[RFC PATCH 4/5] video/hdmi: Add audio_infoframe packing for DP

[Markus Schneider-Pargmann]

Similar to HDMI, DP uses audio infoframes as well which are structured
very similar to the HDMI ones.

This patch adds a helper function to pack the HDMI audio infoframe for
DP, called hdmi_audio_infoframe_pack_for_dp().
hdmi_audio_infoframe_pack_only() is split into two parts. One of them
packs the payload only and can be used for HDMI and DP.

Signed-off-by: Markus Schneider-Pargmann <msp at baylibre.com>
---
 drivers/video/hdmi.c | 87 +++++++++++++++++++++++++++++++++++---------
 include/linux/hdmi.h |  4 ++
 2 files changed, 73 insertions(+), 18 deletions(-)

diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
index 947be761dfa4..59c4341549e4 100644
--- a/drivers/video/hdmi.c
+++ b/drivers/video/hdmi.c
@@ -387,6 +387,28 @@ int hdmi_audio_infoframe_check(struct hdmi_audio_infoframe *frame)
 }
 EXPORT_SYMBOL(hdmi_audio_infoframe_check);
 
+static void
+hdmi_audio_infoframe_pack_payload(const struct hdmi_audio_infoframe *frame,
+				  u8 *buffer)
+{
+	u8 channels;
+
+	if (frame->channels >= 2)
+		channels = frame->channels - 1;
+	else
+		channels = 0;
+
+	buffer[0] = ((frame->coding_type & 0xf) << 4) | (channels & 0x7);
+	buffer[1] = ((frame->sample_frequency & 0x7) << 2) |
+		 (frame->sample_size & 0x3);
+	buffer[2] = frame->coding_type_ext & 0x1f;
+	buffer[3] = frame->channel_allocation;
+	buffer[4] = (frame->level_shift_value & 0xf) << 3;
+
+	if (frame->downmix_inhibit)
+		buffer[4] |= BIT(7);
+}
+
 /**
  * hdmi_audio_infoframe_pack_only() - write HDMI audio infoframe to binary buffer
  * @frame: HDMI audio infoframe
@@ -404,7 +426,6 @@ EXPORT_SYMBOL(hdmi_audio_infoframe_check);
 ssize_t hdmi_audio_infoframe_pack_only(const struct hdmi_audio_infoframe *frame,
 				       void *buffer, size_t size)
 {
-	unsigned char channels;
 	u8 *ptr = buffer;
 	size_t length;
 	int ret;
@@ -420,28 +441,13 @@ ssize_t hdmi_audio_infoframe_pack_only(const struct hdmi_audio_infoframe *frame,
 
 	memset(buffer, 0, size);
 
-	if (frame->channels >= 2)
-		channels = frame->channels - 1;
-	else
-		channels = 0;
-
 	ptr[0] = frame->type;
 	ptr[1] = frame->version;
 	ptr[2] = frame->length;
 	ptr[3] = 0; /* checksum */
 
-	/* start infoframe payload */
-	ptr += HDMI_INFOFRAME_HEADER_SIZE;
-
-	ptr[0] = ((frame->coding_type & 0xf) << 4) | (channels & 0x7);
-	ptr[1] = ((frame->sample_frequency & 0x7) << 2) |
-		 (frame->sample_size & 0x3);
-	ptr[2] = frame->coding_type_ext & 0x1f;
-	ptr[3] = frame->channel_allocation;
-	ptr[4] = (frame->level_shift_value & 0xf) << 3;
-
-	if (frame->downmix_inhibit)
-		ptr[4] |= BIT(7);
+	hdmi_audio_infoframe_pack_payload(frame,
+					  ptr + HDMI_INFOFRAME_HEADER_SIZE);
 
 	hdmi_infoframe_set_checksum(buffer, length);
 
@@ -479,6 +485,51 @@ ssize_t hdmi_audio_infoframe_pack(struct hdmi_audio_infoframe *frame,
 }
 EXPORT_SYMBOL(hdmi_audio_infoframe_pack);
 
+/**
+ * hdmi_audio_infoframe_pack_for_dp - Pack a HDMI Audio infoframe for
+ *                                    displayport
+ *
+ * @frame HDMI Audio infoframe
+ * @header Header buffer to be used
+ * @header_size Size of header buffer
+ * @data Data buffer to be used
+ * @data_size Size of data buffer
+ * @dp_version Display Port version to be encoded in the header
+ *
+ * Packs a HDMI Audio Infoframe to be sent over Display Port. This function
+ * fills both header and data buffer with the required data.
+ *
+ * Return: Number of total written bytes or a negative errno on failure.
+ */
+ssize_t hdmi_audio_infoframe_pack_for_dp(struct hdmi_audio_infoframe *frame,
+					 void *header, size_t header_size,
+					 void *data, size_t data_size,
+					 u8 dp_version)
+{
+	int ret;
+	u8 *hdr_ptr = header;
+
+	ret = hdmi_audio_infoframe_check(frame);
+	if (ret)
+		return ret;
+
+	if (header_size < 4 || data_size < frame->length)
+		return -ENOSPC;
+
+	memset(header, 0, header_size);
+	memset(data, 0, data_size);
+
+	// Secondary-data packet header
+	hdr_ptr[1] = frame->type;
+	hdr_ptr[2] = 0x1B;  // As documented by DP spec for Secondary-data Packets
+	hdr_ptr[3] = (dp_version & 0x3f) << 2;
+
+	hdmi_audio_infoframe_pack_payload(frame, data);
+
+	return frame->length + 4;
+}
+EXPORT_SYMBOL(hdmi_audio_infoframe_pack_for_dp);
+
 /**
  * hdmi_vendor_infoframe_init() - initialize an HDMI vendor infoframe
  * @frame: HDMI vendor infoframe
diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
index c8ec982ff498..f576a0b08c85 100644
--- a/include/linux/hdmi.h
+++ b/include/linux/hdmi.h
@@ -334,6 +334,10 @@ struct hdmi_audio_infoframe {
 int hdmi_audio_infoframe_init(struct hdmi_audio_infoframe *frame);
 ssize_t hdmi_audio_infoframe_pack(struct hdmi_audio_infoframe *frame,
 				  void *buffer, size_t size);
+ssize_t hdmi_audio_infoframe_pack_for_dp(struct hdmi_audio_infoframe *frame,
+					 void *header, size_t header_size,
+					 void *data, size_t data_size,
+					 u8 dp_version);
 ssize_t hdmi_audio_infoframe_pack_only(const struct hdmi_audio_infoframe *frame,
 				       void *buffer, size_t size);
 int hdmi_audio_infoframe_check(struct hdmi_audio_infoframe *frame);
-- 
2.32.0