On Sun, 27 Mar 2016 14:18:06 +0200, Takashi Sakamoto wrote: > > When audio and music units have some quirks in their sequence of packet, > it's really hard for non-owners to identify the quirks. To handle the > quirks, developers need a dump for sequence of packets at least, however > it's difficult to users who have no knowledge and equipment for this > purpose. > > This commit adds tracepoints for this situation. When users encounter > the issue, they can dump a part of packet data via Linux tracing framework > as long as using drivers in ALSA firewire stack. > > This commit adds 'snd-firewire-lib' subsystem with 'in_packet' and > 'out_packet' events. In the events, the content of CIP headers, the number > of included quadlets and the index of packet managed by this module are > recorded per packet. > > This is a sample: > > $ trace-cmd record -e snd_firewire_lib:out_packet -e snd_firewire_lib:in_packet > /sys/kernel/tracing/events/snd_firewire_lib/out_packet/filter > /sys/kernel/tracing/events/snd_firewire_lib/in_packet/filter > Hit Ctrl^C to stop recording > ^C > $ trace-cmd report trace.dat > ... > <idle>-0 [002] 40398.221702: out_packet: 00070008 9001427a: 058: 31 > <idle>-0 [002] 40398.221703: in_packet: 01020010 9001ffff: 002: 15 > <idle>-0 [002] 40398.221703: out_packet: 00070010 9001ffff: 002: 32 > <idle>-0 [002] 40398.223679: in_packet: 010b0010 900157e4: 090: 16 > <idle>-0 [002] 40398.223681: out_packet: 00070010 900157e4: 058: 33 > <idle>-0 [002] 40398.223681: in_packet: 010b0018 9001714f: 090: 17 > ... > > One line represent one packet. The legend for the last four fields is: > - The first quadlet of CIP header > - The second quadlet of CIP header > - The number of included quadlets > - The index of packet inner buffer maintained by this module > > Currently, when detecting packet discontinuity, this module stops packet > streaming. This is reasonable to packet streaming implementation. However, > to identify the quirks, packet streaming should continue to dump enough > sequence of packet. This commit adds a condition statement and a marker > for this purpose. The packet tracing is nice, and I don't see any reason against it. But changing the driver behavior depending on the trace state is unusual, rather a thing to be avoided in general. thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
