linux-kernel - Re: [PATCH 1/3] i2c: Provide 'device type' to 'OF device node' look-up

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Message-ID: <20140602135722.GC4146@lee--X1>
Date:	Mon, 2 Jun 2014 14:57:22 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	wsa@...-dreams.de
Cc:	linus.walleij@...aro.org, grant.likely@...aro.org,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH 1/3] i2c: Provide 'device type' to 'OF device node'
 look-up

> We have a problem.  There are lots of I2C device ID tables scattered
> around the kernel which are redundant in all Device Tree and/or ACPI
> only supported device drivers.  After recent discussions it has become
> apparent that the only thing blocking the complete removal of these
> tables is the continued support of 'register an I2C device via sysfs'
> functionality.  As the sysfs method doesn't know anything about Device
> Tree or ACPI, we can not pass any nodes in.  This patch searches all
> known Device Tree nodes and attempts to acquire a match from the
> device name provided via sysfs.  It can not fail, but if found assigns
> the matching of_node to i2c_board_info prior to registering.
> 
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  drivers/i2c/i2c-core.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)

[...]

> +static struct device_node *of_i2c_type_to_node(char *type)
> +{
> +	struct device_node *np;
> +	const char *compatible, *name;
> +	int len;
> +
> +	if (!type)
> +		return NULL;
> +
> +	for_each_of_allnodes(np) {
> +		compatible = of_get_property(np, "compatible", &len);
> +		if (!compatible)
> +			continue;
> +
> +		name = strchr(compatible, ',');
> +		if (!name)
> +			name = compatible;
> +		else
> +			name++;
> +
> +		if (!strncmp(name, type, len - (name - compatible)))
> +			return np;
> +	}
> +
> +	return NULL;
> +}

Ah, this _might_ not work if there are more than one devices of the
same type.  I guess I need to check the 'reg' property too.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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