video/hdmi: Add audio_infoframe packing for DP

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.

Also constify the frame parameter in hdmi_audio_infoframe_check() as
it is passed to hdmi_audio_infoframe_check_only() which expects a const.
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220901044149.16782-3-rex-bc.chen@mediatek.com

drivers/video/hdmi.c

@@ -21,6 +21,7 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include <drm/display/drm_dp.h>
 #include <linux/bitops.h>
 #include <linux/bug.h>
 #include <linux/errno.h>
@@ -381,12 +382,34 @@ static int hdmi_audio_infoframe_check_only(const struct hdmi_audio_infoframe *fr
  *
  * Returns 0 on success or a negative error code on failure.
  */
-int hdmi_audio_infoframe_check(struct hdmi_audio_infoframe *frame)
+int hdmi_audio_infoframe_check(const struct hdmi_audio_infoframe *frame)
 {
 	return hdmi_audio_infoframe_check_only(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 +427,6 @@ 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 +442,13 @@ 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 +486,43 @@ 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
+ * @sdp:        Secondary data packet for DisplayPort.
+ * @dp_version: DisplayPort version to be encoded in the header
+ *
+ * Packs a HDMI Audio Infoframe to be sent over DisplayPort. This function
+ * fills the secondary data packet to be used for DisplayPort.
+ *
+ * Return: Number of total written bytes or a negative errno on failure.
+ */
+ssize_t
+hdmi_audio_infoframe_pack_for_dp(const struct hdmi_audio_infoframe *frame,
+				 struct dp_sdp *sdp, u8 dp_version)
+{
+	int ret;
+
+	ret = hdmi_audio_infoframe_check(frame);
+	if (ret)
+		return ret;
+
+	memset(sdp->db, 0, sizeof(sdp->db));
+
+	/* Secondary-data packet header */
+	sdp->sdp_header.HB0 = 0;
+	sdp->sdp_header.HB1 = frame->type;
+	sdp->sdp_header.HB2 = DP_SDP_AUDIO_INFOFRAME_HB2;
+	sdp->sdp_header.HB3 = (dp_version & 0x3f) << 2;
+
+	hdmi_audio_infoframe_pack_payload(frame, sdp->db);
+
+	/* Return size =  frame length + four HB for sdp_header */
+	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

include/drm/display/drm_dp.h

@@ -1536,6 +1536,8 @@ enum drm_dp_phy {
 #define DP_SDP_VSC_EXT_CEA		0x21 /* DP 1.4 */
 /* 0x80+ CEA-861 infoframe types */
 
+#define DP_SDP_AUDIO_INFOFRAME_HB2	0x1b
+
 /**
  * struct dp_sdp_header - DP secondary data packet header
  * @HB0: Secondary Data Packet ID

include/linux/hdmi.h

@@ -336,7 +336,12 @@ ssize_t hdmi_audio_infoframe_pack(struct hdmi_audio_infoframe *frame,
 				  void *buffer, size_t size);
 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);
+int hdmi_audio_infoframe_check(const struct hdmi_audio_infoframe *frame);
+
+struct dp_sdp;
+ssize_t
+hdmi_audio_infoframe_pack_for_dp(const struct hdmi_audio_infoframe *frame,
+				 struct dp_sdp *sdp, u8 dp_version);
 
 enum hdmi_3d_structure {
 	HDMI_3D_STRUCTURE_INVALID = -1,