linux-kernel - Re: [PATCH] at25: DeviceTree support added

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Message-ID: <20111218185329.GA25217@pengutronix.de>
Date:	Sun, 18 Dec 2011 19:53:29 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Frederic LAMBERT <frdrc66@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] at25: DeviceTree support added

Hi,

please also CC devicetree-discuss@...ts.ozlabs.org when adding new bindings.

On Sun, Dec 18, 2011 at 07:13:55PM +0100, Frederic LAMBERT wrote:
> From: Frederic Lambert <frdrc66@...il.com>
> 
> Signed-off-by: Frederic Lambert <frdrc66@...il.com>
> Signed-off-by: Frederic LAMBERT <frdrc66@...il.com>

One is enough :)

> ---
>  Documentation/devicetree/bindings/spi/spi-bus.txt |   19 ++++++
>  drivers/misc/eeprom/at25.c                        |   62 ++++++++++++++++----
>  2 files changed, 68 insertions(+), 13 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
> index e782add..168ac87 100644
> --- a/Documentation/devicetree/bindings/spi/spi-bus.txt
> +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
> @@ -33,6 +33,16 @@ contain the following properties.
>      		shifted clock phase (CPHA) mode
>  - spi-cs-high     - (optional) Empty property indicating device requires
>      		chip select active high
> +For SPI eeprom using driver 'at25', slave nodes shall also contain the
> +following properties.
> +- byte_len        - device RAM size
> +- dev_name        - device name
> +- pagesize        - for writes (see at25.c)
> +- flags           - adressing mode and R/O flag
> +      - bit 0:  8 bits addrs (EE_ADDR1)
> +      - bit 1: 16 bits addrs (EE_ADDR2)
> +      - bit 2: 24 bits addrs (EE_ADDR3)
> +      - bit 3: disallow writes (EE_READONLY)
>  
>  SPI example for an MPC5200 SPI bus:
>  	spi@f00 {
> @@ -54,4 +64,13 @@ SPI example for an MPC5200 SPI bus:
>  			spi-max-frequency = <100000>;
>  			reg = <1>;
>  		};
> +		at25@0 {
> +			compatible = "eeprom,at25";

No, you can't map the platform data 1:1 to the device tree.
The compatible should specify the actual device, for example
"atmel,25320". And from that information you can derive...

> +			byte_len = <131072>;
> +			dev_name = "CY14B101P";

those two and the EE_ADDR.

> +			pagesize = <128>;

This is indeed a valid property, "read-only" would be another one of interest.

Check at24.c and see how it is done there.

Thanks,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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