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Juergen Beiserttorvalds
Juergen Beisert
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torvalds
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gpio: gpio driver for max7301 SPI GPIO expander
Maxim's MAX7301 is an SPI GPIO expander with 28 GPIOs. Note: MAX7301's interrupt feature is not supported yet. [akpm@linux-foundation.org: coding-style fixes] [g.liakhovetski@pengutronix.de: Fix inaccuracies in comments, check spi_setup() return code, mask off high byte in max7301_read()] Signed-off-by: Juergen Beisert <j.beisert@pengutronix.de> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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‎drivers/gpio/Kconfig

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@@ -69,6 +69,12 @@ config GPIO_PCF857X
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comment "SPI GPIO expanders:"
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config GPIO_MAX7301
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tristate "Maxim MAX7301 GPIO expander"
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depends on SPI_MASTER
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help
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gpio driver for Maxim MAX7301 SPI GPIO expander.
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config GPIO_MCP23S08
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tristate "Microchip MCP23S08 I/O expander"
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depends on SPI_MASTER

‎drivers/gpio/Makefile

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@@ -4,6 +4,7 @@ ccflags-$(CONFIG_DEBUG_GPIO) += -DDEBUG
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obj-$(CONFIG_HAVE_GPIO_LIB) += gpiolib.o
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obj-$(CONFIG_GPIO_MAX7301) += max7301.o
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obj-$(CONFIG_GPIO_MCP23S08) += mcp23s08.o
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obj-$(CONFIG_GPIO_PCA953X) += pca953x.o
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obj-$(CONFIG_GPIO_PCF857X) += pcf857x.o

