From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre-Louis Bossart Subject: Re: [PATCH RFC 5/9] ALSA: core: selection of audio_tstamp type and accuracy reports Date: Wed, 10 Dec 2014 11:27:26 -0600 Message-ID: <5488827E.4030403@linux.intel.com> References: <1418077426-8309-1-git-send-email-pierre-louis.bossart@linux.intel.com> <1418077426-8309-6-git-send-email-pierre-louis.bossart@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by alsa0.perex.cz (Postfix) with ESMTP id 9EB14260594 for ; Wed, 10 Dec 2014 18:32:32 +0100 (CET) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Takashi Iwai Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On 12/10/14, 10:35 AM, Takashi Iwai wrote: > Just a minor issue before going to detailed review: > > At Mon, 8 Dec 2014 16:23:42 -0600, > Pierre-Louis Bossart wrote: >> >> +/* user space provides config to kernel */ >> +struct snd_pcm_audio_tstamp_config { >> + __u32 type_requested:4; >> + __u32 report_delay:1; /* add total delay to A/D or D/A */ >> +}; > .... >> +/* kernel provides report to user-space */ >> +struct snd_pcm_audio_tstamp_report { >> + /* actual type if hardware could not support requested timestamp */ >> + __u32 actual_type:4; >> + >> + /* accuracy represented in mantissa/exponent form */ >> + __u32 accuracy_report:1; /* 0 if accuracy unknown, 1 if rest of structure is valid */ >> + __u32 accuracy_m:7; /* 0..127, ~3 significant digit for mantissa */ >> + __u32 accuracy_e:4; /* base10 exponent, 0 for ns, 3 for us, 6 for ms, 9 for s */ >> +}; > > Please avoid the bit fields in these, since these values will be a > part of ABI. There is absolutely no compatibility when you're using > bitfields. Use the explicit bit operations. Those definitions are not used as part of the kernel/user interaction, I did use pack/unpack operations as requested in previous reviews. see snd_pcm_unpack_tstamp_config and snd_pcm_pack_audio_tstamp_report. A similar pack/unpack operation is provided in the alsa-lib patches The data is exchanged using the reclaimed 32-bit word only. Would that work? > > thanks, > > Takashi > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel >