drivers/pps/clients/pps_parport.c

Source file repositories/reference/linux-study-clean/drivers/pps/clients/pps_parport.c

File Facts

System
Linux kernel
Corpus path
drivers/pps/clients/pps_parport.c
Extension
.c
Size
5661 bytes
Lines
229
Domain
Driver Families
Bucket
drivers/pps
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 pps_client_pp {
	struct pardevice *pardev;	/* parport device */
	struct pps_device *pps;		/* PPS device */
	unsigned int cw;		/* port clear timeout */
	unsigned int cw_err;		/* number of timeouts */
	int index;			/* device number */
};

static inline int signal_is_set(struct parport *port)
{
	return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0;
}

/* parport interrupt handler */
static void parport_irq(void *handle)
{
	struct pps_event_time ts_assert, ts_clear;
	struct pps_client_pp *dev = handle;
	struct parport *port = dev->pardev->port;
	unsigned int i;
	unsigned long flags;

	/* first of all we get the time stamp... */
	pps_get_ts(&ts_assert);

	if (dev->cw == 0)
		/* clear edge capture disabled */
		goto out_assert;

	/* try capture the clear edge */

	/* We have to disable interrupts here. The idea is to prevent
	 * other interrupts on the same processor to introduce random
	 * lags while polling the port. Reading from IO port is known
	 * to take approximately 1us while other interrupt handlers can
	 * take much more potentially.
	 *
	 * Interrupts won't be disabled for a long time because the
	 * number of polls is limited by clear_wait parameter which is
	 * kept rather low. So it should never be an issue.
	 */
	local_irq_save(flags);
	/* check the signal (no signal means the pulse is lost this time) */
	if (!signal_is_set(port)) {
		local_irq_restore(flags);
		dev_err(&dev->pps->dev, "lost the signal\n");
		goto out_assert;
	}

	/* poll the port until the signal is unset */
	for (i = dev->cw; i; i--)
		if (!signal_is_set(port)) {
			pps_get_ts(&ts_clear);
			local_irq_restore(flags);
			dev->cw_err = 0;
			goto out_both;
		}
	local_irq_restore(flags);

	/* timeout */
	dev->cw_err++;
	if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
		dev_err(&dev->pps->dev, "disabled clear edge capture after %d"
				" timeouts\n", dev->cw_err);
		dev->cw = 0;
		dev->cw_err = 0;
	}

out_assert:
	/* fire assert event */
	pps_event(dev->pps, &ts_assert,
			PPS_CAPTUREASSERT, NULL);
	return;

out_both:
	/* fire assert event */
	pps_event(dev->pps, &ts_assert,
			PPS_CAPTUREASSERT, NULL);
	/* fire clear event */
	pps_event(dev->pps, &ts_clear,
			PPS_CAPTURECLEAR, NULL);
	return;
}

static void parport_attach(struct parport *port)
{
	struct pardev_cb pps_client_cb;
	int index;
	struct pps_client_pp *device;
	struct pps_source_info info = {

Annotation

Implementation Notes