We do not actually toggle input_dev->led when
> suspending, so atkbd uses wrong data to determine the LED state.
> 

Yes, that's true.

> > 
> > The input core is supposed to turn off all LEDs on suspend. This
> > happens in input_dev_toggle() which is called from
> > input_dev_suspend(). It iterates over all LEDs on a device and
> > turns off active ones one by one.
> > 
> > I think what happens here is we are running afoul of the throttling
> > done in atkbd (see atkbd_schedule_event_work), and it does not
> > actually turn off all LEDs in time. But on the other hand
> > atkbd_cleanup() (which is called to suspend the keyboard) calls
> > 
> >     ps2_command(&atkbd->ps2dev, NULL, ATKBD_CMD_RESET_DEF);
> > 
> > which should turn off everything anyways.
> 
> But still, why ATKBD_CMD_RESET_DEF does not shut off the LEDs for you?
> 
Looking at a ps/2 keyboard
document(http://www-ug.eecg.toronto.edu/msl/nios_devices/datasheets/PS2%20Keyboard%20Protocol.htm),
the F6 command does not seem to affect the state of the LED.

> Thanks.
> 
> -- 
> Dmitry

--
Qiang