From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Carpenter Subject: Re: [RESEND2 PATCH v4 2/2] i2c: sunxi: add P2WI (Push/Pull 2 Wire Interface) controller support Date: Tue, 10 Jun 2014 09:56:40 +0100 Message-ID: <5396C848.8020701@pcserviceselectronics.co.uk> References: <1401785392-26602-1-git-send-email-boris.brezillon@free-electrons.com> <1401785392-26602-3-git-send-email-boris.brezillon@free-electrons.com> <20140610083850.GB2620@katana> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140610083850.GB2620@katana> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: Boris BREZILLON , Andrew Morton , Greg Kroah-Hartman , Randy Dunlap , Maxime Ripard , Hans de Goede , Shuge , kevin-0TFLnhJekD6UEPyfVivIlAC/G2K4zDHf@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org Wolfram Sang wrote: > On Tue, Jun 03, 2014 at 10:49:52AM +0200, Boris BREZILLON wrote: >> The P2WI looks like an SMBus controller which only supports byte data >> transfers. But, it differs from standard SMBus protocol on several >> aspects: >> - it supports only one slave device, and thus drop the address field >> - it adds a parity bit every 8bits of data >> - only one read access is required to read a byte (instead of a read >> followed by a write access in standard SMBus protocol) Minor quibble should be "(instead of a write followed by a read access in standard SMBus protocol)" That being similar to EEPROM and other types of devices write internal address followed by read access from internal address. >> - there's no Ack bit after each byte transfer >> >> This means this bus cannot be used to interface with standard SMBus >> devices (the only known device to support this interface is the AXP221 >> PMIC). > > Good description. Should be a comment at the top of the driver to spread > the word. -- Paul Carpenter | paul-YHLC2tV1sDlxR4N9A70vTlRxknfHcPLb9dF7HbQ/qKg@public.gmane.org PC Services Raspberry Pi Add-ons Timing Diagram Font For those web sites you hate