[PATCH 08/19] serdev: Provide modalias attribute for modalias devices

[Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>]

Create modalias sysfs attribute for modalias devices.
This is required by modprobe/udev to autoload the serdev driver.

Eg:
root@qt5022:~# cat /sys/bus/serial/devices/serial1-0/modalias
serdev:ttydev

Cc: Rob Herring <robh@kernel.org>
Cc: Johan Hovold <johan@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
---
 drivers/tty/serdev/core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index e695fa649a6d..a9c935f68076 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -23,12 +23,17 @@ static ssize_t modalias_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
 	int len;
+	struct serdev_device *serdev = to_serdev_device(dev);
 
 	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
 	if (len != -ENODEV)
 		return len;
 
-	return of_device_modalias(dev, buf, PAGE_SIZE);
+	len = of_device_modalias(dev, buf, PAGE_SIZE);
+	if (len != -ENODEV)
+		return len;
+
+	return sprintf(buf, "%s%s\n", SERDEV_MODULE_PREFIX, serdev->modalias);
 }
 static DEVICE_ATTR_RO(modalias);
 
-- 
2.17.0