1. May 28, 2021
    • Takashi Sakamoto's avatar
      ALSA: firewire-lib: add replay target to cache sequence of packet · f9e5ecdf
      Takashi Sakamoto authored
      
      
      In design of audio and music unit in IEEE 1394 bus, feedback of
      effective sampling transfer frequency (STF) is delivered by packets
      transferred from device. The devices supported by ALSA firewire stack
      are categorized to three groups regarding to it.
      
       * Group 1:
         * Echo Audio Fireworks board module
         * Oxford Semiconductor OXFW971 ASIC
         * Digidesign Digi00x family
         * Tascam FireWire series
         * RME Fireface series
      
       * Group 2:
         * BridgeCo. DM1000/DM1100/DM1500 ASICs for BeBoB solution
         * TC Applied Technologies DICE ASICs
      
       * Group 3:
         * Mark of the Unicord FireWire series
      
      In group 1, the effective STF is determined by the sequence of the number
      of events per packet. In group 2, the sequence of presentation timestamp
      expressed in syt field of CIP header is interpreted as well. In group 3,
      the presentation timestamp is expressed in source packet header (SPH) of
      each data block.
      
      I note that some models doesn't take care of effective STF with large
      internal buffer. It's reasonable to name it as group 0:
      
       * Group 0
         * Oxford Semiconductor OXFW970 ASIC
      
      The effective STF is known to be slightly different from nominal STF for
      all of devices, and to be different between the devices. Furthermore, the
      effective STF is known to be shifted for long-period transmission. This
      makes it hard for software to satisfy the effective STF when processing
      packets to the device.
      
      The effective STF is deterministic as a result of analyzing the batch of
      packet transferred from the device. For the analysis, caching the sequence
      of parameter in the packet is required.
      
      This commit adds an option so that AMDTP domain structure takes AMDTP
      stream structure to cache the sequence of parameters in packet transferred
      from the device. The parameters are offset ticks of syt field against the
      cycle to receive the packet and the number of data blocks per packet.
      
      Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
      Link: https://lore.kernel.org/r/20210527122611.173711-2-o-takashi@sakamocchi.jp
      
      
      Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      f9e5ecdf
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