On Sat, 2010-11-27 at 19:07 -0800, Dmitry Torokhov wrote: > On Sat, Nov 27, 2010 at 09:23:30PM -0500, Jeremy Moles wrote: > > On Sat, 2010-11-27 at 15:51 -0800, Dmitry Torokhov wrote: > > > 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. > > > > I think you're absolutely right about a sub-driver of sorts. > > > > Essentially it comes down to this: the touchscreen is being used in > > hardware running Android, and the Android userspace code expects an > > input event device to support the BTN_TOUCH ioctl. However, seeing as > > usbhid binds to this device in a very generic way, it doesn't add the > > BTN_TOUCH bits, and rightly so. In regular X, the evtouch driver does > > not require this particular feature, so the device works fine. > > > > HOWEVER, if I remove this check from the Android userspace library tslib > > (the ioctl query for BTN_TOUCH), it does at least act as a pointer > > inside Android's display manager, although there is no notion of > > pressure--it's either 255 or 0 in tslib terms. I'm not entirely sure the > > device even supports pressure, but that is why I'm researching this > > project. :) > > > > > > > > > > - 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. > > > > This is definitely what I'm interested in. I stripped its code down to > > basically just the probe function. It recognizes my USB PCIID but fails > > to call hid_parse() with the error -19. I've not been able to lock down > > where the ll_driver->hid_parse() function is to see exactly what this > > error might be. > > > > > > > > > > - 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? > > > > Yes, and this does prevent usbhid from picking it up. I can also add a > > quirk to modprobe.conf dynamically adding the HID_QUIRK_IGNORE quirk to > > achieve the same effect. In fact, this is necessary for my "hacked" > > hid-testdriver.c module to even TRY and call the probe function. > > Well, if you add HID_QUIRK_IGNORE then in usbhid_parse: > > > quirks = usbhid_lookup_quirk(le16_to_cpu(dev->descriptor.idVendor), > le16_to_cpu(dev->descriptor.idProduct)); > > if (quirks & HID_QUIRK_IGNORE) > return -ENODEV; > > and -ENODEV is -19 so it is no surprise you are getting -19 from > hid_parse(). > > You need to make sure you are adding entry to > > drivers/hid/hid-core.c:static const struct hid_device_id hid_blacklist[] > > and not to > > drivers/hid/usbhid/hid-quirks.c:static const struct hid_blacklist > > Hmm, I wonder if we should rename the first one to something different, > like hid_has_custom_driver. Jiri? WHOA! Now we're cooking! My probe succeeds and now my event/input_mapping/input_mapped functions all get called! When driver developers are writing HID glue drivers like this, how is it you generally determine the contents of your drv_data structure? Via hardware specs or is there some way to poke at the device via USB and have it tell you? Perhaps this question is a bit TOO out of line, as I'm sure that information is available in the standard USB HID information... -- 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
