linux-kernel - [PATCH 2/9] staging: axis-fifo: Add poll() support

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Message-ID: <20251227212640.3321310-2-ovidiu.panait.oss@gmail.com>
Date: Sat, 27 Dec 2025 23:26:33 +0200
From: Ovidiu Panait <ovidiu.panait.oss@...il.com>
To: gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org,
	linux-staging@...ts.linux.dev
Subject: [PATCH 2/9] staging: axis-fifo: Add poll() support

Implement poll() file operation to allow userspace applications to
wait for FIFO readiness using select()/poll()/epoll().

This replaces the module parameter-based timeouts removed in the
previous commit.

Signed-off-by: Ovidiu Panait <ovidiu.panait.oss@...il.com>
---
 drivers/staging/axis-fifo/axis-fifo.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/axis-fifo/axis-fifo.c b/drivers/staging/axis-fifo/axis-fifo.c
index b2a9f5542fc1..b9b2700410b8 100644
--- a/drivers/staging/axis-fifo/axis-fifo.c
+++ b/drivers/staging/axis-fifo/axis-fifo.c
@@ -32,6 +32,7 @@
 #include <linux/jiffies.h>
 #include <linux/miscdevice.h>
 #include <linux/debugfs.h>
+#include <linux/poll.h>
 
 /* ----------------------------
  *       driver parameters
@@ -345,6 +346,28 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 	return ret;
 }
 
+static __poll_t axis_fifo_poll(struct file *f, poll_table *wait)
+{
+	struct axis_fifo *fifo = f->private_data;
+	__poll_t mask = 0;
+
+	if (fifo->has_rx_fifo) {
+		poll_wait(f, &fifo->read_queue, wait);
+
+		if (ioread32(fifo->base_addr + XLLF_RDFO_OFFSET))
+			mask |= EPOLLIN | EPOLLRDNORM;
+	}
+
+	if (fifo->has_tx_fifo) {
+		poll_wait(f, &fifo->write_queue, wait);
+
+		if (ioread32(fifo->base_addr + XLLF_TDFV_OFFSET))
+			mask |= EPOLLOUT | EPOLLWRNORM;
+	}
+
+	return mask;
+}
+
 static irqreturn_t axis_fifo_irq(int irq, void *dw)
 {
 	struct axis_fifo *fifo = dw;
@@ -410,7 +433,8 @@ static const struct file_operations fops = {
 	.open = axis_fifo_open,
 	.release = axis_fifo_close,
 	.read = axis_fifo_read,
-	.write = axis_fifo_write
+	.write = axis_fifo_write,
+	.poll = axis_fifo_poll,
 };
 
 static int axis_fifo_debugfs_regs_show(struct seq_file *m, void *p)
-- 
2.51.0