From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from kraid.nerim.net (smtp-102-tuesday.nerim.net [62.4.16.102]) by ozlabs.org (Postfix) with ESMTP id 84384DDF17 for ; Wed, 7 Nov 2007 07:31:35 +1100 (EST) Date: Tue, 6 Nov 2007 21:31:32 +0100 From: Jean Delvare To: Matt Sealey Subject: Re: [RFC] Rework of i2c-mpc.c - Freescale i2c driver Message-ID: <20071106213132.58ba7e1c@hyperion.delvare> In-Reply-To: <4730B817.3000201@genesi-usa.com> References: <9e4733910711050714l2aa3a5eeqf5327c3e0d8ca490@mail.gmail.com> <472F7247.9070106@freescale.com> <9e4733910711051230w2d90a710idec3dcfc2e0f5c16@mail.gmail.com> <472F8267.8070106@freescale.com> <472F9086.2060606@genesi-usa.com> <20071106183210.50058019@hyperion.delvare> <4730B817.3000201@genesi-usa.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: Tjernlund , i2c@lm-sensors.org, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Matt, On Tue, 06 Nov 2007 18:53:11 +0000, Matt Sealey wrote: > Jean Delvare wrote: > > On Mon, 05 Nov 2007 21:52:06 +0000, Matt Sealey wrote: > >> Well, all i2c devices have a chip id you can probe for (...) > > > > This statement is completely incorrect. I2C devices do NOT have > > standard ID registers. Some devices have proprietary ID registers, some > > don't, it's really up to the manfacturer. > > All I2C slave devices have to have a 7- or 10-bit address to identify them > by. They *may* not report what they ARE, but this is 9 times out of > 10 a hardware design decision of soldering the chip to a board and > the address is then coded into device trees or hardcoded into drivers. > > Whoever designed the board and has the datasheets knows the address > they're supposed to be at, and the device can accept this. > > You simply cannot entertain an i2c bus with "anonymous and unnumbered > devices", every one has to have an address it responds to, however > it is defined, or it just does not work. Of course, but it is all about addressing, NOT identifying. > WRT cell-index this is an index of the bus on the chip (not the logical > i2c bus but the physical difference between two i2c controllers) and > then any i2c devices which need to be communicated with would be > child nodes, their reg property reflecting their slave address, is > that not correct? I am not familiar with the OF tree, I can't tell, sorry. -- Jean Delvare