Synaptics cPad Linux driver for kernel 2.6

Latest: cpad26-0.9-3.tar.bz2
The cPad is an USB touchpad with background display (240x160 mono). If you don't want to use the display, you do not need this driver. The cPad emulates an USB mouse by default, so you can use the usbhid kernel module. But you will be able to use Synaptics TouchPad driver for XFree86 in combination with this kernel module, which will greatly improve mouse movement. The Display can be accessed via a frame buffer device and via a character device. A driver for kernel 2.4 is available at Rob Miller's page.

cPad and Debian

Ron Lee works on Debian packages for the cPad. The kernel modules are already available, user space programs maybe follow soon :-)

Problems with usbhid.ko

The conflict with usbhid.ko has been solved by Ron and me in the latest release. But if you have more than one cPad, you will still need to patch the kernel ;)

Installation

The sources of your kernel must be installed and configured.

Configuring the kernel

At least, you need USB support in the kernel:

	CONFIG_USB: y/m
		Device Drivers --->
		    USB support --->
			Support for Host-side USB

USB will only work, if you have the right driver(s) for your USB host controller. My Toshiba Laptop needs both the EHCI and the OHCI driver. If unsure, just select all:

	CONFIG_USB_EHCI_HCD and/or CONFIG_USB_OHCI_HCD and/or CONFIG_USB_UHCI_HCD: y/m
		Device Drivers --->
		    USB support --->
			EHCI HCD (USB 2.0) support
			OHCI HCD support
			UHCI HCD (most Intel and VIA) support

Synaptics TouchPad driver for XFree86 needs an evdev interface:

	CONFIG_INPUT_EVDEV: y/m
		Device Drivers --->
		    Input device support --->
			Event interface

If you want to use the procfs interface, you also need this:

	CONFIG_PROC_FS: y
		File systems --->
		    Pseudo filesystems --->
			/proc file system support

If you want to use the frame buffer you need:

	CONFIG_FB and CONFIG_FB_VESA: y
		Device Drivers --->
		    Graphics support --->
			Support for frame buffer devices
			VESA VGA graphics support

Mapping a tty on the frame buffer needs this kernel option:

	CONFIG_FRAMEBUFFER_CONSOLE: y/m
		Device Drivers --->
		    Graphics support --->
			Console display driver support --->
			    Framebuffer Console support

Installing the cpad kernel module

To compile the module, run:

	make

To install the module, run:

	make install
	depmod -a

Synaptics TouchPad driver for XFree86

To enable features like tap-to-click, vertical/horizontal scrolling, multifinger taps, etc you need Synaptics TouchPad driver for XFree86 version >= 0.13.3 in addition to this kernel module.

Programs for the cPad character device

If you want to flash the backlight and display nice pictures on the cPad, then the program usr_cpad is the best choice. It is included in the tarball of the kernel 2.4 driver, available at Rob Miller's page. There is also a gallery with examples, scripts ...
I have written the tool cpadconsole, which can help developing programs for the character device.

Using the procfs interface

The files /proc/driver/cpad/* show some information about the cPad.

Flashing the backlight

	echo "flash:<time in 10ms>" > /proc/driver/cpad/0

Enabling the frame buffer (disabled by default)

	echo "framerate:<rate>" > /proc/driver/cpad/0

Disabling the frame buffer

	echo "framerate:0" > /proc/driver/cpad/0

Frame buffer dithering mode (default is 3; only in 24 bpp mode)

	echo "dithering:<number from 0 to 3>" > /proc/driver/cpad/0

Frame buffer brightness (default is 200; only in 24 bpp mode)

	echo "brightness:<number from 0 to 10000>" > /proc/driver/cpad/0

Invert black and white

	echo "invert:1" > /proc/driver/cpad/0

Send only changed image lines

	echo "onlychanged:1" > /proc/driver/cpad/0

Update only visible part of cPad memory (only in 1 bpp mode)

	echo "onlyvisible:1" > /proc/driver/cpad/0

Draw only one frame

	echo "oneframe" > /proc/driver/cpad/0

Using the frame buffer device

The frame buffer is disabled by default. You can enable it with

	echo "framerate:30" > /proc/driver/cpad/0

The following examples assume that your primary display is /dev/fb0, so your touchpad is the second frame buffer device /dev/fb1. If you don't use vesafb or any other frame buffer, then your cPad will be /dev/fb0.

