Re: [Xen-devel] [PATCH v3] sndif: add ABI for Para-virtual sound

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.01.15 at 10:56, <oleksandr.dmytryshyn@xxxxxxxxxxxxxxx> wrote:
> +/*
> + * PCM FORMATS
> + *
> + * XENSND_PCM_FORMAT_<format>[_<endian>]
> + *
> + * format: <S/U/FLOAT>[<bits>] or <name>
> + *     S - signed, U - unsigned, FLOAT - float
> + *     bits - 8, 16, 24, 32 or absent
> + *     name - MU_LAW, GSM, etc.
> + *
> + * endian: <LE/BE>, may be absent
> + *     LE - Little endian, BE - Big endian
> + */
> +#define XENSND_PCM_FORMAT_S8            0
> +#define XENSND_PCM_FORMAT_U8            1
> +#define XENSND_PCM_FORMAT_S16_LE        2
> +#define XENSND_PCM_FORMAT_S16_BE        3
> +#define XENSND_PCM_FORMAT_U16_LE        4
> +#define XENSND_PCM_FORMAT_U16_BE        5
> +#define XENSND_PCM_FORMAT_S24_LE        6
> +#define XENSND_PCM_FORMAT_S24_BE        7
> +#define XENSND_PCM_FORMAT_U24_LE        8
> +#define XENSND_PCM_FORMAT_U24_BE        9
> +#define XENSND_PCM_FORMAT_S32_LE        10
> +#define XENSND_PCM_FORMAT_S32_BE        11
> +#define XENSND_PCM_FORMAT_U32_LE        12
> +#define XENSND_PCM_FORMAT_U32_BE        13
> +#define XENSND_PCM_FORMAT_FLOAT_LE      14 /* 4-byte float, IEEE-754 32-bit, 
> */
> +#define XENSND_PCM_FORMAT_FLOAT_BE      15 /* range -1.0 to 1.0              
> */

I think these should carry 32 in their names. I also wonder why
it needs to be FLOAT instead of just F.

> + * Request open - open an pcm stream for playback or capture:
> + *     0    1     2     3     4     5     6     7  octet
> + * +-----+-----+-----+-----+-----+-----+-----+-----+
> + * |       operation       |       stream_id       |
> + * +-----+-----+-----+-----+-----+-----+-----+-----+
> + * |      pcm_format       |      pcm_channes      |

pcm_channel(s)?

> + * All responce packets have the same length (76 bytes)

response

> + * Responce for all requests exept the XENSND_GET_VOLUME:
> + *     0    1     2     3     4     5     6     7  octet
> + * +-----+-----+-----+-----+-----+-----+-----+-----+
> + * |       stream_id       |       operation       |

Is there a really need for echoing the operation, i.e. isn't the echoed
ID sufficient? Because if you'd be able to drop this, request and
response sizes would match up, avoiding wasted space on the
shared page(s).

> + * +-----+-----+-----+-----+-----+-----+-----+-----+
Jan


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