Re: [RFC 1/4] ASoC: topology: Add topology UAPI header.

[Liam Girdwood <liam.r.girdwood@linux.intel.com>]

On Mon, 2015-04-20 at 22:30 +0100, Mark Brown wrote:
> On Thu, Apr 16, 2015 at 09:48:15PM +0100, Liam Girdwood wrote:
> 
> > +struct snd_soc_tplg_hdr {
> > +	__le32 magic;
> > +	__le32 abi;		/* ABI version */
> > +	__le32 version;		/* optional vendor specific version details */
> > +	__le32 type;		/* SND_SOC_TPLG_ */
> > +	__le32 vendor_type;	/* optional vendor specific type info */
> > +	__le32 size;		/* data bytes, excluding this header */
> > +	__le32 id;		/* identifier for block */
> > +	char reserved[128];
> > +} __attribute__((packed));
> 
> Not got a massively strong opinion here but given that we have ABI
> versioning can we just skip the 128 bytes of reserved space in most of
> the structs?  Doesn't seem to be doing much except making the files
> bigger.

We had a similar discussion in Nuremburg last week, the intention is to
keep the size of the structures constant so wont dont break older
kernels with newer userspace ABIs etc.

> 
> > +/*
> > + * Mixer kcontrol.
> > + */
> > +struct snd_soc_tplg_mixer_control {
> > +	struct snd_soc_tplg_control_hdr hdr;
> > +	__le32 min;
> > +	__le32 max;
> > +	__le32 platform_max;
> > +	__le32 reg;
> > +	__le32 rreg;
> > +	__le32 shift;
> > +	__le32 rshift;
> 
> Do we want to convert this into an array of reg/shift tuples for the
> (dobutless forthcoming) 5.1 controls?  Not sure it's worth it.  I do
> think we probably need some explicit documentation for things like what
> to do with the left and right bits, I guess we hope other OSs or
> whatever can make use of the same topology if we're trying to make it
> standard.

Yeah, that's a good point which we should address :)

What about something like :-

struct snd_soc_mixer_channel {
	__le32 reg;
	__le32 shift;
}

struct snd_soc_tplg_mixer_control {
	struct snd_soc_tplg_control_hdr hdr;
	__le32 min;
	__le32 max;
	__le32 platform_max;
	__le32 invert;
	__le32 num_channels;
	char reserved[64];
	struct snd_soc_tplg_mixer_channel channel[0];
	struct snd_soc_tplg_private priv;
} __attribute__((packed));

The same could be applied to the other control types too ?

Liam

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