‎drivers/gpio/max7301.c

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/**
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* drivers/gpio/max7301.c
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*
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* Copyright (C) 2006 Juergen Beisert, Pengutronix
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* Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* The Maxim's MAX7301 device is an SPI driven GPIO expander. There are
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* 28 GPIOs. 8 of them can trigger an interrupt. See datasheet for more
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* details
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* Note:
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* - DIN must be stable at the rising edge of clock.
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* - when writing:
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* - always clock in 16 clocks at once
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* - at DIN: D15 first, D0 last
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* - D0..D7 = databyte, D8..D14 = commandbyte
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* - D15 = low -> write command
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* - when reading
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* - always clock in 16 clocks at once
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* - at DIN: D15 first, D0 last
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* - D0..D7 = dummy, D8..D14 = register address
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* - D15 = high -> read command
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* - raise CS and assert it again
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* - always clock in 16 clocks at once
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* - at DOUT: D15 first, D0 last
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* - D0..D7 contains the data from the first cycle
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*
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* The driver exports a standard gpiochip interface
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*/
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#include <linux/init.h>
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#include <linux/platform_device.h>
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#include <linux/mutex.h>
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#include <linux/spi/spi.h>
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#include <linux/spi/max7301.h>
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#include <linux/gpio.h>
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#define DRIVER_NAME "max7301"
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/*
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* Pin configurations, see MAX7301 datasheet page 6
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*/
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#define PIN_CONFIG_MASK 0x03
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#define PIN_CONFIG_IN_PULLUP 0x03
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#define PIN_CONFIG_IN_WO_PULLUP 0x02
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#define PIN_CONFIG_OUT 0x01
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#define PIN_NUMBER 28
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/*
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* Some registers must be read back to modify.
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* To save time we cache them here in memory
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*/
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struct max7301 {
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struct mutex lock;
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u8 port_config[8]; /* field 0 is unused */
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u32 out_level; /* cached output levels */
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struct gpio_chip chip;
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struct spi_device *spi;
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};
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/**
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* max7301_write - Write a new register content
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* @spi: The SPI device
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* @reg: Register offset
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* @val: Value to write
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*
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* A write to the MAX7301 means one message with one transfer
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*
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* Returns 0 if successful or a negative value on error
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*/
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static int max7301_write(struct spi_device *spi, unsigned int reg, unsigned int val)
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{
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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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}
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/**
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* max7301_read - Read back register content
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* @spi: The SPI device
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* @reg: Register offset
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*
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* A read from the MAX7301 means two transfers; here, one message each
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*
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* Returns positive 8 bit value from device if successful or a
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* negative value on error
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*/
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static int max7301_read(struct spi_device *spi, unsigned int reg)
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{
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int ret;
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u16 word;
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word = 0x8000 | (reg << 8);
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ret = spi_write(spi, (const u8 *)&word, sizeof(word));
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if (ret)
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return ret;
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/*
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* This relies on the fact, that a transfer with NULL tx_buf shifts out
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* zero bytes (=NOOP for MAX7301)
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*/
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ret = spi_read(spi, (u8 *)&word, sizeof(word));
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if (ret)
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return ret;
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return word & 0xff;
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}
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static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
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{
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struct max7301 *ts = container_of(chip, struct max7301, chip);
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u8 *config;
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int ret;
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/* First 4 pins are unused in the controller */
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offset += 4;
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config = &ts->port_config[offset >> 2];
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mutex_lock(&ts->lock);
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/* Standard GPIO API doesn't support pull-ups, has to be extended.
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* Hard-coding no pollup for now. */
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*config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
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ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
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mutex_unlock(&ts->lock);
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return ret;
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}
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static int __max7301_set(struct max7301 *ts, unsigned offset, int value)
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{
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if (value) {
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ts->out_level |= 1 << offset;
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return max7301_write(ts->spi, 0x20 + offset, 0x01);
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} else {
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ts->out_level &= ~(1 << offset);
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return max7301_write(ts->spi, 0x20 + offset, 0x00);
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}
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}
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static int max7301_direction_output(struct gpio_chip *chip, unsigned offset,
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int value)
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{
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struct max7301 *ts = container_of(chip, struct max7301, chip);
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u8 *config;
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int ret;
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/* First 4 pins are unused in the controller */
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offset += 4;
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config = &ts->port_config[offset >> 2];
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mutex_lock(&ts->lock);
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*config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
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ret = __max7301_set(ts, offset, value);
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if (!ret)
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ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
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mutex_unlock(&ts->lock);
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return ret;
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}
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static int max7301_get(struct gpio_chip *chip, unsigned offset)
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{
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struct max7301 *ts = container_of(chip, struct max7301, chip);
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int config, level = -EINVAL;
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/* First 4 pins are unused in the controller */
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offset += 4;
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mutex_lock(&ts->lock);
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config = (ts->port_config[offset >> 2] >> ((offset & 3) * 2)) & 3;
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switch (config) {
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case 1:
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/* Output: return cached level */
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level = !!(ts->out_level & (1 << offset));
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break;
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case 2:
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case 3:
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/* Input: read out */
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level = max7301_read(ts->spi, 0x20 + offset) & 0x01;
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}
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mutex_unlock(&ts->lock);
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return level;
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}
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static void max7301_set(struct gpio_chip *chip, unsigned offset, int value)
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{
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struct max7301 *ts = container_of(chip, struct max7301, chip);
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/* First 4 pins are unused in the controller */
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offset += 4;
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mutex_lock(&ts->lock);
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__max7301_set(ts, offset, value);
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mutex_unlock(&ts->lock);
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}
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static int __devinit max7301_probe(struct spi_device *spi)
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{
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struct max7301 *ts;
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struct max7301_platform_data *pdata;
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int i, ret;
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pdata = spi->dev.platform_data;
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if (!pdata || !pdata->base)
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return -ENODEV;
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/*
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* bits_per_word cannot be configured in platform data
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*/
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spi->bits_per_word = 16;
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ret = spi_setup(spi);
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if (ret < 0)
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return ret;
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ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
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if (!ts)
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return -ENOMEM;
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mutex_init(&ts->lock);
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dev_set_drvdata(&spi->dev, ts);
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/* Power up the chip and disable IRQ output */
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max7301_write(spi, 0x04, 0x01);
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ts->spi = spi;
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ts->chip.label = DRIVER_NAME,
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ts->chip.direction_input = max7301_direction_input;
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ts->chip.get = max7301_get;
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ts->chip.direction_output = max7301_direction_output;
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ts->chip.set = max7301_set;
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ts->chip.base = pdata->base;
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ts->chip.ngpio = PIN_NUMBER;
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ts->chip.can_sleep = 1;
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ts->chip.dev = &spi->dev;
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ts->chip.owner = THIS_MODULE;
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ret = gpiochip_add(&ts->chip);
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if (ret)
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goto exit_destroy;
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/*
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* tristate all pins in hardware and cache the
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* register values for later use.
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*/
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for (i = 1; i < 8; i++) {
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int j;
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/* 0xAA means input with internal pullup disabled */
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max7301_write(spi, 0x08 + i, 0xAA);
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ts->port_config[i] = 0xAA;
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for (j = 0; j < 4; j++) {
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int idx = ts->chip.base + (i - 1) * 4 + j;
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ret = gpio_direction_input(idx);
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if (ret)
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goto exit_remove;
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gpio_free(idx);
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}
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}
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return ret;
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exit_remove:
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gpiochip_remove(&ts->chip);
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exit_destroy:
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dev_set_drvdata(&spi->dev, NULL);
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mutex_destroy(&ts->lock);
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kfree(ts);
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return ret;
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}
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static int max7301_remove(struct spi_device *spi)
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{
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struct max7301 *ts;
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int ret;
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ts = dev_get_drvdata(&spi->dev);
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if (ts == NULL)
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return -ENODEV;
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dev_set_drvdata(&spi->dev, NULL);
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/* Power down the chip and disable IRQ output */
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max7301_write(spi, 0x04, 0x00);
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ret = gpiochip_remove(&ts->chip);
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if (!ret) {
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mutex_destroy(&ts->lock);
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kfree(ts);
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} else
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dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",
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ret);
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return ret;
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}
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static struct spi_driver max7301_driver = {
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.driver = {
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.name = DRIVER_NAME,
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.owner = THIS_MODULE,
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},
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.probe = max7301_probe,
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.remove = __devexit_p(max7301_remove),
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};
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static int __init max7301_init(void)
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{
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return spi_register_driver(&max7301_driver);
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}
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static void __exit max7301_exit(void)
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{
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spi_unregister_driver(&max7301_driver);
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}
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module_init(max7301_init);
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module_exit(max7301_exit);
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MODULE_AUTHOR("Juergen Beisert");
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MODULE_LICENSE("GPL v2");
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MODULE_DESCRIPTION("MAX7301 SPI based GPIO-Expander");

‎include/linux/spi/max7301.h

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#ifndef LINUX_SPI_MAX7301_H
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#define LINUX_SPI_MAX7301_H
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struct max7301_platform_data {
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/* number assigned to the first GPIO */
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unsigned base;
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};
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#endif

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