serial: sa1100: add note about modem control signals

As suggested by Uwe, add a note indicating that the modem control
signals do not support interrupts, which precludes the driver from
using mctrl_gpio_init().

Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

diff --git a/drivers/tty/serial/sa1100.c b/drivers/tty/serial/sa1100.c
index 97bdfec..8e61812 100644 (file)
--- a/drivers/tty/serial/sa1100.c
+++ b/drivers/tty/serial/sa1100.c
@@ -860,6 +860,10 @@ static int sa1100_serial_resume(struct platform_device *dev)
 static int sa1100_serial_add_one_port(struct sa1100_port *sport, struct platform_device *dev)
 {
        sport->port.dev = &dev->dev;
+
+       // mctrl_gpio_init() requires that the GPIO driver supports interrupts,
+       // but we need to support GPIO drivers for hardware that has no such
+       // interrupts.  Use mctrl_gpio_init_noauto() instead.
        sport->gpios = mctrl_gpio_init_noauto(sport->port.dev, 0);
        if (IS_ERR(sport->gpios)) {
                int err = PTR_ERR(sport->gpios);