From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: [PATCH 3/4] spi: Add OF binding support for SPI busses Date: Thu, 22 May 2008 19:26:23 -0700 Message-ID: <200805221926.24112.david-b@pacbell.net> References: <20080516193054.28030.35126.stgit@trillian.secretlab.ca> <716a0f1b6c9a544b480c06a329072483@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: fabrizio.garetto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Segher Boessenkool , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linuxppc-dev-mnsaURCQ41sdnm+yROfE0A@public.gmane.org, Guennadi Liakhovetski To: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org On Wednesday 21 May 2008, Grant Likely wrote: > > spi-controller { > > =A0 =A0 =A0 =A0#address-cells =3D 2; > > =A0 =A0 =A0 =A0#size-cells =3D 0; > > =A0 =A0 =A0 =A0some-device@0,f000 { reg =3D < 0 f000 >; } // CS 0, SPI = address f000 > > =A0 =A0 =A0 =A0some-device@1,f000 { reg =3D < 1 f000 >; } // CS 1, SPI = address f000 > > =A0 =A0 =A0 =A0some-device@1,ff00 { reg =3D < 1 ff00 >; } // CS 1, SPI = address ff00 > > } > = > For SPI the CS # *is* the address. =A0:-) > = > Unlike I2C, SPI doesn't impose any protocol on the data. =A0It is all > anonymous data out, anonymous data in, a clock and a chip select. Very true ... but then there are SPI chips which embed addressing. I have in mind the mcp23s08 (and mcp23s17) GPIO expanders, which support up to four chips wired in parallel on a given chipselect. The devices are distinguished by how two address pins are wired; and two bits in the command byte must match them. (I think they just recycled an I2C design into the SPI world.) - Dave ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/