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diff --git a/Documentation/usb/gadget_serial.rst b/Documentation/usb/gadget_serial.rst new file mode 100644 index 000000000..dce8bc1fb --- /dev/null +++ b/Documentation/usb/gadget_serial.rst @@ -0,0 +1,289 @@ +=============================== +Linux Gadget Serial Driver v2.0 +=============================== + +11/20/2004 + +(updated 8-May-2008 for v2.3) + + +License and Disclaimer +---------------------- +This program is free software; you can redistribute it and/or +modify it under the terms of the GNU General Public License as +published by the Free Software Foundation; either version 2 of +the License, or (at your option) any later version. + +This program is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public +License along with this program; if not, write to the Free +Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, +MA 02111-1307 USA. + +This document and the gadget serial driver itself are +Copyright (C) 2004 by Al Borchers (alborchers@steinerpoint.com). + +If you have questions, problems, or suggestions for this driver +please contact Al Borchers at alborchers@steinerpoint.com. + + +Prerequisites +------------- +Versions of the gadget serial driver are available for the +2.4 Linux kernels, but this document assumes you are using +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 +Windows and know how to configure and build Linux kernels, run +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 +-------- +The gadget serial driver is a Linux USB gadget driver, a USB device +side driver. It runs on a Linux system that has USB device side +hardware; for example, a PDA, an embedded Linux system, or a PC +with a USB development card. + +The gadget serial driver talks over USB to either a CDC ACM driver +or a generic USB serial driver running on a host PC:: + + Host + -------------------------------------- + | Host-Side CDC ACM USB Host | + | Operating | or | Controller | USB + | System | Generic USB | Driver |-------- + | (Linux or | Serial | and | | + | Windows) Driver USB Stack | | + -------------------------------------- | + | + | + | + Gadget | + -------------------------------------- | + | Gadget USB Periph. | | + | Device-Side | Gadget | Controller | | + | Linux | Serial | Driver |-------- + | Operating | Driver | and | + | System USB Stack | + -------------------------------------- + +On the device-side Linux system, the gadget serial driver looks +like a serial device. + +On the host-side system, the gadget serial device looks like a +CDC ACM compliant class device or a simple vendor specific device +with bulk in and bulk out endpoints, and it is treated similarly +to other serial devices. + +The host side driver can potentially be any ACM compliant driver +or any driver that can talk to a device with a simple bulk in/out +interface. Gadget serial has been tested with the Linux ACM driver, +the Windows usbser.sys ACM driver, and the Linux USB generic serial +driver. + +With the gadget serial driver and the host side ACM or generic +serial driver running, you should be able to communicate between +the host and the gadget side systems as if they were connected by a +serial cable. + +The gadget serial driver only provides simple unreliable data +communication. It does not yet handle flow control or many other +features of normal serial devices. + + +Installing the Gadget Serial Driver +----------------------------------- +To use the gadget serial driver you must configure the Linux gadget +side kernel for "Support for USB Gadgets", for a "USB Peripheral +Controller" (for example, net2280), and for the "Serial Gadget" +driver. All this are listed under "USB Gadget Support" when +configuring the kernel. Then rebuild and install the kernel or +modules. + +Then you must load the gadget serial driver. To load it as an +ACM device (recommended for interoperability), do this:: + + modprobe g_serial + +To load it as a vendor specific bulk in/out device, do this:: + + modprobe g_serial use_acm=0 + +This will also automatically load the underlying gadget peripheral +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 +Linux generic serial driver on the host side. Follow the appropriate +instructions below to install the host side driver. + + +Installing the Windows Host ACM Driver +-------------------------------------- +To use the Windows ACM driver you must have the "linux-cdc-acm.inf" +file (provided along this document) which supports all recent versions +of Windows. + +When the gadget serial driver is loaded and the USB device connected +to the Windows host with a USB cable, Windows should recognize the +gadget serial device and ask for a driver. Tell Windows to find the +driver in the folder that contains the "linux-cdc-acm.inf" file. + +For example, on Windows XP, when the gadget serial device is first +plugged in, the "Found New Hardware Wizard" starts up. Select +"Install from a list or specific location (Advanced)", then on the +next screen select "Include this location in the search" and enter the +path or browse to the folder containing the "linux-cdc-acm.inf" file. +Windows