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Date: Wed, 19 Jul 2017 08:49:03 +0800
From: Chris Zhong <zyw@...k-chips.com>
To: Doug Anderson <dianders@...omium.org>
Cc: Sean Paul <seanpaul@...omium.org>,
Brian Norris <briannorris@...omium.org>,
"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
Mark yao <mark.yao@...k-chips.com>,
Heiko Stübner <heiko@...ech.de>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
Shashank Sharma <shashank.sharma@...el.com>,
Jose Abreu <joabreu@...opsys.com>,
Jani Nikula <jani.nikula@...el.com>,
Thierry Reding <treding@...dia.com>,
linux-fbdev@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] video/hdmi: Introduce helpers for the HDMI audio
infoframe payload
Hi Doug
On Tuesday, July 18, 2017 11:16 PM, Doug Anderson wrote:
> Hi,
>
> On Tue, Jul 18, 2017 at 4:20 AM, Chris Zhong <zyw@...k-chips.com> wrote:
>> The DP is using the same audio infoframe payload as hdmi, per DP 1.3
>> spec, but it has a different header. Provide a new interface here,
>> it just packs the payload.
>>
>> Signed-off-by: Chris Zhong <zyw@...k-chips.com>
>> ---
>>
>> Changes in v2: None
>>
>> drivers/video/hdmi.c | 66 ++++++++++++++++++++++++++++++++++++++--------------
>> include/linux/hdmi.h | 3 ++-
>> 2 files changed, 50 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
>> index 1cf907e..e0b041e 100644
>> --- a/drivers/video/hdmi.c
>> +++ b/drivers/video/hdmi.c
>> @@ -240,6 +240,49 @@ int hdmi_audio_infoframe_init(struct hdmi_audio_infoframe *frame)
>> EXPORT_SYMBOL(hdmi_audio_infoframe_init);
>>
>> /**
>> + * hdmi_audio_infoframe_pack_payload() - write HDMI audio infoframe payload to
>> + * binary buffer
>> + * @frame: HDMI audio infoframe
>> + * @buffer: destination buffer
>> + * @size: size of buffer
>> + *
>> + * Packs the information contained in the @frame structure into a binary
>> + * representation that can be written into the corresponding controller
>> + * registers.
>> + *
>> + * Returns 0 on success or a negative error code on failure.
>> + */
>> +ssize_t hdmi_audio_infoframe_pack_payload(struct hdmi_audio_infoframe *frame,
>> + void *buffer, size_t size)
>> +{
>> + unsigned char channels;
>> + u8 *ptr = buffer;
>> +
>> + if (size < frame->length)
> You also need to return -ENOSPC if (size < 5). That's because below
> you always write 5 elements into this array. I'll leave it to someone
> with actual DRM experience to say whether they want a #define of some
> sort here. Probably they do since someone made a #define for
> "HDMI_INFOFRAME_HEADER_SIZE".
>
> Also: you don't use frame->length anywhere in this function and it
> doesn't seem to be related with packing the payload. Seems like you
> shouldn't check it here.
Actually, I think it should be "if (size < HDMI_AUDIO_INFOFRAME_SIZE)"
>
>
>> + return -ENOSPC;
>> +
>> + memset(buffer, 0, size);
> I don't think the memset belongs here. It seems like all this
> function is doing is setting up ptr[0] through ptr[4] and the memset()
> doesn't belong with that, does it?
>
I think the length of payload is 10 Bytes(DB1~DB10), per audio infoframe
Format,
but we only use the front 5 Bytes, the back 5 bytes must be 0. If we
take the 10
bytes as a whole, it make sense.
>> @@ -256,22 +299,15 @@ EXPORT_SYMBOL(hdmi_audio_infoframe_init);
>> ssize_t hdmi_audio_infoframe_pack(struct hdmi_audio_infoframe *frame,
>> void *buffer, size_t size)
>> {
>> - unsigned char channels;
>> u8 *ptr = buffer;
>> size_t length;
>> + int ret;
>>
>> length = HDMI_INFOFRAME_HEADER_SIZE + frame->length;
>>
>> if (size < length)
>> return -ENOSPC;
>>
>> - memset(buffer, 0, size);
> It seems like the memset() belongs here, logically. This function
> deals with the whole buffer so it should be clearing it.
>
>> -
>> - if (frame->channels >= 2)
>> - channels = frame->channels - 1;
>> - else
>> - channels = 0;
>> -
>> ptr[0] = frame->type;
>> ptr[1] = frame->version;
>> ptr[2] = frame->length;
>> @@ -279,16 +315,10 @@ ssize_t hdmi_audio_infoframe_pack(struct hdmi_audio_infoframe *frame,
>>
>> /* 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);
>> + ret = hdmi_audio_infoframe_pack_payload(frame, ptr,
>> + size - HDMI_INFOFRAME_HEADER_SIZE);
>> + if (ret)
>> + return ret;
>>
>> hdmi_infoframe_set_checksum(buffer, length);
>>
>> diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
>> index d271ff2..d93c709 100644
>> --- a/include/linux/hdmi.h
>> +++ b/include/linux/hdmi.h
>> @@ -272,7 +272,8 @@ 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_payload(struct hdmi_audio_infoframe *frame,
>> + void *buffer, size_t size);
> nit: seems like you're changing whitespace here (there used to be a
> blank line before the enum).
>
>> enum hdmi_3d_structure {
>> HDMI_3D_STRUCTURE_INVALID = -1,
>> HDMI_3D_STRUCTURE_FRAME_PACKING = 0,
>> --
>> 2.7.4
>>
>
>
--
Chris Zhong
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