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From:   Guillaume Ranquet <granquet@baylibre.com>
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Date:   Fri, 25 Feb 2022 02:38:47 -0800
Message-ID: <CABnWg9v-gamMoex-CSLY9uOPKbcm3dBDvYLSRX9LHuhYua=wDQ@mail.gmail.com>
Subject: Re: [PATCH v8 04/19] video/hdmi: Add audio_infoframe packing for DP
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>, airlied@linux.ie,
        chunfeng.yun@mediatek.com, chunkuang.hu@kernel.org,
        ck.hu@mediatek.com, daniel@ffwll.ch, deller@gmx.de,
        jitao.shi@mediatek.com, kishon@ti.com,
        maarten.lankhorst@linux.intel.com, matthias.bgg@gmail.com,
        mripard@kernel.org, p.zabel@pengutronix.de, robh+dt@kernel.org,
        tzimmermann@suse.de, vkoul@kernel.org
Cc:     dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-phy@lists.infradead.org, linux-fbdev@vger.kernel.org,
        Markus Schneider-Pargmann <msp@baylibre.com>
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Quoting AngeloGioacchino Del Regno (2022-02-21 15:30:07)
> Il 18/02/22 15:54, Guillaume Ranquet ha scritto:
> > 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 <granquet@baylibre.com>
> > ---
> >   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

> > + *
> > + * @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.

> > + * @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.