From mboxrd@z Thu Jan 1 00:00:00 1970 From: Javier Martinez Canillas Subject: Re: [PATCH RESEND v2 3/7] mfd: cros_ec: Add cros_ec_lpc driver for x86 devices Date: Tue, 20 Jan 2015 16:58:00 +0100 Message-ID: <54BE7B08.1010900@collabora.co.uk> References: <1420205572-2640-1-git-send-email-javier.martinez@collabora.co.uk> <1420205572-2640-4-git-send-email-javier.martinez@collabora.co.uk> <20150120081104.GT21886@x1> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150120081104.GT21886@x1> Sender: linux-kernel-owner@vger.kernel.org To: Lee Jones Cc: Olof Johansson , Doug Anderson , Bill Richardson , Simon Glass , Gwendal Grignou , Jonathan Corbet , linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-samsung-soc@vger.kernel.org Hello Lee, On 01/20/2015 09:11 AM, Lee Jones wrote: > On Fri, 02 Jan 2015, Javier Martinez Canillas wrote: > >> From: Bill Richardson >> >> This adds the LPC interface to the Chrome OS EC. Like the >> I2C and SPI drivers, this allows userspace access to the EC. > > I'm fairly certain that this is _not_ an MFD device. Please locate it > to the proper subsystem (input?). > Sorry, it wasn't my intention to use the mfd subsystem as a place to dump random drivers. Is that I still find hard to understand what is the line between what falls under mfd and what doesn't. For example, I see that mfd drivers are for devices which have multiple functions and the mfd driver is the one that spawns the platform devices and provide an interface to access the I/O registers used by the different platform drivers of the sub-devices. So, the Embedded Controller driver (drivers/mfd/cros_ec.c) falls into that category and in fact has been in the mfd driver for a long time. Now, if an mfd device support different type of buses (e.g: i2c, spi, etc) I see that both the core driver and the driver for the transport method are in the drivers/mfd directory. As an example: drivers/mfd/arizona-{core,i2c,spi}.c drivers/mfd/da9052-{core,i2c,spi}.c drivers/mfd/mc13xxx-{core,i2c,spi}.c drivers/mfd/tps65912-{core,i2c,spi}.c drivers/mfd/wm831x-{core,i2c,spi,otp}.c In the cros_ec case, we already have drivers/mfd/cros_ec_{i2c,spi}.c so since the Low Pin Count is another transport method I thought that this driver belonged to the drivers/mfd directory. Now, all those drivers may be wrong and the buses don't belong to the mfd subsystem but then I think we need to document that since it seems that is the correct way to do it just by looking at the other drivers. Best regards, Javier