drivers/gpio/gpio-gw-pld.c

Source file repositories/reference/linux-study-clean/drivers/gpio/gpio-gw-pld.c

File Facts

System
Linux kernel
Corpus path
drivers/gpio/gpio-gw-pld.c
Extension
.c
Size
3197 bytes
Lines
136
Domain
Driver Families
Bucket
drivers/gpio
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct gw_pld {
	struct gpio_chip chip;
	struct i2c_client *client;
	u8 out;
};

/*
 * The Gateworks I2C PLD chip only expose one read and one write register.
 * Writing a "one" bit (to match the reset state) lets that pin be used as an
 * input. It is an open-drain model.
 */
static int gw_pld_input8(struct gpio_chip *gc, unsigned offset)
{
	struct gw_pld *gw = gpiochip_get_data(gc);

	gw->out |= BIT(offset);
	return i2c_smbus_write_byte(gw->client, gw->out);
}

static int gw_pld_get8(struct gpio_chip *gc, unsigned offset)
{
	struct gw_pld *gw = gpiochip_get_data(gc);
	s32 val;

	val = i2c_smbus_read_byte(gw->client);

	return (val < 0) ? 0 : !!(val & BIT(offset));
}

static int gw_pld_output8(struct gpio_chip *gc, unsigned offset, int value)
{
	struct gw_pld *gw = gpiochip_get_data(gc);

	if (value)
		gw->out |= BIT(offset);
	else
		gw->out &= ~BIT(offset);

	return i2c_smbus_write_byte(gw->client, gw->out);
}

static int gw_pld_set8(struct gpio_chip *gc, unsigned int offset, int value)
{
	return gw_pld_output8(gc, offset, value);
}

static int gw_pld_probe(struct i2c_client *client)
{
	struct device *dev = &client->dev;
	struct gw_pld *gw;
	int ret;

	gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL);
	if (!gw)
		return -ENOMEM;

	gw->chip.base = -1;
	gw->chip.can_sleep = true;
	gw->chip.parent = dev;
	gw->chip.owner = THIS_MODULE;
	gw->chip.label = dev_name(dev);
	gw->chip.ngpio = 8;
	gw->chip.direction_input = gw_pld_input8;
	gw->chip.get = gw_pld_get8;
	gw->chip.direction_output = gw_pld_output8;
	gw->chip.set = gw_pld_set8;
	gw->client = client;

	/*
	 * The Gateworks I2C PLD chip does not properly send the acknowledge
	 * bit at all times, but we can still use the standard i2c_smbus
	 * functions by simply ignoring this bit.
	 */
	client->flags |= I2C_M_IGNORE_NAK;
	gw->out = 0xFF;

	i2c_set_clientdata(client, gw);

	ret = devm_gpiochip_add_data(dev, &gw->chip, gw);
	if (ret)
		return ret;

	dev_info(dev, "registered Gateworks PLD GPIO device\n");

	return 0;
}

static const struct i2c_device_id gw_pld_id[] = {
	{ .name = "gw-pld" },
	{ }

Annotation

Implementation Notes