From gd78059@sac.sfbay.sun.com Mon Nov 23 11:13:29 2009 Received: from sunmail6brm.central.sun.com (sunmail6brm.Central.Sun.COM [129.147.4.169]) by sac.sfbay.sun.com (8.13.8+Sun/8.13.8) with ESMTP id nANJDTuR008990 for ; Mon, 23 Nov 2009 11:13:29 -0800 (PST) Received: from nwk-avmta-2.sfbay.sun.com (nwk-avmta-2.SFBay.Sun.COM [129.145.155.6]) by sunmail6brm.central.sun.com (8.13.8+Sun/8.13.8/ENSMAIL,v2.4) with ESMTP id nANJDSvY025172; Mon, 23 Nov 2009 13:13:29 -0600 (CST) Received: from pmxchannel-daemon.nwk-avmta-2.sfbay.sun.com by nwk-avmta-2.sfbay.sun.com (Sun Java System Messaging Server 6.2-3.04 (built Jul 15 2005)) id <0KTK00J0VTEGEO00@nwk-avmta-2.sfbay.sun.com>; Mon, 23 Nov 2009 11:13:28 -0800 (PST) Received: from dm-sfbay-02.sfbay.sun.com ([129.146.11.31]) by nwk-avmta-2.sfbay.sun.com (Sun Java System Messaging Server 6.2-3.04 (built Jul 15 2005)) with ESMTP id <0KTK008GETEFCBD0@nwk-avmta-2.sfbay.sun.com>; Mon, 23 Nov 2009 11:13:27 -0800 (PST) Received: from sac.sfbay.sun.com (sac.SFBay.Sun.COM [129.146.226.132]) by dm-sfbay-02.sfbay.sun.com (8.13.8+Sun/8.13.8/ENSMAIL,v2.4) with ESMTP id nANJDRWj005336; Mon, 23 Nov 2009 11:13:27 -0800 (PST) Received: from sac.sfbay.sun.com (localhost [127.0.0.1]) by sac.sfbay.sun.com (8.13.8+Sun/8.13.8) with ESMTP id nANJDQiq008969; Mon, 23 Nov 2009 11:13:26 -0800 (PST) Received: (from gd78059@localhost) by sac.sfbay.sun.com (8.13.8+Sun/8.13.8/Submit) id nANJDQ5t008957; Mon, 23 Nov 2009 11:13:26 -0800 (PST) Date: Mon, 23 Nov 2009 11:13:26 -0800 (PST) From: "Garrett D'Amore - sun microsystems" Subject: audio_engine_playahead/qlen [PSARC/2009/639 Self Review] To: PSARC-ext@sun.com Cc: audio-oss-ext@sun.com Message-id: <200911231913.nANJDQ5t008957@sac.sfbay.sun.com> Content-transfer-encoding: 7BIT X-PMX-Version: 5.4.1.325704 Status: RO Content-Length: 3938 The following case documents an intent to make a couple of minor bug-fix related changes to the Boomer audio driver DDI. As the changes affect only a consolidation private API which has not been released in any official product yet, both the consumers and producers of the interfaces are owned by the same project team, and the changes themselves are very minor "obvious" changes to the interface, we believe self-review is appropriate. This case is for Minor binding, and retains the Consolidation Private commitment level for the Boomer DDI. (Note that at some future point we anticipate making some further, and perhaps significant, changes to this portion of the Boomer DDI. The details of any such changes are still under investigation, however.) Template Version: @(#)sac_nextcase 1.68 02/23/09 SMI This information is Copyright 2009 Sun Microsystems 1. Introduction 1.1. Project/Component Working Name: audio_engine_playahead/qlen 1.2. Name of Document Author/Supplier: Author: Garrett D'Amore 1.3 Date of This Document: 23 November, 2009 4. Technical Description Problem: Debugging CR 6901849 (audio810 is choppy when run in a virtualbox guest), it turns out that we need to queue up more audio data than we would need to for a "real device". We're going to have this requirement for Sun Ray audio as well. Boomer (PSARC 2008/318) currently queues up 1.5 "fragments" (interrupt periods) worth of data by default. We need to provide a way for drivers to ask for more data to be queued to them, without changing the interrupt frequency for the device. While here, we found two issues with the audio_engine_qlen() entry point: 1) It returns a size_t, inconsistently with respect to other entry points which use unsigned for small frame counts. 2) It is "mandatory", but nearly all device drivers have entry points which simply return 0. It seems like we could make this entry point optional and save a few lines of code in many of the device drivers. (Only drivers with deep FIFOs, or without an ability to accurately report position data, need this. Right now that means only audiocs and usb_ac. In the future it will include Sun Ray audio, and we can probably eliminate it for usb_ac with some enhancements to that code.) Solution: A) We provide a new entry point in audio_engine_ops, audio_engine_playahead. It simply returns a count in frames of data that should be queued for the device. The prototype is: unsigned audio_engine_playahead(void *); This entry point is added to the end of the audio_engine_ops structure. NULL may be supplied to use the default value. Note that the default of 1.5 fragments is used if an unreasonable value is returned. (Reasonable values are more than 1.5 fragments, and not more than the total audio buffer size.) B) We have changed the prototype for audio_engine_qlen() as follows: unsigned audio_engine_qlen(void *); NULL may be supplied, in which case the hardware FIFO depth is assumed to be zero. Note that for very small hardware FIFOs, such as 64 frames, it is still reasonable to supply NULL. (The difference amounts to less than 2 milliseconds of error in latency reporting.) C) To accomodate the above change, the audio_engine_version member of the audio_engine_ops structure is bumped from 0 to 1. This should prevent any errorneous attempt to use a driver built against an older (or newer) header from operating with the revised framework. Note that since this is a consolidation private API, we are not doing anything more than simply refusing to register an engine with an invalid version. (There is no need to support using older drivers with the updated framework.) 6. Resources and Schedule 6.4. Steering Committee requested information 6.4.1. Consolidation C-team Name: ON 6.5. ARC review type: Automatic 6.6. ARC Exposure: open