USB: add read support to usb-serial/../new_id

Keep the usb-serial support for dynamic IDs in sync with the usb
support.  This enables readout of dynamic device IDs for
usb-serial drivers.  Common code is exported from the usb core
system and reused by the usb-serial bus driver.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index ed8adb052ca7..f398d1e34474 100644
--- a/drivers/usb/serial/bus.c
+++ b/drivers/usb/serial/bus.c
@@ -124,8 +124,15 @@ static ssize_t store_new_id(struct device_driver *driver,
         return retval;
 }
 
+static ssize_t show_dynids(struct device_driver *driver, char *buf)
+{
+        struct usb_serial_driver *usb_drv = to_usb_serial_driver(driver);
+
+        return usb_show_dynids(&usb_drv->dynids, buf);
+}
+
 static struct driver_attribute drv_attrs[] = {
-        __ATTR(new_id, S_IWUSR, NULL, store_new_id),
+        __ATTR(new_id, S_IRUGO | S_IWUSR, show_dynids, store_new_id),
         __ATTR_NULL,
 };