Re: [PATCH v2 1/2] video/hdmi: Introduce helpers for the HDMI audio infoframe payload

2017-07-19 Thread Doug Anderson 
Hi

On Tue, Jul 18, 2017 at 5:49 PM, Chris Zhong  wrote:
> 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  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 
>>> ---
>>>
>>> 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)"

Ah, OK.  My main point was that this function needed to make sense on
its own.  ...and the function in your patch writes to [0] through [4]
without actually confirming that there are at least 5 elements.  I'd
be OK with:

  if ((size < frame->length || 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.

OK, memset() here makes sense with what you say about the frame
needing to be 10 bytes big.

-Doug

Re: [PATCH v2 1/2] video/hdmi: Introduce helpers for the HDMI audio infoframe payload

2017-07-19 Thread Doug Anderson 
Hi

On Tue, Jul 18, 2017 at 5:49 PM, Chris Zhong  wrote:
> 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  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 
>>> ---
>>>
>>> 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)"

Ah, OK.  My main point was that this function needed to make sense on
its own.  ...and the function in your patch writes to [0] through [4]
without actually confirming that there are at least 5 elements.  I'd
be OK with:

  if ((size < frame->length || 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.

OK, memset() here makes sense with what you say about the frame
needing to be 10 bytes big.

-Doug

Re: [PATCH v2 1/2] video/hdmi: Introduce helpers for the HDMI audio infoframe payload

2017-07-18 Thread Chris Zhong 

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  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 
---

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

Re: [PATCH v2 1/2] video/hdmi: Introduce helpers for the HDMI audio infoframe payload

2017-07-18 Thread Chris Zhong 

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  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 
---

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

Re: [PATCH v2 1/2] video/hdmi: Introduce helpers for the HDMI audio infoframe payload

2017-07-18 Thread Doug Anderson 
Hi,

On Tue, Jul 18, 2017 at 4:20 AM, Chris Zhong  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 
> ---
>
> 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.


> +   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?


> @@ -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
>

Re: [PATCH v2 1/2] video/hdmi: Introduce helpers for the HDMI audio infoframe payload

2017-07-18 Thread Doug Anderson 
Hi,

On Tue, Jul 18, 2017 at 4:20 AM, Chris Zhong  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 
> ---
>
> 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.


> +   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?


> @@ -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
>