From: Jaroslav Kysela <perex@perex.cz>
To: Takashi Iwai <tiwai@suse.de>
Cc: Vinod Koul <vinod.koul@linux.intel.com>,
Mark Brown <broonie@opensource.wolfsonmicro.com>,
alsa <alsa-devel@alsa-project.org>,
Pierre-louis Bossart <pierre-louis.bossart@linux.intel.com>
Subject: Re: data write in alsa
Date: Fri, 02 Dec 2011 08:16:21 +0100 [thread overview]
Message-ID: <4ED87B45.5080603@perex.cz> (raw)
In-Reply-To: <s5hr50no3a9.wl%tiwai@suse.de>
Date 2.12.2011 08:12, Takashi Iwai wrote:
> At Fri, 02 Dec 2011 12:24:41 +0530,
> Vinod Koul wrote:
>>
>> Hi Takashi,
>>
>> For alsa pcm we have two ways to write data, either we use write()
>> system call or use ioctl SNDRV_PCM_IOCTL_WRITEI_FRAMES.
>>
>> Is there any specific reason why we have two methods and which one is
>> preferred and why?
>
> Well, I only remember vaguely. IIRC, ioctl is used since it can pass
> the error code more directly without using errno. Maybe Jaroslav
> knows more exact reason.
The true reason was to avoid the audio frame <-> byte conversions.
> But, honestly speaking, I don't like this implementation. For a new
> interface, I'd suggest to stick with the normal read/write. Otherwise
> you'll get a mess of 32bit compat layer again.
I think that for compressed data, the standard r/w ops are fine, because
there are no "frames".
Jaroslav
--
Jaroslav Kysela <perex@perex.cz>
Linux Kernel Sound Maintainer
ALSA Project; Red Hat, Inc.
next prev parent reply other threads:[~2011-12-02 7:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-02 6:54 data write in alsa Vinod Koul
2011-12-02 7:12 ` Takashi Iwai
2011-12-02 7:16 ` Jaroslav Kysela [this message]
2011-12-02 11:47 ` Vinod Koul
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