Add support for edge detection to lines requested using
GPIO_GET_LINE_IOCTL.
Signed-off-by: Kent Gibson
---
The edge_detector implementation is based on the V1 lineevent implementation.
drivers/gpio/gpiolib-cdev.c | 314 +++-
drivers/gpio/gpiolib.c | 2 +
drivers/gpio/gpiolib.h | 2 +
3 files changed, 317 insertions(+), 1 deletion(-)
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 1f282207fb70..8caebb460557 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -381,11 +381,43 @@ static int linehandle_create(struct gpio_device *gdev,
void __user *ip)
}
#endif /* CONFIG_GPIO_CDEV_V1 */
+/**
+ * struct edge_detector - contains the state of a line edge detector
+ * @line: the corresponding line request
+ * @irq: the interrupt triggered in response to events on this GPIO
+ * @flags: the flags, GPIOLINE_FLAG_V2_EDGE_RISING and/or
+ * GPIOLINE_FLAG_V2_EDGE_FALLING, indicating the edge detection applied
+ * @timestamp: cache for the timestamp storing it between hardirq and IRQ
+ * thread, used to bring the timestamp close to the actual event
+ * @seqno: the seqno for the current edge event in the sequence of events
+ * for the corresponding line request. Ths is drawn from the @line.
+ * @line_seqno: the seqno for the current edge event in the sequence of
+ * events for this line.
+ */
+struct edge_detector {
+ struct line *line;
+ unsigned int irq;
+ u64 flags;
+ /*
+* timestamp and seqno are shared by edge_irq_handler() and
+* edge_irq_thread() which are themselves mutually exclusive.
+*/
+ u64 timestamp;
+ u32 seqno;
+ u32 line_seqno;
+};
+
/**
* struct line - contains the state of a userspace line request
* @gdev: the GPIO device the line request pertains to
* @label: consumer label used to tag descriptors
* @num_descs: the number of descriptors held in the descs array
+ * @wait: wait queue that handles blocking reads of events
+ * @events: KFIFO for the GPIO events
+ * @seqno: the sequence number for edge events generated on all lines in
+ * this line request. Note that this is not used when @num_descs is 1, as
+ * the line_seqno is then the same and is cheaper to calculate.
+ * @edets: an array of edge detectors, of size @num_descs
* @descs: the GPIO descriptors held by this line request, with @num_descs
* elements.
*/
@@ -393,10 +425,147 @@ struct line {
struct gpio_device *gdev;
const char *label;
u32 num_descs;
+ wait_queue_head_t wait;
+ DECLARE_KFIFO_PTR(events, struct gpioline_event);
+ atomic_t seqno;
+ struct edge_detector *edets;
/* descs must be last so it can be dynamically sized */
struct gpio_desc *descs[];
};
+static inline struct gpio_desc *edge_detector_desc(
+ const struct edge_detector *edet)
+{
+ return edet->line->descs[edet - &edet->line->edets[0]];
+}
+
+static irqreturn_t edge_irq_thread(int irq, void *p)
+{
+ struct edge_detector *edet = p;
+ struct line *line = edet->line;
+ struct gpio_desc *desc = edge_detector_desc(edet);
+ struct gpioline_event le;
+ int ret;
+
+ /* Do not leak kernel stack to userspace */
+ memset(&le, 0, sizeof(le));
+
+ /*
+* We may be running from a nested threaded interrupt in which case
+* we didn't get the timestamp from edge_irq_handler().
+*/
+ if (!edet->timestamp) {
+ le.timestamp = ktime_get_ns();
+ if (line->num_descs != 1)
+ edet->seqno = atomic_inc_return(&line->seqno);
+ } else {
+ le.timestamp = edet->timestamp;
+ }
+ edet->timestamp = 0;
+
+ if (edet->flags == (GPIOLINE_FLAG_V2_EDGE_RISING |
+ GPIOLINE_FLAG_V2_EDGE_FALLING)) {
+ int level = gpiod_get_value_cansleep(desc);
+
+ if (level)
+ /* Emit low-to-high event */
+ le.id = GPIOLINE_EVENT_RISING_EDGE;
+ else
+ /* Emit high-to-low event */
+ le.id = GPIOLINE_EVENT_FALLING_EDGE;
+ } else if (edet->flags == GPIOLINE_FLAG_V2_EDGE_RISING) {
+ /* Emit low-to-high event */
+ le.id = GPIOLINE_EVENT_RISING_EDGE;
+ } else if (edet->flags == GPIOLINE_FLAG_V2_EDGE_FALLING) {
+ /* Emit high-to-low event */
+ le.id = GPIOLINE_EVENT_FALLING_EDGE;
+ } else {
+ return IRQ_NONE;
+ }
+ edet->line_seqno++;
+ le.line_seqno = edet->line_seqno;
+ le.seqno = (line->num_descs == 1) ? le.line_seqno : edet->seqno;
+ le.offset = gpio_chip_hwgpio(desc);
+
+ ret = kfifo_in_spinlocked_noirqsave(&line->events, &le,
+ 1, &line->wait.lock);
+ if (ret)
+ w
