[PATCH v2 1/6] serial: core: Add uart_console_port()

[Alexey Charkov <alchark@gmail.com>]

Console ->setup() and ->write() callbacks need the port behind
co->index. Most drivers keep a static port array just for that lookup,
and the few that skip it read the uart_driver state table, which the
header reserves for the core.

Provide the lookup next to uart_console_device(), which already relies
on co->data pointing at the uart_driver. The core links a port into the
state table before registering its console and unregisters the console
before unlinking the port, so the result stays valid in both callbacks.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
---
 drivers/tty/serial/serial_core.c | 21 +++++++++++++++++++++
 include/linux/serial_core.h      |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index b06d2649be34..683ffb4fda92 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2890,6 +2890,27 @@ struct tty_driver *uart_console_device(struct console *co, int *index)
 }
 EXPORT_SYMBOL_GPL(uart_console_device);
 
+/**
+ * uart_console_port - look up the port behind a console
+ * @co: console whose @data points at its &struct uart_driver
+ *
+ * Serial core registers a port's console only after linking the port into
+ * the driver's state table, and unregisters it before unlinking the port, so
+ * the result stays valid for the console's ->setup() and ->write() callbacks.
+ *
+ * Return: the port registered on line @co->index, or %NULL if there is none.
+ */
+struct uart_port *uart_console_port(struct console *co)
+{
+	struct uart_driver *drv = co->data;
+
+	if (co->index < 0 || co->index >= drv->nr)
+		return NULL;
+
+	return drv->state[co->index].uart_port;
+}
+EXPORT_SYMBOL_GPL(uart_console_port);
+
 static ssize_t uartclk_show(struct device *dev,
 	struct device_attribute *attr, char *buf)
 {
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 4eeb8253752a..9ac1ce1c10b5 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -1127,6 +1127,7 @@ void uart_parse_options(const char *options, int *baud, int *parity, int *bits,
 int uart_set_options(struct uart_port *port, struct console *co, int baud,
 		     int parity, int bits, int flow);
 struct tty_driver *uart_console_device(struct console *co, int *index);
+struct uart_port *uart_console_port(struct console *co);
 void uart_console_write(struct uart_port *port, const char *s,
 			unsigned int count,
 			void (*putchar)(struct uart_port *, unsigned char));

-- 
2.56.0