On Jun 12 2016 17:31, Henrik Austad wrote: > On Sun, Jun 12, 2016 at 01:30:24PM +0900, Takashi Sakamoto wrote: >> On Jun 12 2016 12:38, Takashi Sakamoto wrote: >>> In your patcset, there's no actual codes about how to handle any >>> interrupt contexts (software / hardware), how to handle packet payload, >>> and so on. Especially, for recent sound subsystem, the timing of >>> generating interrupts and which context does what works are important to >>> reduce playback/capture latency and power consumption. >>> >>> Of source, your intention of this patchset is to show your early concept >>> of TSN feature. Nevertheless, both of explaination and codes are >>> important to the other developers who have little knowledges about TSN, >>> AVB and AES-64 such as me. >> >> Oops. Your 5th patch was skipped by alsa-project.org. I guess that size >> of the patch is too large to the list service. I can see it: >> http://marc.info/?l=linux-netdev&m=146568672728661&w=2 >> >> As long as seeing the patch, packets are queueing in hrtimer callbacks >> every 1 seconds. > > Actually, the hrtimer fires every 1ms, and that part is something I have to > do something about, also because it sends of the same number of frames > every time, regardless of how accurate the internal timer is to the rest of > the network (there's no backpressure from the networking layer). > >> (This is a high level discussion and it's OK to ignore it for the >> moment. When writing packet-oriented drivers for sound subsystem, you >> need to pay special attention to accuracy of the number of PCM frames >> transferred currently, and granularity of the number of PCM frames >> transferred by one operation. In this case, snd_avb_hw, >> snd_avb_pcm_pointer(), tsn_buffer_write_net() and tsn_buffer_read_net() >> are involved in this discussion. You can see ALSA developers' struggle >> in USB audio device class drivers and (of cource) IEC 61883-1/6 drivers.) > > Ah, good point. Any particular parts of the USB-subsystem I should start > looking at? I don't think it's a beter way for you to study USB Audio Device Class driver unless you're interested in ALSA or USB subsystem. (But for your information, snd-usb-audio is in sound/usb/* of Linux kernel. IEC 61883-1/6 driver is in sound/firewire/*.) We need different strategy to achieve it on different transmission backend. > Knowing where to start looking is a tremendous help It's not well-documented, and not well-generalized for packet-oriented drivers. Most of developers who have enough knowledge about it work for DMA-oriented drivers in mobile platforms and have little interests in packet-oriented drivers. You need to find your own way. Currently I have few advices to you, because I'm also on the way for drivers to process IEC 61883-1/6 packets on IEEE 1394 bus with enough accuracy and granularity. The paper I introduced is for the way (but not mature). I wish you get more helps from the other developers. Your work is more significant to Linux system, than mine. (And I hope your future work get no ignorance and no unreasonable hostility from coarse users.) Regards Takashi Sakamoto
Attachment:
signature.asc
Description: OpenPGP digital signature
_______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
