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Date: Wed, 23 Feb 2011 01:12:33 +0000
From: Ben Dooks <ben-i2c@fluff.org>
To: Thomas Chou <thomas@wytron.com.tw>
Cc: Grant Likely <grant.likely@secretlab.ca>, Ben Dooks <ben-linux@fluff.org>,
        linux-kernel@vger.kernel.org, nios2-dev@sopc.et.ntust.edu.tw,
        devicetree-discuss@lists.ozlabs.org, linux-i2c@vger.kernel.org,
        Albert Herranz <albert_herranz@yahoo.es>
Subject: Re: [PATCH v5] i2c-gpio: add devicetree support
Message-ID: <20110223011232.GC15795@trinity.fluff.org>
References: <1297304967-3759-1-git-send-email-thomas@wytron.com.tw> <1297650610-12400-1-git-send-email-thomas@wytron.com.tw>
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On Mon, Feb 14, 2011 at 10:30:10AM +0800, Thomas Chou wrote:
> From: Albert Herranz <albert_herranz@yahoo.es>
> 
> This patch adds devicetree support to i2c-gpio driver. The allocation
> of local data is integrated to a private structure, and use devm_*
> helper for easy cleanup.
> 
> It is base on an earlier patch for gc-linux from
> Albert Herranz <albert_herranz@yahoo.es>.
> 
> Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
> CC: Albert Herranz <albert_herranz@yahoo.es>
> Acked-by: Haavard Skinnemoen <hskinnemoen@gmail.com>
> ---
> for v2.6.39
> v2 move of nodes probing to a hook, which will be optimized out
>      when devicetree is not used.
>    use linux/gpio.h.
>    move binding doc to i2c/i2c-gpio.txt.
> v3 use speed-hz instead of udelay in dts binding.
>    condition the devicetree probe.
> v4 simplify private allocation.
> v5 condition module device table export for of.
> 
>  Documentation/devicetree/bindings/i2c/i2c-gpio.txt |   40 +++++++
>  drivers/i2c/busses/i2c-gpio.c                      |  113 ++++++++++++++++----
>  2 files changed, 133 insertions(+), 20 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/i2c/i2c-gpio.txt
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-gpio.txt b/Documentation/devicetree/bindings/i2c/i2c-gpio.txt
> new file mode 100644
> index 0000000..38ef4f2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/i2c-gpio.txt
> @@ -0,0 +1,40 @@
> +GPIO-based I2C
> +
> +Required properties:
> +- compatible : should be "i2c-gpio".
> +- gpios : should specify GPIOs used for SDA and SCL lines, in that order.
> +Optional properties:
> +- sda-is-open-drain : present if SDA gpio is open-drain.
> +- scl-is-open-drain : present if SCL gpio is open-drain.
> +- scl-is-output-only : present if the output driver for SCL cannot be
> +	turned off. this will prevent clock stretching from working.
> +- speed-hz : SCL frequency.
> +- timeout : clock stretching timeout in milliseconds.
> +
> +Example:
> +
> +gpio0: starlet-gpio@0d8000c0 {
> +	compatible = "nintendo,starlet-gpio";
> +	reg = <0d8000c0 4>;
> +	gpio-controller;
> +	#gpio-cells = <2>;
> +};
> +
> +i2c-video {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	compatible = "i2c-gpio";
> +
> +	gpios = <&gpio0 10 0	/* SDA line */
> +		 &gpio0 11 0	/* SCL line */
> +		>;
> +	sda-is-open-drain;
> +	scl-is-open-drain;
> +	scl-is-output-only;
> +	speed-hz = <250000>;
> +
> +	audio-video-encoder {
> +		compatible = "nintendo,wii-ave-rvl";
> +		reg = <70>;
> +	};
> +};
> diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c
> index d9aa9a6..6cc5f15 100644
> --- a/drivers/i2c/busses/i2c-gpio.c
> +++ b/drivers/i2c/busses/i2c-gpio.c
> @@ -14,8 +14,14 @@
>  #include <linux/module.h>
>  #include <linux/slab.h>
>  #include <linux/platform_device.h>
> +#include <linux/gpio.h>
> +#include <linux/of_i2c.h>
>  
> -#include <asm/gpio.h>
> +struct i2c_gpio_private_data {
> +	struct i2c_adapter adap;
> +	struct i2c_algo_bit_data bit_data;
> +	struct i2c_gpio_platform_data pdata;
> +};
>  
>  /* Toggle SDA by changing the direction of the pin */
>  static void i2c_gpio_setsda_dir(void *data, int state)
> @@ -78,24 +84,80 @@ static int i2c_gpio_getscl(void *data)
>  	return gpio_get_value(pdata->scl_pin);
>  }
>  
> +#ifdef CONFIG_OF
> +#include <linux/of_gpio.h>
> +
> +/* Check if devicetree nodes exist and build platform data */
> +static int i2c_gpio_of_probe(struct platform_device *pdev,
> +			     struct i2c_gpio_platform_data *pdata)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	const __be32 *prop;
> +	int sda_pin, scl_pin;
> +	int len;
> +
> +	if (!np || of_gpio_count(np) < 2)
> +		return -ENXIO;

Would prefer to see different return code, most bus probe functions
tend to drop these without signalling to the user as they assume the
device was either never there or totally faulty.

