On Mon, 11 Nov 2019 12:08:39 +0100, Andrew Gabbasov wrote: > > This patch set is an updated version of patches by Timo Wischer: > https://mailman.alsa-project.org/pipermail/alsa-devel/2019-March/146871.html > > This patch set is required for forwarding audio data between a HW sound > card and an aloop device without the usage of an asynchronous sample rate > converter. > > Most of sound and timers related code is kept the same as in previous set. > The code, related to snd_pcm_link() functionality and its using for > timer source setting, is removed (as rejected earlier). The changes in this > update are mainly related to the parameters handling and some cleanup. > > The timer source can be initially selected by "timer_source" kernel module > parameter. It is supposed to have the following format: > [<pref>:](<card name>|<card idx>)[{.,}<dev idx>[{.,}<subdev idx>]] > For example: "hw:I82801AAICH.1.0", or "1.1", or just "I82801AAICH". > (Prefix is ignored, just allowed here to be able to use the strings, > the user got used to). > Although the parsing function recognizes both '.' and ',' as a separator, > module parameters handling routines use ',' to separate parameters for > different module instances (array elements), so we have to use '.' > to separate device and subdevice numbers from the card name or number > in module parameters. > Empty string indicates using jiffies as a timer source. > > Besides "static" selection of timer source at module load time, > it is possible to dynamically change it via sound "info" interface > (using "/proc/asound/<card>/timer_source" file in read-write mode. > The contents of this file is used as a timer source string for > a particular loopback card, e.g. "hw:0,0,0" (and here ',' can be used > as a separator). > > The timer source string value can be changed at any time, but it is > latched by PCM substream open callback "loopback_open()" (the first > one for a particular cable). At this point it is actually used, > that is the string is parsed, and the timer is looked up and opened. > This seems to be a good trade-off between flexibility of updates and > synchronizations or racing complexity. > > The timer source is set for a loopback card (the same as initial setting > by module parameter), but every cable uses the value, current at the moment > of opening. Theoretically, it's possible to set the timer source for each > cable independently (via separate files), but it would be inconsistent > with the initial setting via module parameters on a per-card basis. > > v2: > https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/157961.html > > v3: > - Change sound card lookup to use snd_card_ref() and avoid direct access > to sound cards array > - Squash commits on returning error codes for timer start and stop > - Some locking related fixes > - Some code cleanup The patch won't work with the latest ALSA timer code found in my for-next branch due to the API changes. Essentially you need to rewrite as: timeri = snd_timer_instance_new(...); if (!timeri) no_memory_error; timeri->flags |= ...; timeri->ccallback = ...; .... err = snd_timer_open(timeri, ....); if (err < 0) error; thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