will complain that the Gadget Serial driver has not passed +Windows Logo testing, but select "Continue anyway" and finish the +driver installation. + +On Windows XP, in the "Device Manager" (under "Control Panel", +"System", "Hardware") expand the "Ports (COM & LPT)" entry and you +should see "Gadget Serial" listed as the driver for one of the COM +ports. + +To uninstall the Windows XP driver for "Gadget Serial", right click +on the "Gadget Serial" entry in the "Device Manager" and select +"Uninstall". + + +Installing the Linux Host ACM Driver +------------------------------------ +To use the Linux ACM driver you must configure the Linux host side +kernel for "Support for Host-side USB" and for "USB Modem (CDC ACM) +support". + +Once the gadget serial driver is loaded and the USB device connected +to the Linux host with a USB cable, the host system should recognize +the gadget serial device. For example, the command:: + + cat /sys/kernel/debug/usb/devices + +should show something like this::: + + T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 5 Spd=480 MxCh= 0 + D: Ver= 2.00 Cls=02(comm.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 + P: Vendor=0525 ProdID=a4a7 Rev= 2.01 + S: Manufacturer=Linux 2.6.8.1 with net2280 + S: Product=Gadget Serial + S: SerialNumber=0 + C:* #Ifs= 2 Cfg#= 2 Atr=c0 MxPwr= 2mA + I: If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=01 Driver=acm + E: Ad=83(I) Atr=03(Int.) MxPS= 8 Ivl=32ms + I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=acm + E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms + E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms + +If the host side Linux system is configured properly, the ACM driver +should be loaded automatically. The command "lsmod" should show the +"acm" module is loaded. + + +Installing the Linux Host Generic USB Serial Driver +--------------------------------------------------- +To use the Linux generic USB serial driver you must configure the +Linux host side kernel for "Support for Host-side USB", for "USB +Serial Converter support", and for the "USB Generic Serial Driver". + +Once the gadget serial driver is loaded and the USB device connected +to the Linux host with a USB cable, the host system should recognize +the gadget serial device. For example, the command:: + + cat /sys/kernel/debug/usb/devices + +should show something like this::: + + T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 6 Spd=480 MxCh= 0 + D: Ver= 2.00 Cls=ff(vend.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 + P: Vendor=0525 ProdID=a4a6 Rev= 2.01 + S: Manufacturer=Linux 2.6.8.1 with net2280 + S: Product=Gadget Serial + S: SerialNumber=0 + C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 2mA + I: If#= 0 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=serial + E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms + E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms + +You must load the usbserial driver and explicitly set its parameters +to configure it to recognize the gadget serial device, like this:: + + echo 0x0525 0xA4A6 >/sys/bus/usb-serial/drivers/generic/new_id + +The legacy way is to use module parameters:: + + modprobe usbserial vendor=0x0525 product=0xA4A6 + +If everything is working, usbserial will print a message in the +system log saying something like "Gadget Serial converter now +attached to ttyUSB0". + + +Testing with Minicom or HyperTerminal +------------------------------------- +Once the gadget serial driver and the host driver are both installed, +and a USB cable connects the gadget device to the host, you should +be able to communicate over USB between the gadget and host systems. +You can use minicom or HyperTerminal to try this out. + +On the gadget side run "minicom -s" to configure a new minicom +session. Under "Serial port setup" set "/dev/ttygserial" as the +"Serial Device". Set baud rate, data bits, parity, and stop bits, +to 9600, 8, none, and 1--these settings mostly do not matter. +Under "Modem and dialing" erase all the modem and dialing strings. + +On a Linux host running the ACM driver, configure minicom similarly +but use "/dev/ttyACM0" as the "Serial Device". (If you have other +ACM devices connected, change the device name appropriately.) + +On a Linux host running the USB generic serial driver, configure +minicom similarly, but use "/dev/ttyUSB0" as the "Serial Device". +(If you have other USB serial devices connected, change the device +name appropriately.) + +On a Windows host configure a new HyperTerminal session to use the +COM port assigned to Gadget Serial. The "Port Settings" will be +set automatically when HyperTerminal connects to the gadget serial +device, so you can leave them set to the default values--these +settings mostly do not matter. + +With minicom configured and running on the gadget side and with +minicom or HyperTerminal configured and running on the host side, +you should be able to send data back and forth between the gadget +side and host side systems. Anything you type on the terminal +window on the gadget side should appear in the terminal window on +the host side and vice versa. |