[PATCH 04/18] HID: bpf: add in-tree HID-BPF fix for the HP Elite Presenter Mouse

[Benjamin Tissoires <bentiss@kernel.org>]

Duplicate of commit 0db117359e47 ("HID: add quirk for 03f0:464a HP Elite
Presenter Mouse"), but in a slightly better way.

This time we actually change the application collection, making clearer
for userspace what the second mouse is.

Note that having both hid-quirks fix and this HID-BPF fix is not a
problem at all.

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
---
 drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c | 58 +++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c b/drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c
new file mode 100644
index 000000000000..3d14bbb6f276
--- /dev/null
+++ b/drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2023 Benjamin Tissoires
+ */
+
+#include "vmlinux.h"
+#include "hid_bpf.h"
+#include "hid_bpf_helpers.h"
+#include <bpf/bpf_tracing.h>
+
+#define VID_HP 0x03F0
+#define PID_ELITE_PRESENTER 0x464A
+
+HID_BPF_CONFIG(
+	HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_GENERIC, VID_HP, PID_ELITE_PRESENTER)
+);
+
+/*
+ * Already fixed as of commit 0db117359e47 ("HID: add quirk for 03f0:464a
+ * HP Elite Presenter Mouse") in the kernel, but this is a slightly better
+ * fix.
+ *
+ * The HP Elite Presenter Mouse HID Record Descriptor shows
+ * two mice (Report ID 0x1 and 0x2), one keypad (Report ID 0x5),
+ * two Consumer Controls (Report IDs 0x6 and 0x3).
+ * Prior to these fixes it registers one mouse, one keypad
+ * and one Consumer Control, and it was usable only as a
+ * digital laser pointer (one of the two mouses).
+ * We replace the second mouse collection with a pointer collection,
+ * allowing to use the device both as a mouse and a digital laser
+ * pointer.
+ */
+
+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 */
+
+	/* replace application mouse by application pointer on the second collection */
+	if (data[79] == 0x02)
+		data[79] = 0x01;
+
+	return 0;
+}
+
+SEC("syscall")
+int probe(struct hid_bpf_probe_args *ctx)
+{
+	ctx->retval = ctx->rdesc_size != 264;
+	if (ctx->retval)
+		ctx->retval = -EINVAL;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

-- 
2.44.0