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authorDavid Brownell <dbrownell@users.sourceforge.net>2008-06-19 17:52:07 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2008-07-21 15:15:59 -0700
commita7707adf9ee8de3c5b67e3793b98888f551ad00d (patch)
tree431137e4c39202f6395f64893966e3bdfa1349d2 /Documentation
parentc1dca562be8ada614ef193aa246c6f8705bcd6b9 (diff)
downloadlwn-a7707adf9ee8de3c5b67e3793b98888f551ad00d.tar.gz
lwn-a7707adf9ee8de3c5b67e3793b98888f551ad00d.zip
usb gadget: use new serial core
Teach "gadget serial" to use the new abstracted (and bugfixed) TTY glue, and remove all the orignal tangled-up code. Update the documentation accordingly. This is a net object code shrink and cleanup; it should make it a lot easier to see how the TTY glue should accomodate updates to the TTY layer, be bugfixed, etc. Notable behavior changes include: it can now support getty even when there's no USB connection; it fits properly into the mdev/udev world; and RX handling is better (throttling works, and low latency). Configurations with scripts setting up the /dev/ttygserial device node (with "experimental" major number) may want to change that to be a symlink pointing to the /dev/ttyGS0 file, as a migration aid; else, just switch entirely over to mdev/udev. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/usb/gadget_serial.txt35
1 files changed, 26 insertions, 9 deletions
diff --git a/Documentation/usb/gadget_serial.txt b/Documentation/usb/gadget_serial.txt
index 815f5c2301ff..9b22bd14c348 100644
--- a/Documentation/usb/gadget_serial.txt
+++ b/Documentation/usb/gadget_serial.txt
@@ -1,6 +1,7 @@
Linux Gadget Serial Driver v2.0
11/20/2004
+ (updated 8-May-2008 for v2.3)
License and Disclaimer
@@ -31,7 +32,7 @@ Prerequisites
-------------
Versions of the gadget serial driver are available for the
2.4 Linux kernels, but this document assumes you are using
-version 2.0 or later of the gadget serial driver in a 2.6
+version 2.3 or later of the gadget serial driver in a 2.6
Linux kernel.
This document assumes that you are familiar with Linux and
@@ -40,6 +41,12 @@ standard utilities, use minicom and HyperTerminal, and work with
USB and serial devices. It also assumes you configure the Linux
gadget and usb drivers as modules.
+With version 2.3 of the driver, major and minor device nodes are
+no longer statically defined. Your Linux based system should mount
+sysfs in /sys, and use "mdev" (in Busybox) or "udev" to make the
+/dev nodes matching the sysfs /sys/class/tty files.
+
+
Overview
--------
@@ -104,15 +111,8 @@ driver. All this are listed under "USB Gadget Support" when
configuring the kernel. Then rebuild and install the kernel or
modules.
-The gadget serial driver uses major number 127, for now. So you
-will need to create a device node for it, like this:
-
- mknod /dev/ttygserial c 127 0
-
-You only need to do this once.
-
Then you must load the gadget serial driver. To load it as an
-ACM device, do this:
+ACM device (recommended for interoperability), do this:
modprobe g_serial use_acm=1
@@ -125,6 +125,23 @@ controller driver. This must be done each time you reboot the gadget
side Linux system. You can add this to the start up scripts, if
desired.
+Your system should use mdev (from busybox) or udev to make the
+device nodes. After this gadget driver has been set up you should
+then see a /dev/ttyGS0 node:
+
+ # ls -l /dev/ttyGS0 | cat
+ crw-rw---- 1 root root 253, 0 May 8 14:10 /dev/ttyGS0
+ #
+
+Note that the major number (253, above) is system-specific. If
+you need to create /dev nodes by hand, the right numbers to use
+will be in the /sys/class/tty/ttyGS0/dev file.
+
+When you link this gadget driver early, perhaps even statically,
+you may want to set up an /etc/inittab entry to run "getty" on it.
+The /dev/ttyGS0 line should work like most any other serial port.
+
+
If gadget serial is loaded as an ACM device you will want to use
either the Windows or Linux ACM driver on the host side. If gadget
serial is loaded as a bulk in/out device, you will want to use the