gpio-max7301.c 2.7 KB
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/*
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 * Copyright (C) 2006 Juergen Beisert, Pengutronix
 * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
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 * Copyright (C) 2009 Wolfram Sang, Pengutronix
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 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
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 * Check max730x.c for further details.
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 */

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#include <linux/module.h>
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#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/spi/spi.h>
#include <linux/spi/max7301.h>

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/* A write to the MAX7301 means one message with one transfer */
static int max7301_spi_write(struct device *dev, unsigned int reg,
				unsigned int val)
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{
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	struct spi_device *spi = to_spi_device(dev);
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	u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
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	return spi_write(spi, (const u8 *)&word, sizeof(word));
}

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/* A read from the MAX7301 means two transfers; here, one message each */

static int max7301_spi_read(struct device *dev, unsigned int reg)
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{
	int ret;
	u16 word;
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	struct spi_device *spi = to_spi_device(dev);
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	word = 0x8000 | (reg << 8);
	ret = spi_write(spi, (const u8 *)&word, sizeof(word));
	if (ret)
		return ret;
	/*
	 * This relies on the fact, that a transfer with NULL tx_buf shifts out
	 * zero bytes (=NOOP for MAX7301)
	 */
	ret = spi_read(spi, (u8 *)&word, sizeof(word));
	if (ret)
		return ret;
	return word & 0xff;
}

static int __devinit max7301_probe(struct spi_device *spi)
{
	struct max7301 *ts;
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	int ret;
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	/* bits_per_word cannot be configured in platform data */
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	spi->bits_per_word = 16;
	ret = spi_setup(spi);
	if (ret < 0)
		return ret;

	ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
	if (!ts)
		return -ENOMEM;

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	ts->read = max7301_spi_read;
	ts->write = max7301_spi_write;
	ts->dev = &spi->dev;
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	ret = __max730x_probe(ts);
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	if (ret)
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		kfree(ts);
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	return ret;
}

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static int __devexit max7301_remove(struct spi_device *spi)
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{
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	return __max730x_remove(&spi->dev);
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}

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static const struct spi_device_id max7301_id[] = {
	{ "max7301", 0 },
	{ }
};
MODULE_DEVICE_TABLE(spi, max7301_id);

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static struct spi_driver max7301_driver = {
	.driver = {
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		.name = "max7301",
		.owner = THIS_MODULE,
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	},
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	.probe = max7301_probe,
	.remove = __devexit_p(max7301_remove),
	.id_table = max7301_id,
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};

static int __init max7301_init(void)
{
	return spi_register_driver(&max7301_driver);
}
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/* register after spi postcore initcall and before
 * subsys initcalls that may rely on these GPIOs
 */
subsys_initcall(max7301_init);
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static void __exit max7301_exit(void)
{
	spi_unregister_driver(&max7301_driver);
}
module_exit(max7301_exit);

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MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
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MODULE_LICENSE("GPL v2");
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MODULE_DESCRIPTION("MAX7301 GPIO-Expander");