From mboxrd@z Thu Jan 1 00:00:00 1970 From: Qiao Zhou Subject: Re: [PATCH 1/3] mfd: support 88pm80x in 80x driver Date: Tue, 03 Jul 2012 10:28:39 +0800 Message-ID: <4FF258D7.8050109@marvell.com> References: <1340853214-5429-1-git-send-email-zhouqiao@marvell.com> <20120702101228.GD25093@opensource.wolfsonmicro.com> <4FF174AA.3020001@marvell.com> <201207021558.51246.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201207021558.51246.arnd-r2nGTMty4D4@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Arnd Bergmann Cc: Mark Brown , "haojian.zhuang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , Chao Xie , "rpurdie-Fm38FmjxZ/leoWH0uzbU5w@public.gmane.org" , "sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , Wilbur Wang , "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-i2c@vger.kernel.org On 07/02/2012 11:58 PM, Arnd Bergmann wrote: > On Monday 02 July 2012, Qiao Zhou wrote: >> On 07/02/2012 06:12 PM, Mark Brown wrote: >>> On Mon, Jul 02, 2012 at 06:09:57PM +0800, Qiao Zhou wrote: >>>> On 07/02/2012 06:03 PM, Mark Brown wrote: >>> >>>>> What do you mean by pages? regmap has paging support which just maps >>>>> everything into a single flat register map from the point of view of >>>>> callers. >>> >>>> Mark, let me explain: the 88pm800 chip has three i2c address >>>> internally, which we called different page instead. it confuses you >>>> with the register page_read/write operation. there are registers in >>>> each i2c address domain, and we need to use different i2c client to >>>> access reg in different domain. such as some common regs are in the >>>> page of i2c_addr = 0x30, and power related regs are in the page of >>>> i2c_addr = 0x31, and gpadc related regs are in the page of 0x32. >>> >>> These aren't what people normally call pages, those are just separate >>> I2C devices from a Linux point of view. >>> >> Mark, surely I'll pay attention to the terms used. thanks! >> due to there separate I2C devices, does it make sense to export separate >> r/w interface for them? do you have suggestion in such case? > > (adding the i2c mailing list to get more insight) > > I think in case of device tree based probing, it would be straightforward > to represent 88pm800 as a single device with three addresses in the "reg" > property, while the natural linux representation would be one regular > i2c_client device with two dummies. Do we or should we have any > infrastructure to deal with this? > > If this is a common scenario, we could probably let regmap handle it > entirely internally and represent the i2c client with its dummies > as a single regmap. actually there are many drivers under mfd which have this common issue, which has i2c dummy devices, such as max77693.c, max8925-i2c.c, ab3100-core.c, max8997.c, max8998.c, s5m-core.c etc. some use regmap handle directly as param in exported r/w api, some add extra param to differentiate i2c dummy. it seems to be a common scenario. how do we handle the API in short term and long term? > > Arnd > -- Best Regards Qiao