linux-kernel - Re: [PATCH 3/4] spi: Add OF binding support for SPI busses

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Date:	Fri, 16 May 2008 13:47:20 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linuxppc-dev@...abs.org, spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, dbrownell@...rs.sourceforge.net,
	fabrizio.garetto@...il.com, jonsmirl@...il.com
Subject: Re: [PATCH 3/4] spi: Add OF binding support for SPI busses

On Fri, 16 May 2008 13:36:13 -0600 Grant Likely wrote:

> diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
> index 1d2a772..452c242 100644
> --- a/Documentation/powerpc/booting-without-of.txt
> +++ b/Documentation/powerpc/booting-without-of.txt
> @@ -2870,6 +2871,66 @@ platforms are moved over to use the flattened-device-tree model.
>  		reg = <0xe8000000 32>;
>  	};
>  
> +    s) SPI (Serial Peripheral Interface) busses
> +
> +    SPI busses can be described with a node for the SPI master device
> +    and a set of child nodes for each SPI slave on the bus.  For this
> +    discussion, it is assumed that the system's SPI controller is in
> +    SPI master mode.  This binding does not describe SPI controllers
> +    in slave mode.
> +
> +    The SPI master node requires the following properties:
> +    - #address-cells  - number of cells required to define a chip select
> +			address on the SPI bus.
> +    - #size-cells     - should be zero.
> +    - compatible      - name of SPI bus controller following generic names
> +			recommended practice.
> +    No other properties are required in the spi bus node.  It is assumed
                                               ~~~

> +    that a driver for an SPI bus device will understand that it is an SPI bus.
> +    However, the binding does not attempt to define the specific method for
> +    assigning chip select numbers.  Since SPI chip select configuration is
> +    flexible and non-standardized, it is left out of this binding with the
> +    assumption that board specific platform code will be used to manage
> +    chip selects.  Individual drivers can define additional properties to
> +    support describing the chip select layout.
> +
> +    SPI slave nodes must be children of the spi master node and can
                                               ~~~

> +    contain the following properties.
> +    - reg             - (required) chip select address of device.
> +    - compatible      - (required) name of SPI device following generic names
> +			recommended practice
> +    - max-speed       - (optional) Maximum SPI clocking speed of device in Hz
> +    - spi,cpol        - (optional) Device requires inverse clock polarity
> +    - spi,cpha        - (optional) Device requires shifted clock phase
> +    - linux,modalias  - (optional, Linux specific) Force binding of SPI device
> +			to a particular spi_device driver.  Useful for changing
> +			driver binding between spidev and a kernel spi driver.
                                                                   ~~~

Hi,
You mostly capitalize "SPI" in sentences (i.e., when it's not part of
a function name or OF data), so could the 3 underlined instances of it
also be all caps?

Thanks,
---
~Randy
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