[media] rc: ir-nec-decoder: Add encode capability

Add the capability to encode NEC scancodes as raw events. The
scancode_to_raw is pretty much taken from the img-ir NEC filter()
callback, and modulation uses the pulse distance helper added in a
previous commit.
Signed-off-by: James Hogan <james@albanarts.com>
Signed-off-by: Sean Young <sean@mess.org>
Cc: Antti Seppälä <a.seppala@gmail.com>
Cc: David Härdeman <david@hardeman.nu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/rc/ir-nec-decoder.c

@@ -204,9 +204,90 @@ static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
 	return -EINVAL;
 }
 
+/**
+ * ir_nec_scancode_to_raw() - encode an NEC scancode ready for modulation.
+ * @protocol:	specific protocol to use
+ * @scancode:	a single NEC scancode.
+ * @raw:	raw data to be modulated.
+ */
+static u32 ir_nec_scancode_to_raw(enum rc_type protocol, u32 scancode)
+{
+	unsigned int addr, addr_inv, data, data_inv;
+
+	data = scancode & 0xff;
+
+	if (protocol == RC_TYPE_NEC32) {
+		/* 32-bit NEC (used by Apple and TiVo remotes) */
+		/* scan encoding: aaAAddDD */
+		addr_inv   = (scancode >> 24) & 0xff;
+		addr       = (scancode >> 16) & 0xff;
+		data_inv   = (scancode >>  8) & 0xff;
+	} else if (protocol == RC_TYPE_NECX) {
+		/* Extended NEC */
+		/* scan encoding AAaaDD */
+		addr       = (scancode >> 16) & 0xff;
+		addr_inv   = (scancode >>  8) & 0xff;
+		data_inv   = data ^ 0xff;
+	} else {
+		/* Normal NEC */
+		/* scan encoding: AADD */
+		addr       = (scancode >>  8) & 0xff;
+		addr_inv   = addr ^ 0xff;
+		data_inv   = data ^ 0xff;
+	}
+
+	/* raw encoding: ddDDaaAA */
+	return data_inv << 24 |
+	       data     << 16 |
+	       addr_inv <<  8 |
+	       addr;
+}
+
+static const struct ir_raw_timings_pd ir_nec_timings = {
+	.header_pulse	= NEC_HEADER_PULSE,
+	.header_space	= NEC_HEADER_SPACE,
+	.bit_pulse	= NEC_BIT_PULSE,
+	.bit_space[0]	= NEC_BIT_0_SPACE,
+	.bit_space[1]	= NEC_BIT_1_SPACE,
+	.trailer_pulse	= NEC_TRAILER_PULSE,
+	.trailer_space	= NEC_TRAILER_SPACE,
+	.msb_first	= 0,
+};
+
+/**
+ * ir_nec_encode() - Encode a scancode as a stream of raw events
+ *
+ * @protocol:	protocol to encode
+ * @scancode:	scancode to encode
+ * @events:	array of raw ir events to write into
+ * @max:	maximum size of @events
+ *
+ * Returns:	The number of events written.
+ *		-ENOBUFS if there isn't enough space in the array to fit the
+ *		encoding. In this case all @max events will have been written.
+ */
+static int ir_nec_encode(enum rc_type protocol, u32 scancode,
+			 struct ir_raw_event *events, unsigned int max)
+{
+	struct ir_raw_event *e = events;
+	int ret;
+	u32 raw;
+
+	/* Convert a NEC scancode to raw NEC data */
+	raw = ir_nec_scancode_to_raw(protocol, scancode);
+
+	/* Modulate the raw data using a pulse distance modulation */
+	ret = ir_raw_gen_pd(&e, max, &ir_nec_timings, NEC_NBITS, raw);
+	if (ret < 0)
+		return ret;
+
+	return e - events;
+}
+
 static struct ir_raw_handler nec_handler = {
 	.protocols	= RC_BIT_NEC | RC_BIT_NECX | RC_BIT_NEC32,
 	.decode		= ir_nec_decode,
+	.encode		= ir_nec_encode,
 };
 
 static int __init ir_nec_decode_init(void)