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A driver for XP-PEN G430S_B (black) tablet #397

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A driver for XP-PEN G430S_B (black) tablet #397

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230 changes: 230 additions & 0 deletions hid-g430sb.c
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// SPDX-License-Identifier: GPL-2.0+
/*
* HID driver for XP-PEN G430S_B (black) tablet, which is not fully compliant with HID standard
* Based on hid-viewsonic.c by Copyright (c) 2017 Nikolai Kondrashov
* Version: 1.1
*
* Copyright (c) 2020 Sturwandan
*/

/*
* 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.
*/

#include <linux/device.h>
#include <linux/hid.h>
#include <linux/module.h>
#include <linux/usb.h>

#include "usbhid/usbhid.h"
#include "hid-ids.h"

/* Size of the original descriptor of G430S_B pen */
#define G430SB_RDESC_ORIG_SIZE 36
/* We only need to work with interface 2 and ignore 0 and 1 */
#define G430SB_PEN_INTERFACE 2

/* Fixed report descriptor for XP-PEN G430S_B 's pen
* This format is sent after initialization.
* If the tablet is not initialized, the format is similar,
* but there are only two 0x00 bytes at the end and
* coordinates go from 0 to 32767 instead of native values
* which are approximately Physical values in units of 10^-3 cm.
* The report has following format, LE and ls bit first
*Bits Type
*8 ID=0x02
*1 TipSwitch
*1 BarrelSwitch
*1 BarrelSwitch2
*1 Const = 0 (invert)
*1 Const = 0
*1 InRange
*1 NotInRange (Unused)
*1 Const = 1
*16 X
*16 Y
*16 Pressure
*16 Const = 0x0000 (Xtilt)
*16 Const = 0x0000 (Ytilt)
*/
static __u8 g430sb_rdesc_fixed[] = {
0x05, 0x0D, // Usage Page (Digitizer)
0x09, 0x02, // Usage (Pen)
0xA1, 0x01, // Collection (Application)
0x85, 0x02, // Report ID (2) // First byte is always 0x02
0x09, 0x20, // Usage (Stylus)
0xA1, 0x00, // Collection (Physical)
// Second byte is 0xAx or 0xC0, A=1010b C=1100b, thus we use bits 0-2 for buttons,
// (bit order is: 7654 3210) skip bits 3 and 4, bit 5 = InRange, skip bits 6 and 7.
0x09, 0x42, // Usage (Tip Switch)
0x09, 0x44, // Usage (Barrel Switch / BS1)
0x09, 0x46, // Usage (Tablet Pick / BS2)
0x15, 0x00, // Logical Minimum (0)
0x25, 0x01, // Logical Maximum (1)
0x75, 0x01, // Report Size (1)
0x95, 0x03, // Report Count (3)
0x81, 0x02, // Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)

0x95, 0x02, // Report Count (2)
0x81, 0x03, // Input (Const,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)

0x09, 0x32, // Usage (In Range)
0x95, 0x01, // Report Count (1)
0x81, 0x02, // Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)

0x95, 0x02, // Report Count (2)
0x81, 0x03, // Input (Const,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
// Lmin, Lmax and RS are propagated up to this point

// The rest of report are 5 int16le numbers: X, Y, Pressure, Xtilt/Unused, Ytilt/Unused
// X and Y are in different usage page, Generic Desktop, so we save usage page
0xA4, // Push
0x05, 0x01, // Usage Page (Generic Desktop Ctrls)

0x09, 0x30, // Usage (X)
0x15, 0x00, // Logical Minimum (0)
0x26, 0xB0, 0x27, // Logical Maximum (10160)
0x65, 0x11, // Unit (System: SI Linear, Length: Centimeter)
0x55, 0x0D, // Unit Exponent (-3)
// Physical minimum and Maximum are approximately same as logical, since tablet area is 101x77mm
0x35, 0x00, // Physical Minimum (0)
0x46, 0xB0, 0x27, // Physical Maximum (10160)
0x75, 0x10, // Report Size (16)
0x95, 0x01, // Report Count (1)
0x81, 0x22, // Input (Data,Var,Abs,No Wrap,Linear,No Preferred State,No Null Position)

0x09, 0x31, // Usage (Y)
0x26, 0xC4, 0x1D, // Logical Maximum (7620)
0x46, 0xC4, 0x1D, // Physical Maximum (7620)
0x81, 0x22, // Input (Data,Var,Abs,No Wrap,Linear,No Preferred State,No Null Position)

