From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D874FC282CD for ; Mon, 28 Jan 2019 23:48:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A44F7217F5 for ; Mon, 28 Jan 2019 23:48:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548719333; bh=T1JDq569bCa0/O5mBZjLGYp4h1D1NWq0r8sxhNDCcMA=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=pvsI/pXQQ+RuRELngInie6nqSOoIIUrLQXO64AtlcDDhZaXYPPf6TZywZVixxlgS1 dduemVoIfN0YFNf+VveW6R7na9NW1CjpgmBH7XBe0L5cwJK34PsUPKmUmjGmcxIVxP TcZvNdC1DDWbkHzEKK91TuYd9TFEUN2GeP6frPVg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727623AbfA1Xsw (ORCPT ); Mon, 28 Jan 2019 18:48:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:40420 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726937AbfA1Xsv (ORCPT ); Mon, 28 Jan 2019 18:48:51 -0500 Received: from [192.168.1.112] (c-24-9-64-241.hsd1.co.comcast.net [24.9.64.241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 510172171F; Mon, 28 Jan 2019 23:48:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548719330; bh=T1JDq569bCa0/O5mBZjLGYp4h1D1NWq0r8sxhNDCcMA=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=fXscI4SdJeERU8D6a9kuQE3hwveJK+EAuVzcTPjiEK9QLxHlmGBOJI5y4hhLK/MRQ U7ZZydhToGojnem53lL8YrTJSOsYkIsHPQfJGvwFmGQtYtZ05ol/wF3ql9RqRQbmUs uxl/TAicsLSlbvnmGyjO2bcnSxjQxBcoxddAJGK4= Subject: Re: [PATCH v10 0/4] Media Device Allocator API To: Hans Verkuil , mchehab@kernel.org, perex@perex.cz, tiwai@suse.com Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org, shuah References: From: shuah Message-ID: <481787e7-112a-80dd-228c-2497a12547b9@kernel.org> Date: Mon, 28 Jan 2019 16:48:49 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Hans, On 1/28/19 5:03 AM, Hans Verkuil wrote: > Hi Shuah, > > On 1/24/19 9:32 PM, Shuah Khan wrote: >> Media Device Allocator API to allows multiple drivers share a media device. >> This API solves a very common use-case for media devices where one physical >> device (an USB stick) provides both audio and video. When such media device >> exposes a standard USB Audio class, a proprietary Video class, two or more >> independent drivers will share a single physical USB bridge. In such cases, >> it is necessary to coordinate access to the shared resource. >> >> Using this API, drivers can allocate a media device with the shared struct >> device as the key. Once the media device is allocated by a driver, other >> drivers can get a reference to it. The media device is released when all >> the references are released. >> >> - This patch series is tested on 5.0-rc3 and addresses comments on >> v9 series from Hans Verkuil. >> - v9 was tested on 4.20-rc6. >> - Tested sharing resources with kaffeine, vlc, xawtv, tvtime, and >> arecord. When analog is streaming, digital and audio user-space >> applications detect that the tuner is busy and exit. When digital >> is streaming, analog and audio applications detect that the tuner is >> busy and exit. When arecord is owns the tuner, digital and analog >> detect that the tuner is busy and exit. > > I've been doing some testing with my au0828, and I am confused about one > thing, probably because it has been too long ago since I last looked into > this in detail: > Great. > Why can't I change the tuner frequency if arecord (and only arecord) is > streaming audio? If arecord is streaming, then it is recording the audio > from the analog TV tuner, right? So changing the analog TV frequency > should be fine. > Changing analog TV frequency would be s_frequency. The way it works is any s_* calls would require holding the pipeline. In Analog TV case, it would mean holding both audio and video pipelines for any changes including TV. As I recall, we discussed this design and the decision was to make all s_* calls interfaces to hold the tuner. A special exception is g_tuner in case of au0828. au0828 initializes the tuner from s_* interfaces and its g_tuner interfaces. Allowing s_frequency to proceed will disrupt the arecord audio stream. Query (q_*) works just fine without holding the pipeline. I limited the analog holds to just the ones that are required. The current set is required to avoid audio stream disruptions. I made sure v4l-ctl --all works when the pipeline is locked by any one of the 3 (audio, video, DVB). Hope this helps. thanks, -- Shuah