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SubjectRe: [PATCH 2/3] mfd: cros_ec: Create sysfs attributes for the ChromeOS EC.
Hello Lee,

On 11/18/2014 03:26 PM, Lee Jones wrote:
> On Mon, 17 Nov 2014, Javier Martinez Canillas wrote:
>> From: Bill Richardson <>
>> This adds the first few sysfs attributes for the Chrome OS EC. These
>> controls are made available under /sys/devices/virtual/chromeos/cros_ec
>> flashinfo - display current flash info
> drivers/mtd?
>> reboot - tell the EC to reboot in various ways
> drivers/power?

Well this driver is special in the sense that there is a Cortex-M Embedded
Controller that has different peripherals (flash, keyboard, charger, etc).
The kernel communicates with these peripherals by using a tunnel through
the protocol used to communicate with the Embedded Controller (SPI/I2C/LPC).

But you are right that this is not suitable for drivers/mfd, I just added
there because that is the location in the downstream ChromeOS kernel but
like you said, the MFD subsystem should not be a dumping ground for devices
that is not clear where should live.

On v2 I'll add this sysfs interface and the dev to drivers/platform/chrome/
since I think is a better place for the cros_ec dev driver. It will still
be spawns from the cros_ec MFD driver though but that is OK for you AFAIU.

>> version - information about the EC software and hardware
> What's the difference between this version and the version you can
> read in the new _dev driver?

The version information read from the cros_ec dev interface is a subset
of the information read from the version sysfs, e.g:

$ cat /dev/cros_ec

$ cat /sys/class/chromeos/cros_ec/version
RO version: pit_v1.1.1198-1cd618e
RW version: pit_v1.1.1198-1cd618e
Firmware copy: RO
Build info: pit_v1.1.1198-1cd618e 2014-04-30 16:29:52 @build122-m2
Chip vendor: stm
Chip name: stm32l15x
Chip revision:
Board version: 0

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.

Best regards,

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