// And then restore Usage Page before defining pen Pressure
0xB4, // Pop

0x09, 0x30, // Usage (Tip Pressure)
0x15, 0x00, // Logical Minimum (0)
0x26, 0xFF, 0x1F, // Logical Maximum (8191)
0x75, 0x10, // Report Size (16)
0x95, 0x01, // Report Count (1)
// This variable was with null state flag before
0x81, 0x02, // Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)

// The rest is unused so we define two 16-bit variables with no usage

0x95, 0x02, // Report Count (2)
0x81, 0x03, // Input (Const,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)

0xC0, // End Collection
0xC0, // End Collection
};

static __u8 *g430sb_report_fixup(struct hid_device *hdev, __u8 *rdesc,
unsigned int *rsize)
{
struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
if (intf->cur_altsetting->desc.bInterfaceNumber != G430SB_PEN_INTERFACE) {
/* Skip interfaces we don't need */
return 0;
}

if (*rsize == G430SB_RDESC_ORIG_SIZE) {
rdesc = g430sb_rdesc_fixed;
*rsize = sizeof(g430sb_rdesc_fixed);
hid_info(hdev, "Report descriptor fixed, new *rsize=%d, interface=%d\n", *rsize, intf->cur_altsetting->desc.bInterfaceNumber);
} else {
/* Should never happen now */
hid_info(hdev, "Report descriptor unchanged, because *rsize=%d, interface=%d\n", *rsize, intf->cur_altsetting->desc.bInterfaceNumber);
}

return rdesc;
}

static int g430sb_probe(struct hid_device *hdev,
const struct hid_device_id *id)
{
int rc;
__u8 g430sb_init_data[3] = {0x02, 0xB0, 0x04};
__u8 *init_data;
unsigned char endpoint = 0x03;
int bytes_transferred = 0;
int timeout = 1000;

/* Check arguments */
if (hdev == NULL) {
rc = -EINVAL;
return rc;
}

struct usb_device *udev = hid_to_usb_dev(hdev);
/* If we at wrong interface, exit early */
struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
if (intf->cur_altsetting->desc.bInterfaceNumber != G430SB_PEN_INTERFACE) {
hid_info(hdev, "Not a pen interface, disable.\n");
return -ENODEV;
}

/* We need to use kernel memory instead of stack to make the function below*/
init_data = kcalloc(sizeof(g430sb_init_data), 1, GFP_KERNEL);
if (init_data == NULL) {
hid_err(hdev, "failed to allocate memory\n");
rc = -ENOMEM;
goto cleanup;
}
memcpy(init_data, g430sb_init_data, sizeof(g430sb_init_data));


/* We need to send three bytes to G430S_B to switch it into native mode
*
* extern int usb_interrupt_msg(struct usb_device *usb_dev,
* unsigned int pipe,
* void *data,
* int len,
* int *actual_length,
* int timeout);
*/
rc = usb_interrupt_msg(udev, usb_sndintpipe(udev, endpoint), init_data, sizeof(g430sb_init_data), &bytes_transferred, timeout);
if (rc) {
hid_err(hdev, "init failed: rc:%d transferred:%d\n", rc, bytes_transferred);
goto cleanup;
} else {
hid_info(hdev, "init success:%d, %d bytes sent\n", rc, bytes_transferred);
}

rc = hid_parse(hdev);
if (rc) {
hid_err(hdev, "parse failed\n");
goto cleanup;
}

rc = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
if (rc) {
hid_err(hdev, "hw start failed\n");
goto cleanup;
}

rc = 0;
cleanup:
kfree(init_data);
return rc;
}

static const struct hid_device_id g430sb_devices[] = {
{ HID_USB_DEVICE(USB_VENDOR_ID_UGEE,
USB_DEVICE_ID_UGEE_XPPEN_TABLET_G430SB) },
{ }
};
MODULE_DEVICE_TABLE(hid, g430sb_devices);

static struct hid_driver g430sb_driver = {
.name = "g430sb",
.id_table = g430sb_devices,
.probe = g430sb_probe,
.report_fixup = g430sb_report_fixup,
};

module_hid_driver(g430sb_driver);

MODULE_LICENSE("GPL");