drivers/gpu/drm/solomon/ssd130x-spi.c

Source file repositories/reference/linux-study-clean/drivers/gpu/drm/solomon/ssd130x-spi.c

File Facts

System
Linux kernel
Corpus path
drivers/gpu/drm/solomon/ssd130x-spi.c
Extension
.c
Size
5034 bytes
Lines
194
Domain
Driver Families
Bucket
drivers/gpu
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 ssd130x_spi_transport {
	struct spi_device *spi;
	struct gpio_desc *dc;
};

/*
 * The regmap bus .write handler, it is just a wrapper around spi_write()
 * but toggling the Data/Command control pin (D/C#). Since for 4-wire SPI
 * a D/C# pin is used, in contrast with I2C where a control byte is sent,
 * prior to every data byte, that contains a bit with the D/C# value.
 *
 * These control bytes are considered registers by the ssd130x core driver
 * and can be used by the ssd130x SPI driver to determine if the data sent
 * is for a command register or for the Graphic Display Data RAM (GDDRAM).
 */
static int ssd130x_spi_write(void *context, const void *data, size_t count)
{
	struct ssd130x_spi_transport *t = context;
	struct spi_device *spi = t->spi;
	const u8 *reg = data;

	if (*reg == SSD13XX_COMMAND)
		gpiod_set_value_cansleep(t->dc, 0);

	if (*reg == SSD13XX_DATA)
		gpiod_set_value_cansleep(t->dc, 1);

	/* Remove control byte since is not used in a 4-wire SPI interface */
	return spi_write(spi, reg + 1, count - 1);
}

/* The ssd130x driver does not read registers but regmap expects a .read */
static int ssd130x_spi_read(void *context, const void *reg, size_t reg_size,
			    void *val, size_t val_size)
{
	return -EOPNOTSUPP;
}

static const struct regmap_config ssd130x_spi_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.write = ssd130x_spi_write,
	.read = ssd130x_spi_read,
	.can_multi_write = true,
};

static int ssd130x_spi_probe(struct spi_device *spi)
{
	struct ssd130x_spi_transport *t;
	struct ssd130x_device *ssd130x;
	struct regmap *regmap;
	struct gpio_desc *dc;
	struct device *dev = &spi->dev;

	dc = devm_gpiod_get(dev, "dc", GPIOD_OUT_LOW);
	if (IS_ERR(dc))
		return dev_err_probe(dev, PTR_ERR(dc),
				     "Failed to get dc gpio\n");

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

	t->spi = spi;
	t->dc = dc;

	regmap = devm_regmap_init(dev, NULL, t, &ssd130x_spi_regmap_config);
	if (IS_ERR(regmap))
		return PTR_ERR(regmap);

	ssd130x = ssd130x_probe(dev, regmap);
	if (IS_ERR(ssd130x))
		return PTR_ERR(ssd130x);

	spi_set_drvdata(spi, ssd130x);

	return 0;
}

static void ssd130x_spi_remove(struct spi_device *spi)
{
	struct ssd130x_device *ssd130x = spi_get_drvdata(spi);

	ssd130x_remove(ssd130x);
}

static void ssd130x_spi_shutdown(struct spi_device *spi)
{
	struct ssd130x_device *ssd130x = spi_get_drvdata(spi);

Annotation

Implementation Notes