Emulate 24 bpp

Most applications do not like frame buffers with 1 bpp. The cPad frame buffer can emulate 24 bpp. You can switch to 24 bpp with fbset:

	fbset -fb /dev/fb1 -depth 24

All examples below need 24 bpp.

Playing movies

	mplayer -vo fbdev -fb /dev/fb1 -vf scale=240:160 <file>

Running XFree86

You just need the following lines in the driver section of your XF86Config file:

	Driver		"fbdev"
	Option		"fbdev"	"/dev/fb1"

Map a tty to the frame buffer

Some programs need a tty on the frame buffer to run correctly. You need the program con2fb to map a tty to a frame buffer device. You can also use fbgetty, wich gives you a login prompt automatically. Example: Do 'fbgetty /dev/tty9 /dev/fb1', then press <ALT>+<F9> and you should be able to login. It looks better if you invert the screen with:

	echo "invert:1" > /proc/driver/cpad/0

Other Software for frame buffer devices

http://linux-fbdev.sourceforge.net

Module parameters

Disable input devices

	modprobe cpad disable_input=1

Disable character device

	modprobe cpad disable_cdev=1

Disable procfs interface

	modprobe cpad disable_procfs=1

Disable frame buffer

	modprobe cpad disable_fb=1

Set maximum bpp to 1 (saves 108k memory)

	modprobe cpad max_bpp=1

cPad and udev

Udev will replace devfs some day. Udev with its standard configuration creates the cPad character device as /dev/cpad0, but it should be /dev/usb/cpad0. If you already use udev, you may want to try these config files:
cpad.rules
cpadsymlinks.sh

Copy cpad.rules to /etc/udev/rules.d/ and cpadsymliks.sh to /etc/udev/scripts/. cpadsymlinks.sh must be executable. This config files will also create a directory /dev/cpad/0/ which contains symlinks to all devices that belong to the cpad.

Bugs

With kernel >= 2.6.7 rmmod hangs while the evdev device of the cPad (/dev/input/event?) is in use. usbhid.ko seems to have the same problem. If you are using Synaptics TouchPad driver for XFree86 and do rmmod from xterm, it will hang. Switching to console and then back to X helps. This was a bug in the input core, now fixed in kernel 2.6.10.

Changes

version 0.9-3:

Some changes in the way this driver gets the cPad from usbhid
version 0.9-2:

procfs broke in 0.9. Now it works again.
version 0.9:

Grab the cPad back from any driver that has already claimed it. Leap ahead a couple of versions to sync with the 2.4 driver, so people upgrading see a more or less monotonic increase in version numbers (and because the Debian build of 0.5 already released with DRIVER_VERSION of v0.8). Let's aim for v1.0 to be accepted into the mainstream kernel tree.
version 0.6:

invert screen now possible in 1 bpp mode too
version 0.5:

Replaced deprecated MODULE_PARM and remap_page_range.

Merged with the 2.4 package as the cpad-0.8 release.
version 0.4:

replaced del_timer_sync with del_timer in interrupt context (bad bug)
version 0.3:

replaced interruptible_sleep_on_timeout with wait_event_interruptible_timeout

removed some inline's

show more information in procfs

add support for 1 bpp to frame buffer

add ioctl's to frame buffer

add oneframe, onlychanged and onlyvisible options to frame buffer
version 0.2:

fixed a color to mono conversion bug

added a pseudo_palette (needed by virtual terminals)
version 0.1: first release

E-Mail: jan.steinhoff@uni-jena.de