linux-kernel - Re: [PATCH RESEND v2 5/7] mfd: cros_ec: Instantiate ChromeOS EC character device

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54BFDA51.7020609@collabora.co.uk>
Date:	Wed, 21 Jan 2015 17:56:49 +0100
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Lee Jones <lee.jones@...aro.org>
CC:	Olof Johansson <olof@...om.net>,
	Doug Anderson <dianders@...omium.org>,
	Bill Richardson <wfrichar@...omium.org>,
	Simon Glass <sjg@...gle.com>,
	Gwendal Grignou <gwendal@...gle.com>,
	Jonathan Corbet <corbet@....net>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v2 5/7] mfd: cros_ec: Instantiate ChromeOS EC character
 device

Hello Lee,

On 01/20/2015 06:11 PM, Javier Martinez Canillas wrote:
>> 
>> But is it really a chardev?  Don't chardevs usually live in
>> drivers/char?  It probably uses a chardev node in /dev, but what does
>> it really do?  What information can/will userspace obtain from this
>> memory block?
>> 
> 
> Right, is a driver that register a chardev but mostly to expose an ioctl
> interface to send commands to the Embedded Controller from user-space.
> 
> The Application Processor communicates with Embedded Controller by sending
> commands over an interface. This can be either spi or i2c on ARM (depending
> on the Chromebook model) or LPC on x86 Chromebooks so the platform driver
> instantiated by the "cros-ec-dev" mfd cell is to allow user-space to send
> commands to the Embedded Controller (using the correct transport method).
> 
> So this chardev is used by the ectool binary in ChromeOS to communicate
> with the Embedded Controller.
> 

Just FYI, I'll rename it to "cros-ec-ctl" since as you said is not really
a chardev but that just happens to be the interface chosen to send the ioctl
commands to the driver.

Thanks a lot for your suggestion.

Best regards,
Javier
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/