Hi Florian,
On 05/09/13 16:15, Florian Echtler wrote:
> Hello everyone,
>
> as mentioned earlier, I'm currently writing a multitouch input driver
> for the Pixelsense (formerly Surface 2.0). It's now at a point where I'd
> consider it mostly done, but a) I have very limited experience with
> kernel drivers and b) there are some additional questions I have, so I'm
> attaching the current state of my source code and would like to ask for
> your comments.
Thanks for sharing this with us.
I will not do a proper review right now (just coming back from some days off,
so I am quickly emptying my mail box).
Some generic comments:
- please always inline the code in the message, it is *much* easier to review
and comment it
- please directly use a patch format: if the code is good, Dmitry can take it
directly through his tree
- add the following people for further submissions:
* Henrik - multitouch maintainer in the kernel, and I'm sure he will be happy
to see this stuff
* Dmitry - input maintainer, the driver will go through his tree, so it's
better to let him know as soon as possible of the different discussions.
- please stick to the kernel formatting guidelines (without orders: do not use
C99-style ("// ..."), do not mix tabs and spaces, stick to 80 columns, etc..).
The whole documentation is in Documentation/CodingStyle, and use the script
scripts/checkpatch.pl to validate most of these.
- I don't think a separate ".h" will be accepted as the declarations will not
be used outside of the driver. Just merge the header on top of you .c file.
>
> Open question: it looks like just calling
>
> input_mt_init_slots(poll_dev->input, MAX_CONTACTS, INPUT_MT_DIRECT);
>
> in the initialization routine isn't enough. hid-multitouch doesn't seem
> to use any other init commands, though, or did I overlook something?
>
> Are there any other caveats of the input-mt library which I should be
> aware of?
You need to also set up the different axes (ABS_MT_POSITION_X and others)
before calling input_mt_init_slots(). See setup_events_to_report() in bcm5974.c
for an example.
>
> Thanks for your input, and best regards, Florian
>
Few comments inlined:
> /*
> Surface2.0/SUR40/PixelSense input driver v0.0.1
>
> 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.
>
> Copyright (C) 2013 by Florian 'floe' Echtler <[email protected]>
>
> Derived from the USB Skeleton driver 1.1,
> Copyright (C) 2003 Greg Kroah-Hartman ([email protected])
>
> Derived from the Apple USB BCM5974 multitouch driver,
> Copyright (C) 2008 Henrik Rydberg ([email protected])
> */
>
>[snipped]
>
> /*
> * this function is called when a whole contact has been processed,
> * so that it can assign it to a slot and store the data there
> */
> static void report_blob(struct surface_blob *blob, struct input_dev *input)
> {
> int wide, major, minor;
>
> int slotnum = input_mt_get_slot_by_key(input, blob->blob_id);
> if (slotnum < 0 || slotnum >= MAX_CONTACTS)
> return;
>
> /* FIXME: is this needed for the Pixelsense? */
I doubt. This was required in hid-multitouch because we sometimes have "blobs"
without valuable information. So we drop them.
Here it looks like each blob contains information, so it should be fine without
this.
> /*if ((td->mtclass.quirks & MT_QUIRK_IGNORE_DUPLICATES) && mt) {
> struct input_mt *mt = input->mt;
> struct input_mt_slot *slot = &mt->slots[slotnum];
> if (input_mt_is_active(slot) &&
> input_mt_is_used(mt, slot))
> return;
> }*/
>
> input_mt_slot(input, slotnum);
> input_mt_report_slot_state(input, MT_TOOL_FINGER, 1);
looks like you never release the touch... :(
See below.
