linux-kernel - [PATCH 2/7] tty: serial: Add poll_get

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Date:   Mon, 22 Jun 2020 19:56:19 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     kgdb-bugreport@...ts.sourceforge.net, linux-serial@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, daniel.thompson@...aro.org,
        jason.wessel@...driver.com, dianders@...omium.org, jslaby@...e.com,
        linux@...linux.org.uk, linux-kernel@...r.kernel.org,
        Sumit Garg <sumit.garg@...aro.org>
Subject: [PATCH 2/7] tty: serial: Add poll_get_irq() to the polling interface

From: Daniel Thompson <daniel.thompson@...aro.org>

Add new API: poll_get_irq() to the polling interface in order for user
of polling interface to retrieve allocated IRQ corresponding to
underlying serial device.

Although, serial interface still works in polling mode but interrupt
associated with serial device can be leveraged for special purposes like
debugger(kgdb) entry.

Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
---
 drivers/tty/serial/serial_core.c | 18 ++++++++++++++++++
 include/linux/serial_core.h      |  1 +
 include/linux/tty_driver.h       |  1 +
 3 files changed, 20 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 66a5e2f..1bb033c 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2470,6 +2470,23 @@ static void uart_poll_put_char(struct tty_driver *driver, int line, char ch)
 	port->ops->poll_put_char(port, ch);
 	uart_port_deref(port);
 }
+
+static int uart_poll_get_irq(struct tty_driver *driver, int line)
+{
+	struct uart_driver *drv = driver->driver_state;
+	struct uart_state *state = drv->state + line;
+	struct uart_port *port;
+	int ret = -ENODEV;
+
+	port = uart_port_ref(state);
+	if (port && port->ops->poll_get_irq) {
+		ret = port->ops->poll_get_irq(port);
+		uart_port_deref(port);
+	}
+
+	return ret;
+}
+
 #endif
 
 static const struct tty_operations uart_ops = {
@@ -2505,6 +2522,7 @@ static const struct tty_operations uart_ops = {
 	.poll_init	= uart_poll_init,
 	.poll_get_char	= uart_poll_get_char,
 	.poll_put_char	= uart_poll_put_char,
+	.poll_get_irq	= uart_poll_get_irq,
 #endif
 };
 
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 92f5eba..8b132e6 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -78,6 +78,7 @@ struct uart_ops {
 	int		(*poll_init)(struct uart_port *);
 	void		(*poll_put_char)(struct uart_port *, unsigned char);
 	int		(*poll_get_char)(struct uart_port *);
+	int		(*poll_get_irq)(struct uart_port *);
 #endif
 };
 
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 3584462..d6da5c5 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -295,6 +295,7 @@ struct tty_operations {
 	int (*poll_init)(struct tty_driver *driver, int line, char *options);
 	int (*poll_get_char)(struct tty_driver *driver, int line);
 	void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
+	int (*poll_get_irq)(struct tty_driver *driver, int line);
 #endif
 	int (*proc_show)(struct seq_file *, void *);
 } __randomize_layout;
-- 
2.7.4