From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ray Jui Subject: Re: [PATCH v1 1/1] i2c: iproc: Add i2c repeated start capability Date: Tue, 3 Sep 2019 16:11:16 -0700 Message-ID: <540c4e2d-0dd5-5260-30b2-e1589b279d71@broadcom.com> References: <1565150941-27297-1-git-send-email-rayagonda.kokatanur@broadcom.com> <20190830125626.GC2870@ninjato> <3e70fa7e-de13-4edd-2e17-b7c56e91d220@broadcom.com> <20190831094940.GA1138@kunai> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190831094940.GA1138@kunai> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Wolfram Sang Cc: Rayagonda Kokatanur , Rob Herring , Mark Rutland , linux-i2c@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, Florian Fainelli , Lori Hikichi , Icarus Chau , Shivaraj Shetty List-Id: devicetree@vger.kernel.org On 8/31/19 2:49 AM, Wolfram Sang wrote: > Hi Ray, > >>> With all the limitations in place, I wonder if it might be easier to >>> implement an smbus_xfer callback instead? What is left that makes this >>> controller more than SMBus and real I2C? >>> >> >> Right. But what is the implication of using smbus_xfer instead of >> master_xfer in our driver? >> >> Does it mean it will break existing functions of the i2c app that our >> customers developed based on i2cdev (e.g., I2C_RDWR)? > > If the customers uses I2C_RDWR (and it cannot be mapped to i2c_smbus_* > calls) then this is an indication that there is some I2C functionality > left which the HW can provide. I'd be interested which one, though. > >> >> 1) Does > > Maybe you wanted to describe it here and it got accidently cut off? > I think you are right that the controller does not seem to support additional I2C features in addition to SMBUS. However, my concern of switching to the smbus_xfer API is: 1) Some customers might have used I2C_RDWR based API from i2cdev. Changing from master_xfer to smbus_xfer may break the existing applications that are already developed. 2) The sound subsystem I2C regmap based implementation seems to be using i2c_ based API instead of smbus_ based API. Does this mean this will also break most of the audio codec drivers with I2C regmap API based usage? Thanks, Ray > Regards, > > Wolfram >