keytable: add bpf protocols

Add a few BPF protocols and infrastructure for building them.

Signed-off-by: Sean Young <sean@mess.org>

1 files changed, 126 insertions, 0 deletions

diff --git a/utils/keytable/bpf_protocols/grundig.c b/utils/keytable/bpf_protocols/grundig.c
new file mode 100644
index 00000000..4d8cc4b9
--- /dev/null
+++ b/utils/keytable/bpf_protocols/grundig.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright (C) 2018 Sean Young <sean@mess.org>
+
+#include <linux/lirc.h>
+#include <linux/bpf.h>
+
+#include "bpf_helpers.h"
+
+enum grundig_state {
+	STATE_INACTIVE,
+	STATE_HEADER_SPACE,
+	STATE_LEADING_PULSE,
+	STATE_BITS_SPACE,
+	STATE_BITS_PULSE,
+};
+
+struct decoder_state {
+	unsigned int bits;
+	enum grundig_state state;
+	unsigned int count;
+	unsigned int last_space;
+};
+
+struct bpf_map_def SEC("maps") decoder_state_map = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(unsigned int),
+	.value_size = sizeof(struct decoder_state),
+	.max_entries = 1,
+};
+
+static inline int eq_margin(unsigned d1, unsigned d2, unsigned margin)
+{
+	return ((d1 > (d2 - margin)) && (d1 < (d2 + margin)));
+}
+
+// These values can be overridden in the rc_keymap toml
+//
+// We abuse elf relocations. We cast the address of these variables to
+// an int, so that the compiler emits a mov immediate for the address
+// but uses it as an int. The bpf loader replaces the relocation with the
+// actual value (either overridden or taken from the data segment).
+int header_pulse = 900;
+int header_space = 2900;
+int leader_pulse = 1300;
+
+#define BPF_PARAM(x) (int)(&(x))
+
+SEC("grundig")
+int bpf_decoder(unsigned int *sample)
+{
+	unsigned int key = 0;
+	struct decoder_state *s = bpf_map_lookup_elem(&decoder_state_map, &key);
+
+	if (!s)
+		return 0;
+
+	switch (*sample & LIRC_MODE2_MASK) {
+	case LIRC_MODE2_SPACE:
+	case LIRC_MODE2_PULSE:
+	case LIRC_MODE2_TIMEOUT:
+		break;
+	default:
+		// not a timing events
+		return 0;
+	}
+
+	int duration = LIRC_VALUE(*sample);
+
+	if (s->state == STATE_INACTIVE) {
+		if (LIRC_IS_PULSE(*sample) && eq_margin(BPF_PARAM(header_pulse), duration, 100)) {
+			s->bits = 0;
+			s->state = STATE_HEADER_SPACE;
+			s->count = 0;
+		}
+	} else if (s->state == STATE_HEADER_SPACE) {
+		if (LIRC_IS_SPACE(*sample) && eq_margin(BPF_PARAM(header_space), duration, 200))
+			s->state = STATE_LEADING_PULSE;
+		else
+			s->state = STATE_INACTIVE;
+	} else if (s->state == STATE_LEADING_PULSE) {
+		if (LIRC_IS_PULSE(*sample) && eq_margin(BPF_PARAM(leader_pulse), duration, 100))
+			s->state = STATE_BITS_SPACE;
+		else
+			s->state = STATE_INACTIVE;
+	} else if (s->state == STATE_BITS_SPACE) {
+		s->last_space = duration;
+		s->state = STATE_BITS_PULSE;
+	} else if (s->state == STATE_BITS_PULSE) {
+		int t = -1;
+		if (eq_margin(s->last_space, (472), (150)) &&
+		    eq_margin(duration, (583), (150)))
+			t = 0;
+		if (eq_margin(s->last_space, (1139), (150)) &&
+		    eq_margin(duration, (583), (150)))
+			t = 1;
+		if (eq_margin(s->last_space, (1806), (150)) &&
+		    eq_margin(duration, (583), (150)))
+			t = 2;
+		if (eq_margin(s->last_space, (2200), (150)) &&
+		    eq_margin(duration, (1139), (150)))
+			t = 3;
+		if (t < 0) {
+			s->state = STATE_INACTIVE;
+		} else {
+			s->bits <<= 2;
+			switch (t) {
+			case 3: s->bits |= 0; break;
+			case 2: s->bits |= 3; break;
+			case 1: s->bits |= 2; break;
+			case 0: s->bits |= 1; break;
+			}
+			s->count += 2;
+			if (s->count == 16) {
+				bpf_rc_keydown(sample, 0x40, s->bits, 0);
+				s->state = STATE_INACTIVE;
+			} else {
+				s->state = STATE_BITS_SPACE;
+			}
+		}
+	}
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";