linux-kernel - Re: [PATCH 1/1] generic spidev devices must be registered

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Date:	Fri, 5 Aug 2016 14:43:43 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Fabien Lahoudere <fabien.lahoudere@...labora.co.uk>
Cc:	Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
	"open list:SPI SUBSYSTEM" <linux-spi@...r.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] generic spidev devices must be registered

On Fri, Aug 05, 2016 at 03:11:53PM +0200, Fabien Lahoudere wrote:
> Adding spidev in the compatible list, let configure spidev from device tree
> instead of C source code.

I'm not keen on this.

It ties the hardware description to today's use-case, and leaves the DT
without information regarding the particuarl device. The binding is also
written in terms of the userspace interface, which is backwards.

So NAK to this as-is.

Thanks,
Mark.

> 
> Signed-off-by: Fabien Lahoudere <fabien.lahoudere@...labora.co.uk>
> ---
>  Documentation/devicetree/bindings/spi/spidev.txt | 16 ++++++++++++++++
>  drivers/spi/spidev.c                             |  1 +
>  2 files changed, 17 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/spi/spidev.txt
> 
> diff --git a/Documentation/devicetree/bindings/spi/spidev.txt b/Documentation/devicetree/bindings/spi/spidev.txt
> new file mode 100644
> index 0000000..23200f2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/spi/spidev.txt
> @@ -0,0 +1,16 @@
> +* SPIDEV
> +
> +spidev is a device driver to access to SPI devices using normal userspace I/O calls.
> +To make an SPI device compatible with this drivers add:
> +
> +Required properties:
> +- compatible : should be "spidev".
> +
> +Example:
> +
> +spidev0: spi@0 {
> +	compatible = "spidev";
> +	reg = <0>;
> +	spi-max-frequency = <1000000>;
> +	status = "okay";
> +};
> diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
> index 2e05046..d780491 100644
> --- a/drivers/spi/spidev.c
> +++ b/drivers/spi/spidev.c
> @@ -696,6 +696,7 @@ static struct class *spidev_class;
>  static const struct of_device_id spidev_dt_ids[] = {
>  	{ .compatible = "rohm,dh2228fv" },
>  	{ .compatible = "lineartechnology,ltc2488" },
> +	{ .compatible = "spidev" },
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, spidev_dt_ids);
> -- 
> 2.7.4
>