Quoting AngeloGioacchino Del Regno (2022-02-21 15:30:07)

Il 18/02/22 15:54, Guillaume Ranquet ha scritto:

quoted

From: Markus Schneider-Pargmann <msp@baylibre.com>

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@baylibre.com>
Signed-off-by: Guillaume Ranquet <redacted>
---
  drivers/video/hdmi.c        | 83 ++++++++++++++++++++++++++++---------
  include/drm/drm_dp_helper.h |  2 +
  include/linux/hdmi.h        |  7 +++-
  3 files changed, 72 insertions(+), 20 deletions(-)

diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
index 947be761dfa40..63e74d9fd210e 100644
--- a/drivers/video/hdmi.c
+++ b/drivers/video/hdmi.c

@@ -21,6 +21,7 @@
   * DEALINGS IN THE SOFTWARE.
   */

+#include <drm/drm_dp_helper.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 +486,44 @@ 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

This fits in one line (82 cols is ok)... but, anyway, please capitalize D and P
in the DisplayPort word.

Yeah, I ran clang-format and didn't want to contradict the tool :)
I'll fix that for v9

quoted

+ *
+ * @frame HDMI Audio infoframe

You're almost there! You missed a colon after each description.
Also, I personally like seeing indented descriptions as, in my opinion, this
enhances human readability, as it's a bit more pleasing to the eye... but
it's not a requirement, so you be the judge.

* @frame:      HDMI Audio infoframe
* @sdp:        Secondary data packet......
* @dp_version: DisplayPort version......

Please fix.

I completly forgot to generate and check the kerneldoc.
Sorry.

quoted

+ * @sdp secondary data packet for display port. This is filled with the
+ * appropriate data
+ * @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 the secondary data packet to be used for Display Port.
+ *
+ * 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

Please, C-style comments:

        /* Secondary-data packet header */

Thanks,
Angelo

I think this is not the only case of C++ comment that slipped past me...
I'll revise the whole series.

Thx,
Guillaume.