When using the XBox Wireless Controller Elite 2 over Bluetooth, the device exports the paddle on the back of the device as a single bitfield value of usage "Assign Selection".
The kernel doesn't process those usages properly and report KEY_UNKNOWN for it.
SDL doesn't know how to interprete that KEY_UNKNOWN and thus ignores the paddles.
Given that over USB the kernel uses BTN_TRIGGER_HAPPY[5-8], we can tweak the report descriptor to make the kernel interprete it properly: - we need an application collection of gamepad (so we have to close the current Consumer Control one) - we need to change the usage to be buttons from 0x15 to 0x18
Signed-off-by: Benjamin Tissoires bentiss@kernel.org --- .../hid/bpf/progs/Microsoft__XBox-Elite-2.bpf.c | 133 +++++++++++++++++++++ 1 file changed, 133 insertions(+)
diff --git a/drivers/hid/bpf/progs/Microsoft__XBox-Elite-2.bpf.c b/drivers/hid/bpf/progs/Microsoft__XBox-Elite-2.bpf.c new file mode 100644 index 000000000000..c04abecab8ee --- /dev/null +++ b/drivers/hid/bpf/progs/Microsoft__XBox-Elite-2.bpf.c @@ -0,0 +1,133 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2024 Benjamin Tissoires + */ + +#include "vmlinux.h" +#include "hid_bpf.h" +#include "hid_bpf_helpers.h" +#include <bpf/bpf_tracing.h> + +#define VID_MICROSOFT 0x045e +#define PID_XBOX_ELITE_2 0x0b22 + +HID_BPF_CONFIG( + HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_GENERIC, VID_MICROSOFT, PID_XBOX_ELITE_2) +); + +/* + * When using the XBox Wireless Controller Elite 2 over Bluetooth, + * the device exports the paddle on the back of the device as a single + * bitfield value of usage "Assign Selection". + * + * The kernel doesn't process those usages properly and report KEY_UNKNOWN + * for it. + * + * SDL doesn't know how to interprete that KEY_UNKNOWN and thus ignores the paddles. + * + * Given that over USB the kernel uses BTN_TRIGGER_HAPPY[5-8], we + * can tweak the report descriptor to make the kernel interprete it properly: + * - we need an application collection of gamepad (so we have to close the current + * Consumer Control one) + * - we need to change the usage to be buttons from 0x15 to 0x18 + */ + +#define OFFSET_ASSIGN_SELECTION 211 +#define ORIGINAL_RDESC_SIZE 464 + +const __u8 rdesc_assign_selection[] = { + 0x0a, 0x99, 0x00, // Usage (Media Select Security) 211 + 0x15, 0x00, // Logical Minimum (0) 214 + 0x26, 0xff, 0x00, // Logical Maximum (255) 216 + 0x95, 0x01, // Report Count (1) 219 + 0x75, 0x04, // Report Size (4) 221 + 0x81, 0x02, // Input (Data,Var,Abs) 223 + 0x15, 0x00, // Logical Minimum (0) 225 + 0x25, 0x00, // Logical Maximum (0) 227 + 0x95, 0x01, // Report Count (1) 229 + 0x75, 0x04, // Report Size (4) 231 + 0x81, 0x03, // Input (Cnst,Var,Abs) 233 + 0x0a, 0x81, 0x00, // Usage (Assign Selection) 235 + 0x15, 0x00, // Logical Minimum (0) 238 + 0x26, 0xff, 0x00, // Logical Maximum (255) 240 + 0x95, 0x01, // Report Count (1) 243 + 0x75, 0x04, // Report Size (4) 245 + 0x81, 0x02, // Input (Data,Var,Abs) 247 +}; + +/* + * we replace the above report descriptor extract + * with the one below. + * To make things equal in size, we take out a larger + * portion than just the "Assign Selection" range, because + * we need to insert a new application collection to force + * the kernel to use BTN_TRIGGER_HAPPY[4-7]. + */ +const __u8 fixed_rdesc_assign_selection[] = { + 0x0a, 0x99, 0x00, // Usage (Media Select Security) 211 + 0x15, 0x00, // Logical Minimum (0) 214 + 0x26, 0xff, 0x00, // Logical Maximum (255) 216 + 0x95, 0x01, // Report Count (1) 219 + 0x75, 0x04, // Report Size (4) 221 + 0x81, 0x02, // Input (Data,Var,Abs) 223 + /* 0x15, 0x00, */ // Logical Minimum (0) ignored + 0x25, 0x01, // Logical Maximum (1) 225 + 0x95, 0x04, // Report Count (4) 227 + 0x75, 0x01, // Report Size (1) 229 + 0x81, 0x03, // Input (Cnst,Var,Abs) 231 + 0xc0, // End Collection 233 + 0x05, 0x01, // Usage Page (Generic Desktop) 234 + 0x0a, 0x05, 0x00, // Usage (Game Pad) 236 + 0xa1, 0x01, // Collection (Application) 239 + 0x05, 0x09, // Usage Page (Button) 241 + 0x19, 0x15, // Usage Minimum (21) 243 + 0x29, 0x18, // Usage Maximum (24) 245 + /* 0x15, 0x00, */ // Logical Minimum (0) ignored + /* 0x25, 0x01, */ // Logical Maximum (1) ignored + /* 0x95, 0x01, */ // Report Size (1) ignored + /* 0x75, 0x04, */ // Report Count (4) ignored + 0x81, 0x02, // Input (Data,Var,Abs) 247 +}; + +_Static_assert(sizeof(rdesc_assign_selection) == sizeof(fixed_rdesc_assign_selection), + "Rdesc and fixed rdesc of different size"); +_Static_assert(sizeof(rdesc_assign_selection) + OFFSET_ASSIGN_SELECTION < ORIGINAL_RDESC_SIZE, + "Rdesc at given offset is too big"); + +SEC("fmod_ret/hid_bpf_rdesc_fixup") +int BPF_PROG(hid_fix_rdesc, struct hid_bpf_ctx *hctx) +{ + __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */); + + if (!data) + return 0; /* EPERM check */ + + /* Check that the device is compatible */ + if (__builtin_memcmp(data + OFFSET_ASSIGN_SELECTION, + rdesc_assign_selection, + sizeof(rdesc_assign_selection))) + return 0; + + __builtin_memcpy(data + OFFSET_ASSIGN_SELECTION, + fixed_rdesc_assign_selection, + sizeof(fixed_rdesc_assign_selection)); + + return 0; +} + +SEC("syscall") +int probe(struct hid_bpf_probe_args *ctx) +{ + /* only bind to the keyboard interface */ + ctx->retval = ctx->rdesc_size != ORIGINAL_RDESC_SIZE; + if (ctx->retval) + ctx->retval = -EINVAL; + + if (__builtin_memcmp(ctx->rdesc + OFFSET_ASSIGN_SELECTION, + rdesc_assign_selection, + sizeof(rdesc_assign_selection))) + ctx->retval = -EINVAL; + + return 0; +} + +char _license[] SEC("license") = "GPL";