> +	sda_pin = of_get_gpio_flags(np, 0, NULL);
> +	scl_pin = of_get_gpio_flags(np, 1, NULL);
> +	if (sda_pin < 0 || scl_pin < 0) {
> +		pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
> +		       np->full_name, sda_pin, scl_pin);
> +		return -ENXIO;
> +	}

see same as above.

> +	pdata->sda_pin = sda_pin;
> +	pdata->scl_pin = scl_pin;
> +	prop = of_get_property(np, "sda-is-open-drain", NULL);
> +	if (prop)
> +		pdata->sda_is_open_drain = 1;
> +	prop = of_get_property(np, "scl-is-open-drain", NULL);
> +	if (prop)
> +		pdata->scl_is_open_drain = 1;
> +	prop = of_get_property(np, "scl-is-output-only", NULL);
> +	if (prop)
> +		pdata->scl_is_output_only = 1;
> +	prop = of_get_property(np, "speed-hz", &len);
> +	if (prop && len >= sizeof(__be32))
> +		pdata->udelay = DIV_ROUND_UP(1000000, be32_to_cpup(prop) * 2);
> +	prop = of_get_property(np, "timeout", &len);
> +	if (prop && len >= sizeof(__be32))
> +		pdata->timeout = msecs_to_jiffies(be32_to_cpup(prop));
> +
> +	return 0;
> +}
> +#else
> +static int i2c_gpio_of_probe(struct platform_device *pdev,
> +			     struct i2c_gpio_platform_data *pdata)
> +{
> +	return -ENXIO;
> +}

might be valid here, however can we make this NULL if no support?

> +#endif
> +
>  static int __devinit i2c_gpio_probe(struct platform_device *pdev)
>  {
> +	struct i2c_gpio_private_data *priv;
>  	struct i2c_gpio_platform_data *pdata;
>  	struct i2c_algo_bit_data *bit_data;
>  	struct i2c_adapter *adap;
>  	int ret;
>  
> -	pdata = pdev->dev.platform_data;
> -	if (!pdata)
> -		return -ENXIO;
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +	adap = &priv->adap;
> +	bit_data = &priv->bit_data;
> +	pdata = &priv->pdata;
>  
> -	ret = -ENOMEM;
> -	adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
> -	if (!adap)
> -		goto err_alloc_adap;
> -	bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
> -	if (!bit_data)
> -		goto err_alloc_bit_data;
> +	if (pdev->dev.platform_data) {
> +		*pdata = *(struct i2c_gpio_platform_data *)
> +			pdev->dev.platform_data;
> +	} else {
> +		ret = i2c_gpio_of_probe(pdev, pdata);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	ret = gpio_request(pdata->sda_pin, "sda");
>  	if (ret)
> @@ -143,6 +205,7 @@ static int __devinit i2c_gpio_probe(struct platform_device *pdev)
>  	adap->algo_data = bit_data;
>  	adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
>  	adap->dev.parent = &pdev->dev;
> +	adap->dev.of_node = pdev->dev.of_node;
>  
>  	/*
>  	 * If "dev->id" is negative we consider it as zero.
> @@ -154,13 +217,16 @@ static int __devinit i2c_gpio_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto err_add_bus;
>  
> -	platform_set_drvdata(pdev, adap);
> +	platform_set_drvdata(pdev, priv);
>  
>  	dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
>  		 pdata->sda_pin, pdata->scl_pin,
>  		 pdata->scl_is_output_only
>  		 ? ", no clock stretching" : "");
>  
> +	/* Now register all the child nodes */
> +	of_i2c_register_devices(adap);
> +
>  	return 0;
>  
>  err_add_bus:
> @@ -168,34 +234,41 @@ err_add_bus:
>  err_request_scl:
>  	gpio_free(pdata->sda_pin);
>  err_request_sda:
> -	kfree(bit_data);
> -err_alloc_bit_data:
> -	kfree(adap);
> -err_alloc_adap:
>  	return ret;
>  }
>  
>  static int __devexit i2c_gpio_remove(struct platform_device *pdev)
>  {
> +	struct i2c_gpio_private_data *priv;
>  	struct i2c_gpio_platform_data *pdata;
>  	struct i2c_adapter *adap;
>  
> -	adap = platform_get_drvdata(pdev);
> -	pdata = pdev->dev.platform_data;
> +	priv = platform_get_drvdata(pdev);
> +	adap = &priv->adap;
> +	pdata = &priv->pdata;
>  
>  	i2c_del_adapter(adap);
>  	gpio_free(pdata->scl_pin);
>  	gpio_free(pdata->sda_pin);
> -	kfree(adap->algo_data);
> -	kfree(adap);
>  
>  	return 0;
>  }
>  
> +#ifdef CONFIG_OF
> +static const struct of_device_id i2c_gpio_match[] = {
> +	{ .compatible = "i2c-gpio", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, i2c_gpio_match);
> +#else /* CONFIG_OF */
> +#define i2c_gpio_match NULL
> +#endif /* CONFIG_OF */
> +
>  static struct platform_driver i2c_gpio_driver = {
>  	.driver		= {
>  		.name	= "i2c-gpio",
>  		.owner	= THIS_MODULE,
> +		.of_match_table = i2c_gpio_match,
>  	},
>  	.probe		= i2c_gpio_probe,
>  	.remove		= __devexit_p(i2c_gpio_remove),
> -- 
> 1.7.4
> 
> --
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-- 
Ben Dooks, ben@fluff.org, http://www.fluff.org/ben/

Large Hadron Colada: A large Pina Colada that makes the universe disappear.

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