[PATCH v2] Documentation usb serial: fixed how to provide vendor and product id

[Marek Belisko <marek@goldelico.com>]

From: "H. Nikolaus Schaller" <hns@goldelico.com>

While trying to test a Cinterion GSM/GPS/3G module I had reconfigured
the USB interface by mistake and therefore needed to run a different
USB driver than CDC-ACM. It turned out that I need the "usbserial" driver.

This file is an official description how to use it: Documentation/usb/usb-serial.txt

But it is outdated. The parameters vendor= and product= are only available
if compiled as a kernel module and have been superseded by a /sys interface.

Here was the solution:

https://bbs.archlinux.org/viewtopic.php?id=175499

  insmod usbserial vendor=0x#### product=0x####

becomes (first #### is vendor, second is product)

  modprobe usbserial
  echo #### #### >/sys/bus/usb-serial/drivers/generic/new_id

This patch changes the documentation file to describe the modern variant.
Please note that the old one still works (if compiled as module).

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Marek Belisko <marek@goldelico.com>
---

changes from v1:
- add modern variant with /sys as preferred but also old one works so
  keep it in documentation (was removed in first version which was not correct)

 Documentation/usb/usb-serial.txt | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/usb/usb-serial.txt b/Documentation/usb/usb-serial.txt
index 947fa62..3f31c96 100644
--- a/Documentation/usb/usb-serial.txt
+++ b/Documentation/usb/usb-serial.txt
@@ -465,12 +465,15 @@ Generic Serial driver
   device, and does not support any kind of device flow control. All that
   is required of your device is that it has at least one bulk in endpoint,
   or one bulk out endpoint. 
-  
-  To enable the generic driver to recognize your device, build the driver
-  as a module and load it by the following invocation:
-	insmod usbserial vendor=0x#### product=0x####
+
+  To enable the generic driver to recognize your device, provide
+	echo #### #### >/sys/bus/usb-serial/drivers/generic/new_id
   where the #### is replaced with the hex representation of your device's
   vendor id and product id.
+  If the driver is compiled as a module, you can either
+	modprobe usbserial
+  or, you can also provide the parameters directly
+	insmod usbserial vendor=0x#### product=0x####
 
   This driver has been successfully used to connect to the NetChip USB
   development board, providing a way to develop USB firmware without
-- 
1.9.1