drivers/char/hw_random/timeriomem-rng.c

Source file repositories/reference/linux-study-clean/drivers/char/hw_random/timeriomem-rng.c

File Facts

System
Linux kernel
Corpus path
drivers/char/hw_random/timeriomem-rng.c
Extension
.c
Size
5338 bytes
Lines
203
Domain
Driver Families
Bucket
drivers/char
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 timeriomem_rng_private {
	void __iomem		*io_base;
	ktime_t			period;
	unsigned int		present:1;

	struct hrtimer		timer;
	struct completion	completion;

	struct hwrng		rng_ops;
};

static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
				size_t max, bool wait)
{
	struct timeriomem_rng_private *priv =
		container_of(hwrng, struct timeriomem_rng_private, rng_ops);
	int retval = 0;
	int period_us = ktime_to_us(priv->period);

	/*
	 * There may not have been enough time for new data to be generated
	 * since the last request.  If the caller doesn't want to wait, let them
	 * bail out.  Otherwise, wait for the completion.  If the new data has
	 * already been generated, the completion should already be available.
	 */
	if (!wait && !priv->present)
		return 0;

	wait_for_completion(&priv->completion);

	do {
		/*
		 * After the first read, all additional reads will need to wait
		 * for the RNG to generate new data.  Since the period can have
		 * a wide range of values (1us to 1s have been observed), allow
		 * for 1% tolerance in the sleep time rather than a fixed value.
		 */
		if (retval > 0)
			usleep_range(period_us,
					period_us + max(1, period_us / 100));

		*(u32 *)data = readl(priv->io_base);
		retval += sizeof(u32);
		data += sizeof(u32);
		max -= sizeof(u32);
	} while (wait && max > sizeof(u32));

	/*
	 * Block any new callers until the RNG has had time to generate new
	 * data.
	 */
	priv->present = 0;
	reinit_completion(&priv->completion);
	hrtimer_forward_now(&priv->timer, priv->period);
	hrtimer_restart(&priv->timer);

	return retval;
}

static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer)
{
	struct timeriomem_rng_private *priv
		= container_of(timer, struct timeriomem_rng_private, timer);

	priv->present = 1;
	complete(&priv->completion);

	return HRTIMER_NORESTART;
}

static int timeriomem_rng_probe(struct platform_device *pdev)
{
	struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
	struct timeriomem_rng_private *priv;
	struct resource *res;
	int err = 0;
	int period;

	if (!pdev->dev.of_node && !pdata) {
		dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
		return -EINVAL;
	}

	/* Allocate memory for the device structure (and zero it) */
	priv = devm_kzalloc(&pdev->dev,
			sizeof(struct timeriomem_rng_private), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	platform_set_drvdata(pdev, priv);

Annotation

Implementation Notes