> wide = (blob->bb_size_x > blob->bb_size_y);
> major = max(blob->bb_size_x, blob->bb_size_y);
> minor = min(blob->bb_size_x, blob->bb_size_y);
>
> input_event(input, EV_ABS, ABS_MT_POSITION_X, blob->pos_x);
> input_event(input, EV_ABS, ABS_MT_POSITION_Y, blob->pos_y);
> input_event(input, EV_ABS, ABS_MT_TOOL_X, blob->ctr_x);
> input_event(input, EV_ABS, ABS_MT_TOOL_Y, blob->ctr_y);
> input_event(input, EV_ABS, ABS_MT_ORIENTATION, wide);
> input_event(input, EV_ABS, ABS_MT_TOUCH_MAJOR, major);
> input_event(input, EV_ABS, ABS_MT_TOUCH_MINOR, minor);
> }
>
>
[snipped]
>
> /* check candidate USB interface */
> static int surface_probe(struct usb_interface *interface,
> const struct usb_device_id *id)
> {
> struct usb_device *usbdev = interface_to_usbdev(interface);
> struct usb_surface *surface;
> struct usb_host_interface *iface_desc;
> struct usb_endpoint_descriptor *endpoint;
> struct input_polled_dev* poll_dev;
>
> /* check if we really have the right interface */
> iface_desc = &interface->altsetting[0];
> if (iface_desc->desc.bInterfaceClass != 0xFF)
> return -ENODEV;
>
> /* allocate memory for our device state and initialize it */
> surface = kzalloc(sizeof(struct usb_surface), GFP_KERNEL);
> poll_dev = input_allocate_polled_device();
> surface->input = poll_dev;
> if (!surface || !poll_dev)
> return -ENOMEM;
>
> poll_dev->private = surface;
> poll_dev->poll_interval = POLL_INTERVAL;
> poll_dev->open = surface_open;
> poll_dev->poll = surface_poll;
> poll_dev->close = surface_close;
>
> poll_dev->input->name = "Samsung SUR40";
> usb_to_input_id(usbdev,&(poll_dev->input->id));
> usb_make_path(usbdev, surface->phys, sizeof(surface->phys));
> strlcat(surface->phys, "/input0", sizeof(surface->phys));
> poll_dev->input->phys = surface->phys;
>
> input_mt_init_slots(poll_dev->input, MAX_CONTACTS, INPUT_MT_DIRECT);
If the device always reports actual touches and discards the release
information, you may need to use the flag INPUT_MT_DROP_UNUSED.
>
> surface->usbdev = usbdev;
> surface->interface = interface;
>
> /* use endpoint #4 (0x86) */
> endpoint = &iface_desc->endpoint[4].desc;
> if (endpoint->bEndpointAddress == TOUCH_ENDPOINT) {
> /* we found a bulk in endpoint */
> surface->bulk_in_size = le16_to_cpu(endpoint->wMaxPacketSize);
> surface->bulk_in_endpointAddr = endpoint->bEndpointAddress;
> surface->bulk_in_buffer = kmalloc(2*surface->bulk_in_size,
> GFP_KERNEL);
> if (!surface->bulk_in_buffer) {
> pr_err("Unable to allocate input buffer.");
> surface_delete(surface);
> return -ENOMEM;
> }
> }
>
> if (!(surface->bulk_in_endpointAddr)) {
> pr_err("Unable to find bulk-in endpoint.");
> surface_delete(surface);
> return -ENODEV;
> }
>
> /* we can register the device now, as it is ready */
> usb_set_intfdata(interface, surface);
>
> if (input_register_polled_device(poll_dev)) {
> pr_err("Unable to register polled input device.");
> surface_delete(surface);
> return -ENODEV;
> }
>
> dev_info(&interface->dev,"%s now attached\n",DRIVER_DESC);
>
> return 0;
> }
>
> [snipped]
>
> /* usb specific object needed to register this driver with the usb subsystem
> */
> static struct usb_driver surface_driver = {
> .name = DRIVER_SHORT,
> .probe = surface_probe,
> .disconnect = surface_disconnect,
> /*.suspend = surface_suspend,
> .resume = surface_resume,*/
if they are commented, they are not required, so just drop it :)
> .id_table = surface_table,
> /*.supports_autosuspend = 1,*/
ditto
> };
>
> module_usb_driver(surface_driver);
>
> MODULE_AUTHOR(DRIVER_AUTHOR);
> MODULE_DESCRIPTION(DRIVER_DESC);
> MODULE_LICENSE("GPL");
Cheers,
Benjamin
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