[PATCH 2/4] thunderbolt: Add tb_ring_poll_pending()

[Mika Westerberg <mika.westerberg@linux.intel.com>]

This helper can be used to figure out whether tb_ring_poll() has a frame
to be returned. This can be used without the caller needing to take its
own lock.

Assisted-by: LLM
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/thunderbolt/nhi.c   | 19 +++++++++++++++++++
 include/linux/thunderbolt.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index 371ee155d98f..020db5a1f029 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -455,6 +455,25 @@ struct ring_frame *tb_ring_poll(struct tb_ring *ring)
 }
 EXPORT_SYMBOL_GPL(tb_ring_poll);
 
+/**
+ * tb_ring_poll_pending() - Does the ring have completed frame
+ * @ring: Ring to check
+ *
+ * Can be used to check whether there is a completed frame in the ring
+ * that next call to tb_ring_poll() returns.
+ *
+ * Return: %true if a completed frame is waiting, %false otherwise.
+ */
+bool tb_ring_poll_pending(struct tb_ring *ring)
+{
+	guard(spinlock_irqsave)(&ring->lock);
+
+	if (!ring->running || ring_empty(ring))
+		return false;
+	return !!(ring->descriptors[ring->tail].flags & RING_DESC_COMPLETED);
+}
+EXPORT_SYMBOL_GPL(tb_ring_poll_pending);
+
 static void __ring_interrupt_mask(struct tb_ring *ring, bool mask)
 {
 	int interrupt_index = ring_interrupt_index(ring);
diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h
index 8ca941e8b5d0..779381ebeea2 100644
--- a/include/linux/thunderbolt.h
+++ b/include/linux/thunderbolt.h
@@ -757,6 +757,7 @@ static inline int tb_ring_tx_more(struct tb_ring *ring, struct ring_frame *frame
 
 /* Used only when the ring is in polling mode */
 struct ring_frame *tb_ring_poll(struct tb_ring *ring);
+bool tb_ring_poll_pending(struct tb_ring *ring);
 void tb_ring_poll_complete(struct tb_ring *ring);
 
 int tb_ring_throttling(struct tb_ring *ring, unsigned int interval_nsec);
-- 
2.50.1