Synaptics cPad Linux driver for kernel 2.6

Latest: version 1.1
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 character device. A driver for kernel 2.4 is available at Rob Miller's page.
The older versions of this kernel module included a frame buffer device, which is now split into a second kernel module and a user space program. The procfs interface is gone now, because it was mainly used to control the framebuffer. If you do not like this, you can get the older version here.

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 since version 0.9. At module initialisation, the cPad driver takes over the cPad from usbhid. If you hotplug a cPad, then you must maybe initiate another takeover manually with:

	echo "1" > /sys/module/cpad/parameters/steal

Sometimes at startup the cPad reconnects. If this happens after module initialisation, you will have to initiate a takeover manually too.
If you have more than one cPad, you will need to patch the kernel (this kernel patch makes sure that usbhid will not handle the cPad any more).

Installation

The sources of your kernel must be installed and configured. In most cases the standard configuration of your kernel should already work (maybe you want to skip the next section first).

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

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. The example configuration for /etc/X11/XF86Config that comes with this driver should work fine. Don't forget to check if you have evdev compiled into the kernel or as a module, otherwise it will not work.

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 ... Here is a slightly modified version of usr_cpad, which can send the images a bit faster.
Ron Lee has updated his cpad-mux debian packages. It is still work in progress, but a calculator already works!
With cpadfb you can put a frame buffer on the cPad.
The tool cpadconsole can help developing programs for the character device.

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 use 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.

Module parameters

Calibrate abs finger position

If you want to use the /dev/input/ts? (emulates Compaq Touchscreen protocol) device of the cPad, you maybe want to adjust the following values:

	modprobe xmin=<value> xmax=<value> ymin=<value> ymax=<value>

The default values are:

	xmin=1472
	xmax=5472
	ymin=1408
	ymax=4448

Let usbhid handle the cpad

	modprobe cpad steal=0

Bug

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 1.1:

fixed compilation errors for kernel versions < 2.6.10
version 1.0:

the driver has now only an input and a character device, and is based on usb_skeleton.c version 2.0
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