drivers/siox/siox-bus-gpio.c

Source file repositories/reference/linux-study-clean/drivers/siox/siox-bus-gpio.c

File Facts

System
Linux kernel
Corpus path
drivers/siox/siox-bus-gpio.c
Extension
.c
Size
3963 bytes
Lines
153
Domain
Driver Families
Bucket
drivers/siox
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 siox_gpio_ddata {
	struct gpio_desc *din;
	struct gpio_desc *dout;
	struct gpio_desc *dclk;
	struct gpio_desc *dld;
};

static unsigned int siox_clkhigh_ns = 1000;
static unsigned int siox_loadhigh_ns;
static unsigned int siox_bytegap_ns;

static int siox_gpio_pushpull(struct siox_master *smaster,
			      size_t setbuf_len, const u8 setbuf[],
			      size_t getbuf_len, u8 getbuf[])
{
	struct siox_gpio_ddata *ddata = siox_master_get_devdata(smaster);
	size_t i;
	size_t cycles = max(setbuf_len, getbuf_len);

	/* reset data and clock */
	gpiod_set_value_cansleep(ddata->dout, 0);
	gpiod_set_value_cansleep(ddata->dclk, 0);

	gpiod_set_value_cansleep(ddata->dld, 1);
	ndelay(siox_loadhigh_ns);
	gpiod_set_value_cansleep(ddata->dld, 0);

	for (i = 0; i < cycles; ++i) {
		u8 set = 0, get = 0;
		size_t j;

		if (i >= cycles - setbuf_len)
			set = setbuf[i - (cycles - setbuf_len)];

		for (j = 0; j < 8; ++j) {
			get <<= 1;
			if (gpiod_get_value_cansleep(ddata->din))
				get |= 1;

			/* DOUT is logically inverted */
			gpiod_set_value_cansleep(ddata->dout, !(set & 0x80));
			set <<= 1;

			gpiod_set_value_cansleep(ddata->dclk, 1);
			ndelay(siox_clkhigh_ns);
			gpiod_set_value_cansleep(ddata->dclk, 0);
		}

		if (i < getbuf_len)
			getbuf[i] = get;

		ndelay(siox_bytegap_ns);
	}

	gpiod_set_value_cansleep(ddata->dld, 1);
	ndelay(siox_loadhigh_ns);
	gpiod_set_value_cansleep(ddata->dld, 0);

	/*
	 * Resetting dout isn't necessary protocol wise, but it makes the
	 * signals more pretty because the dout level is deterministic between
	 * cycles. Note that this only affects dout between the master and the
	 * first siox device. dout for the later devices depend on the output of
	 * the previous siox device.
	 */
	gpiod_set_value_cansleep(ddata->dout, 0);

	return 0;
}

static int siox_gpio_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct siox_gpio_ddata *ddata;
	int ret;
	struct siox_master *smaster;

	smaster = devm_siox_master_alloc(dev, sizeof(*ddata));
	if (!smaster)
		return -ENOMEM;

	platform_set_drvdata(pdev, smaster);
	ddata = siox_master_get_devdata(smaster);

	ddata->din = devm_gpiod_get(dev, "din", GPIOD_IN);
	if (IS_ERR(ddata->din))
		return dev_err_probe(dev, PTR_ERR(ddata->din),
				     "Failed to get din GPIO\n");

	ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW);

Annotation

Implementation Notes