This commit adds a new framing mode that frames all MIDI data into 32-byte frames with a timestamp. The main benefit is that we can get accurate timestamps even if userspace wakeup and processing is not immediate. Testing on a Celeron N3150 with this mode has a max jitter of 2.8 ms, compared to the in-kernel seq implementation which has a max jitter of 5 ms during idle and much worse when running scheduler stress tests in parallel.
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| @@ -710,7 +710,7 @@ enum { · 709 unmodified lines | ||
| 710 | 710 | * Raw MIDI section - /dev/snd/midi?? |
| 711 | 711 | */ |
| 712 | 712 | |
| 713 | −#define SNDRV_RAWMIDI_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 1) | |
| 713 | +#define SNDRV_RAWMIDI_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 2) | |
| 714 | 714 | |
| 715 | 715 | enum { |
| 716 | 716 | SNDRV_RAWMIDI_STREAM_OUTPUT = 0, |
| @@ -736,12 +736,38 @@ struct snd_rawmidi_info { · 19 unmodified lines | ||
| 736 | 736 | unsigned char reserved[64]; /* reserved for future use */ |
| 737 | 737 | }; |
| 738 | 738 | |
| 739 | +#define SNDRV_RAWMIDI_MODE_FRAMING_MASK (7<<0) | |
| 740 | +#define SNDRV_RAWMIDI_MODE_FRAMING_SHIFT 0 | |
| 741 | +#define SNDRV_RAWMIDI_MODE_FRAMING_NONE (0<<0) | |
| 742 | +#define SNDRV_RAWMIDI_MODE_FRAMING_TSTAMP (1<<0) | |
| 743 | +#define SNDRV_RAWMIDI_MODE_CLOCK_MASK (7<<3) | |
| 744 | +#define SNDRV_RAWMIDI_MODE_CLOCK_SHIFT 3 | |
| 745 | +#define SNDRV_RAWMIDI_MODE_CLOCK_NONE (0<<3) | |
| 746 | +#define SNDRV_RAWMIDI_MODE_CLOCK_REALTIME (1<<3) | |
| 747 | +#define SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC (2<<3) | |
| 748 | +#define SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC_RAW (3<<3) | |
| 749 | + | |
| 750 | +#define SNDRV_RAWMIDI_FRAMING_DATA_LENGTH 16 | |
| 751 | + | |
| 752 | +struct snd_rawmidi_framing_tstamp { | |
| 753 | + /* For now, frame_type is always 0. Midi 2.0 is expected to add new | |
| 754 | + * types here. Applications are expected to skip unknown frame types. | |
| 755 | + */ | |
| 756 | + __u8 frame_type; | |
| 757 | + __u8 length; /* number of valid bytes in data field */ | |
| 758 | + __u8 reserved[2]; | |
| 759 | + __u32 tv_nsec; /* nanoseconds */ | |
| 760 | + __u64 tv_sec; /* seconds */ | |
| 761 | + __u8 data[SNDRV_RAWMIDI_FRAMING_DATA_LENGTH]; | |
| 762 | +} __packed; | |
| 763 | + | |
| 739 | 764 | struct snd_rawmidi_params { |
| 740 | 765 | int stream; |
| 741 | 766 | size_t buffer_size; /* queue size in bytes */ |
| 742 | 767 | size_t avail_min; /* minimum avail bytes for wakeup */ |
| 743 | 768 | unsigned int no_active_sensing: 1; /* do not send active sensing byte in close() */ |
| 744 | − unsigned char reserved[16]; /* reserved for future use */ | |
| 769 | + unsigned int mode; /* For input data only, frame incoming data */ | |
| 770 | + unsigned char reserved[12]; /* reserved for future use */ | |
| 745 | 771 | }; |
| 746 | 772 | |
| 747 | 773 | #ifndef __KERNEL__ |