linux-kernel - Re: [PATCH] Input: cros_ec_keyb: add support for base attached event

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Message-ID: <ZaovKvmhEsEO41ti@google.com>
Date: Fri, 19 Jan 2024 00:13:30 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: ☆★☆ Ting ☆★☆ Shen <phoenixshen@...gle.com>
Cc: Ting Shen <phoenixshen@...omium.org>,
	LKML <linux-kernel@...r.kernel.org>, fshao@...omium.org,
	Benson Leung <bleung@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Guenter Roeck <groeck@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	chrome-platform@...ts.linux.dev,
	joewu (吳仲振) <joewu@....com>,
	linux-input@...r.kernel.org
Subject: Re: [PATCH] Input: cros_ec_keyb: add support for base attached event

On Fri, Jan 19, 2024 at 03:47:32PM +0800, ☆★☆ Ting ☆★☆ Shen wrote:
> On Fri, Jan 19, 2024 at 1:55 AM Dmitry Torokhov <dmitry.torokhov@...il.com>
> wrote:
> 
> > Hi Ting,
> >
> > On Thu, Jan 18, 2024 at 04:52:43PM +0800, Ting Shen wrote:
> > > This CL maps ChromeOS EC's BASE_ATTACHED event to SW_DOCK,
> >
> > As far as I know none of the Chrome OS devices support classic docking
> > station (not talking about the new USB-C/TB ones).
> >
> > > to allow userspace detect that a keyboard is attached to the
> > > detachable device.
> >
> > Are we planning to have detachable keyboard that is not USB?
> >
> Yes this is for a non-USB keyboard. The keyboard is connected to EC, and EC
> forwards input events to the host.
> 
> >
> > EC_MKBP_BASE_ATTACHED is processed by hid-google-hammer driver and,
> > together with the USB connector state, is used to form SW_TABLET_MODE.
> > The reason just the USB state was not enough is because the keyboard
> > could be attached to the lid "other way around" to be used as a stand.
> > In that configuration USB connection was not active. However userspace
> > still needed to know about this to activate tablet version of the UI.
> >
> > Please provide more information why you want this to be exposed via
> > cros_ec_keyb driver.
> >
> > Thanks.
> >
> 
> The main purpose of this patch is to have some signal to trigger the
> firmware updater (hammerd), EC_MKBP_BASE_ATTACHED seems suitable.
> EC_MKBP_TABLET_MODE is also usable but may be too noisy, it fires whenever
> the user flips the keyboard.

I think this can be solved in userspace. You may consider emitting
uevent when seeing EC_MKBP_BASE_ATTACHED from the EC. SW_DOCK input event
is not really suitable here as it indicated a docking station being
attached.

Thanks.

-- 
Dmitry