linux-kernel - Re: [PATCH 2/3] mfd: cros_ec: Create sysfs attributes for the ChromeOS EC.

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Message-ID: <CAEgFhe+DQrJ6HqGF1_OWZ77Qs-hZLNgX1bHpx5FOt-y-3xh8gA@mail.gmail.com>
Date:	Thu, 20 Nov 2014 10:16:03 -0800
From:	Bill Richardson <wfrichar@...omium.org>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Lee Jones <lee.jones@...aro.org>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>, Simon Glass <sjg@...gle.com>,
	Gwendal Grignou <gwendal@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] mfd: cros_ec: Create sysfs attributes for the
 ChromeOS EC.

On Thu, Nov 20, 2014 at 3:58 AM, Javier Martinez Canillas
<javier.martinez@...labora.co.uk> wrote:
>
> I don't really know why there are two interfaces for this but I guess
> that different user-space utilities use one or another. Maybe the
> ChromiumOS folks can comment on this.

The /dev/cros_ec interface responds to ioctls and is the primary means
by which userspace applications talk to the EC (replacing three really
awkward bus-specific libraries). It emits a simplified version string
when read so that humans can tell if the EC is alive and speaking the
same protocol that the userspace app expects.

The /sys/class/chromeos/cros_ec/* tree was originally envisioned as a
way to provide additional human-readable interfaces to a subset of the
EC commands, but except for the lightbar it's not often used. The
version component here shows all the version-related info that the EC
can provide.

I apologize for the poor kernel conventions used here. In my
ignorance, I apparently chose the worst code possible to use as a
template, and then invented some new stupidness of my own.

Bill
-- 
Art for Art's Sake
Engineering for Money
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