linux-kernel - Re: [PATCH v8 04/19] video/hdmi: Add audio

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Message-ID: <a7605c9f-55f9-c7cc-f2b9-89ddbffb4927@collabora.com>
Date:   Mon, 21 Feb 2022 15:30:07 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Guillaume Ranquet <granquet@...libre.com>, chunkuang.hu@...nel.org,
        p.zabel@...gutronix.de, airlied@...ux.ie, daniel@...ll.ch,
        robh+dt@...nel.org, maarten.lankhorst@...ux.intel.com,
        mripard@...nel.org, tzimmermann@...e.de, matthias.bgg@...il.com,
        chunfeng.yun@...iatek.com, kishon@...com, vkoul@...nel.org,
        deller@....de, ck.hu@...iatek.com, jitao.shi@...iatek.com
Cc:     dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-phy@...ts.infradead.org, linux-fbdev@...r.kernel.org,
        Markus Schneider-Pargmann <msp@...libre.com>
Subject: Re: [PATCH v8 04/19] video/hdmi: Add audio_infoframe packing for DP

Il 18/02/22 15:54, Guillaume Ranquet ha scritto:
> From: Markus Schneider-Pargmann <msp@...libre.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@...libre.com>
> Signed-off-by: Guillaume Ranquet <granquet@...libre.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.

> + *
> + * @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.

> + * @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