On Wed, Nov 24, 2010 at 11:07:00AM -0500, Jeremy Moles wrote: > Hello everyone! I have a piece of hardware here using a vanilla 2.6.34 > kernel (though I can easily change kernels if needed) that has attached > to it internally a USB touchscreen device. The relevant DMESG info is > below, and this is printed out whenever the module 'usbhid' is loaded. > > -------------------------------------------------------------------- > > usbcore: registered new interface driver hiddev > input: Fujitsu Component USB Touch Panel > as /devices/pci0000:00/0000:00:1a.0/usb3/3-2/3-2:1.0/input/input9 > generic-usb 0003:0430:0501.0002: input: USB HID v1.00 Mouse [Fujitsu > Component USB Touch Panel] on usb-0000:00:1a.0-2/input0 > usbcore: registered new interface driver usbhid > usbhid: USB HID core driver > > -------------------------------------------------------------------- > > For a long time now, we have been successfully configuring these > machines using the device node created when this driver is loaded, often > something like /dev/input/event5 (with a UDEV rule to make the name more > sensible). In X, we've been using the "evtouch" driver with this device > node, to great effect. > > However, I am doing a bit of research and experimentation, and what I > would like to do is write some custom driver code to interface with this > device, instead of letting usbhid manage it. My question is, where is > the best place to start? I guess you need to enumerate what deficiencies usbhid has and what issues you want to solve. That would clear a lot. I think that completely abandoning HID driver for device that is mostly HID compliant is not the best idea and you probably want to wire a HID sub-driver that works in tandem with usbhid. > > - Since usbhid already recognizes and binds to this device, what code > can I begin studying to see exactly how it's detecting this and > formatting input? I guess drivers/hid/hid-input.c is the most interesting one. > > - Once usbhid attaches to this device, is the device in some kind of > lock? Is it possible to simply inject additional features or formatting > functions, possibly via quirks? (I don't quite understand how to do > anything with quirks other than blacklist a device). Only one driver can manage a device so once HID claimed it your standalone driver will not be able to control it. However there is notion of HID bus drivers (you looked at hid-ntrig - it's one of them) that allow you to override and/or augment processing done by the default HID driver. > > - If I want to write a full driver for the device, what source file > would be best to start from? I've tried hacking usbtouchscreen.c and > hid-ntrig.c for the last few days to try and get them to bind to the > device, but neither attempt has seen any success. My hid-ntrig change > refuses to successfully call hid_parse(), and my usbtouchscreen change > continually returns some error code in the IRQ callback. Did you add the VID/PID of your device to the blacklist in drivers/hid/hid-core.c? -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
