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ADP5588 GPIO Linux Driver

Supported Devices

Evaluation Boards



Software configurable features

Source Code


Source Mainlined?
git Yes


Example platform device initialization

For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.

For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.

21 Oct 2010 16:10 · Michael Hennerich

file: include/linux/i2c/adp5588.h

/* line 103 to 172 */
/* Put one of these structures in i2c_board_info platform_data */
#define ADP5588_KEYMAPSIZE	80
#define GPI_PIN_ROW0 97
#define GPI_PIN_ROW1 98
#define GPI_PIN_ROW2 99
#define GPI_PIN_ROW3 100
#define GPI_PIN_ROW4 101
#define GPI_PIN_ROW5 102
#define GPI_PIN_ROW6 103
#define GPI_PIN_ROW7 104
#define GPI_PIN_COL0 105
#define GPI_PIN_COL1 106
#define GPI_PIN_COL2 107
#define GPI_PIN_COL3 108
#define GPI_PIN_COL4 109
#define GPI_PIN_COL5 110
#define GPI_PIN_COL6 111
#define GPI_PIN_COL7 112
#define GPI_PIN_COL8 113
#define GPI_PIN_COL9 114
struct adp5588_gpi_map {
	unsigned short pin;
	unsigned short sw_evt;
struct adp5588_kpad_platform_data {
	int rows;			/* Number of rows */
	int cols;			/* Number of columns */
	const unsigned short *keymap;	/* Pointer to keymap */
	unsigned short keymapsize;	/* Keymap size */
	unsigned repeat:1;		/* Enable key repeat */
	unsigned en_keylock:1;		/* Enable Key Lock feature */
	unsigned short unlock_key1;	/* Unlock Key 1 */
	unsigned short unlock_key2;	/* Unlock Key 2 */
	const struct adp5588_gpi_map *gpimap;
	unsigned short gpimapsize;
	const struct adp5588_gpio_platform_data *gpio_data;
struct i2c_client; /* forward declaration */
struct adp5588_gpio_platform_data {
	int gpio_start;		/* GPIO Chip base # */
	const char *const *names;
	unsigned irq_base;	/* interrupt base # */
	unsigned pullup_dis_mask; /* Pull-Up Disable Mask */
	int	(*setup)(struct i2c_client *client,
				unsigned gpio, unsigned ngpio,
				void *context);
	int	(*teardown)(struct i2c_client *client,
				unsigned gpio, unsigned ngpio,
				void *context);
	void	*context;

file: arch/blackfin/mach-bf537/boards/stamp.c

static struct adp5588_gpio_platform_data adp5588_gpio_data = {
	.gpio_start = 50,
	.pullup_dis_mask = 0,

Declaring I2C devices

Unlike PCI or USB devices, I2C devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each I2C bus segment, and what address these devices are using. For this reason, the kernel code must instantiate I2C devices explicitly. There are different ways to achieve this, depending on the context and requirements. However the most common method is to declare the I2C devices by bus number.

This method is appropriate when the I2C bus is a system bus, as in many embedded systems, wherein each I2C bus has a number which is known in advance. It is thus possible to pre-declare the I2C devices that inhabit this bus. This is done with an array of struct i2c_board_info, which is registered by calling i2c_register_board_info().

So, to enable such a driver one need only edit the board support file by adding an appropriate entry to i2c_board_info.

For more information see: Documentation/i2c/instantiating-devices

21 Oct 2010 16:10 · Michael Hennerich
static struct i2c_board_info __initdata bfin_i2c_board_info[] = {
#if defined(CONFIG_GPIO_ADP5588) || defined(CONFIG_GPIO_ADP5588_MODULE)
		I2C_BOARD_INFO("adp5588-gpio", 0x34),
		.irq = IRQ_PG0,
		.platform_data = (void *)&adp5588_gpio_data,

Adding Linux driver support

Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)

The ADP5588 Driver depends on CONFIG_I2C
IRQ-Chip interrupt controller support is not available in case this driver is build as Module

<code> Device Drivers —> [*] GPIO Support —>

  1. -- GPIO Support

[ ] Debug GPIO calls

  [*]   /sys/class/gpio/... (sysfs interface)
        *** Memory mapped GPIO expanders: ***
  < >   IT8761E GPIO support
        *** I2C GPIO expanders: ***
  < >   Maxim MAX7300 GPIO expander
  < >   MAX7319, MAX7320-7327 I2C Port Expanders
  < >   PCA953x, PCA955x, TCA64xx, and MAX7310 I/O ports
  < >   PCF857x, PCA{85,96}7x, and MAX732[89] I2C GPIO expanders
  [ ]   Semtech SX150x I2C GPIO expander
  < >   GPIO Support for ADP5520 PMIC
  <*>   ADP5588 I2C GPIO expander
  [*]     Interrupt controller support for ADP5588

< /code>

Hardware configuration

There is no dedicated Blackfin STAMP evaluation board for the ADP5588. During test and driver development we used the ADP5588 Demo Mother/Daughter Board.

It can be easily wired to the Blackfin STAMP TWI/I2C header.

BF537-STAMP (P10) TWI/I2C header ADP5588 Daughter Board
PIN Function PIN/Function
2 (+3.3V) VCC

On the ADP5588 Demo Mother Board replace R30 (10kOhm PULL-UP resistor on /INTB strobe) with a 1-3kOhm resistor. The 10kOhm resistor is too weak - Blackfin might see an additional falling edge interrupt on the rising edge of /INTB.

Driver testing

When the driver is loaded, you should see positive output that it found the ADP5588 GPIO device.

root:/> modprobe adp5588-gpio
adp5588-gpio 0-0034: gpios 50..67 on a adp5588-gpio Rev. 4

For more information see also here: linux-kernel:drivers:gpio-sysfs

root:/> echo 67 > /sys/class/gpio/export

root:/> echo low > /sys/class/gpio/gpio67/direction
root:/> echo high > /sys/class/gpio/gpio67/direction

root:/> echo in > /sys/class/gpio/gpio67/direction
root:/> cat /sys/class/gpio/gpio67/value
root:/> cat /sys/class/gpio/gpio67/value

More Information