Hello Takashi, > -----Original Message----- > From: Takashi Iwai [mailto:tiwai@xxxxxxx] > Sent: Thursday, November 14, 2019 8:11 PM > To: Gabbasov, Andrew > Cc: alsa-devel@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Jaroslav > Kysela; Takashi Iwai; Timo Wischer > Subject: Re: [PATCH v3 0/7] ALSA: aloop: Support sound timer as clock > source instead of jiffies > > 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; > The updated patch set version 4 was sent to mailing list: https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/158896.h tml It is based on the linux-next repo master branch as of Nov 19, 2019. Thanks! Best regards, Andrew _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
