drivers/char/hpet.c

Source file repositories/reference/linux-study-clean/drivers/char/hpet.c

File Facts

System
Linux kernel
Corpus path
drivers/char/hpet.c
Extension
.c
Size
24000 bytes
Lines
1042
Domain
Driver Families
Bucket
drivers/char
Inferred role
Driver Families: operation-table or driver-model contract
Status
pattern 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

static const struct file_operations hpet_fops = {
	.owner = THIS_MODULE,
	.read = hpet_read,
	.poll = hpet_poll,
	.unlocked_ioctl = hpet_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl = hpet_compat_ioctl,
#endif
	.open = hpet_open,
	.release = hpet_release,
	.fasync = hpet_fasync,
	.mmap_prepare = hpet_mmap_prepare,
};

static int hpet_is_known(struct hpet_data *hdp)
{
	struct hpets *hpetp;

	for (hpetp = hpets; hpetp; hpetp = hpetp->hp_next)
		if (hpetp->hp_hpet_phys == hdp->hd_phys_address)
			return 1;

	return 0;
}

static const struct ctl_table hpet_table[] = {
	{
	 .procname = "max-user-freq",
	 .data = &hpet_max_freq,
	 .maxlen = sizeof(int),
	 .mode = 0644,
	 .proc_handler = proc_dointvec,
	 },
};

static struct ctl_table_header *sysctl_header;

/*
 * Adjustment for when arming the timer with
 * initial conditions.  That is, main counter
 * ticks expired before interrupts are enabled.
 */
#define	TICK_CALIBRATE	(1000UL)

static unsigned long __hpet_calibrate(struct hpets *hpetp)
{
	struct hpet_timer __iomem *timer = NULL;
	unsigned long t, m, count, i, flags, start;
	struct hpet_dev *devp;
	int j;
	struct hpet __iomem *hpet;

	for (j = 0, devp = hpetp->hp_dev; j < hpetp->hp_ntimer; j++, devp++)
		if ((devp->hd_flags & HPET_OPEN) == 0) {
			timer = devp->hd_timer;
			break;
		}

	if (!timer)
		return 0;

	hpet = hpetp->hp_hpet;
	t = read_counter(&timer->hpet_compare);

	i = 0;
	count = hpet_time_div(hpetp, TICK_CALIBRATE);

	local_irq_save(flags);

	start = read_counter(&hpet->hpet_mc);

	do {
		m = read_counter(&hpet->hpet_mc);
		write_counter(t + m + hpetp->hp_delta, &timer->hpet_compare);
	} while (i++, (m - start) < count);

	local_irq_restore(flags);

	return (m - start) / i;
}

static unsigned long hpet_calibrate(struct hpets *hpetp)
{
	unsigned long ret = ~0UL;
	unsigned long tmp;

	/*
	 * Try to calibrate until return value becomes stable small value.
	 * If SMI interruption occurs in calibration loop, the return value
	 * will be big. This avoids its impact.

Annotation

Implementation Notes