From: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
To: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: alsa-devel@alsa-project.org, broonie@linaro.org,
Vinod Koul <vinod.koul@intel.com>,
Clemens Ladisch <clemens@ladisch.de>,
omair.m.abdullah@intel.com, tiwai@suse.de
Subject: Re: [PATCH 1/4] ALSA: control: return payload length for TLV operation
Date: Wed, 31 Aug 2016 10:05:52 +0100 [thread overview]
Message-ID: <20160831090552.GZ21682@localhost.localdomain> (raw)
In-Reply-To: <57C65D4A.9090209@sakamocchi.jp>
On Wed, Aug 31, 2016 at 01:30:02PM +0900, Takashi Sakamoto wrote:
> On Aug 31 2016 13:20, Vinod Koul wrote:
> >> The layout of TLV packet is:
> >> struct snd_ctl_tlv {
> >> unsigned int numid; # numerical ID of a control element
> >> unsigned int length; # length of payload
> >> unsigned int tlv[0]; # payload
> >> };
> >> http://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/tree/include/uapi/sound/asound.h?h=sound-4.8-rc4#n945
> >>
> >> In our implementaion, TLV packet payload (struct snd_ctl_tlv.tlv) is
> >> used to transfer data. For pure threshold level information, we expects
> >> applications and drivers to fill the payload with this protocol:
> >> struct snd_ctl_tlv.tlv[0]: one of SNDRV_CTL_TLVT_XXX
> >> struct snd_ctl_tlv.tlv[1]: length of data
> >> struct snd_ctl_tlv.tlv[2..]: data
> >>
> >> (You can see SNDRV_CTL_TLVT_XXX in this header.
> >> http://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/tree/include/uapi/sound/tlv.h?h=sound-4.8-rc4
> >> )
> >>
> >> On the other hand, ALSA SoC part performs:
> >> struct snd_ctl_tlv.tlv[0..]: arbitrary data
> >>
> >> If your 'tlv[1]' means the 'struct snd_ctl_tlv.tlv[1]', no sense.
> >>
> >> The issue I address is current implementation cannot correctly handle
> >> this case:
> >> - applications request a buffer with a certain size
> >> - drivers processes the request with smaller size
> >> - application cannot get the size
Is this an expected use-case? The TLV controls were implemented
to allow ALSA controls of greater than 512 bytes, I am not sure
the intention was to provide completely generalised binary pipe. In
general the expection for reading a control is that you can
always read the whole control (AFAIK), so it feels like something
returning less than the requested amount of data is buggy.
Thanks,
Charles
next prev parent reply other threads:[~2016-08-31 9:05 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-29 23:44 [RFC][PATCH 0/4] ALSA: control: return payload length of TLV operation Takashi Sakamoto
2016-08-29 23:44 ` [PATCH 1/4] ALSA: control: return payload length for " Takashi Sakamoto
2016-08-30 5:29 ` Takashi Iwai
2016-08-30 6:19 ` Takashi Sakamoto
2016-08-30 6:59 ` Takashi Iwai
2016-08-30 7:13 ` Takashi Sakamoto
2016-08-30 7:39 ` Takashi Iwai
2016-08-30 7:05 ` Clemens Ladisch
2016-08-30 7:09 ` Takashi Sakamoto
2016-08-30 8:04 ` Clemens Ladisch
2016-08-30 12:22 ` Takashi Sakamoto
2016-08-30 14:51 ` Vinod Koul
2016-08-30 22:04 ` Takashi Sakamoto
2016-08-31 4:20 ` Vinod Koul
2016-08-31 4:30 ` Takashi Sakamoto
2016-08-31 9:05 ` Charles Keepax [this message]
2016-08-31 9:40 ` Takashi Iwai
2016-08-31 11:54 ` Clemens Ladisch
2016-08-31 12:08 ` Takashi Iwai
2016-08-31 15:26 ` Takashi Sakamoto
2016-08-31 15:40 ` Takashi Iwai
2016-09-02 11:30 ` Takashi Sakamoto
2016-09-02 13:09 ` Takashi Iwai
2016-09-02 14:50 ` Takashi Sakamoto
2016-09-02 15:19 ` Takashi Iwai
2016-09-02 16:26 ` Takashi Iwai
2016-09-03 11:38 ` Charles Keepax
2016-09-04 11:07 ` Takashi Sakamoto
2016-09-04 20:45 ` Takashi Iwai
2016-09-06 3:30 ` Takashi Sakamoto
2016-09-12 12:37 ` Charles Keepax
2016-09-12 15:25 ` Vinod Koul
2016-09-12 15:28 ` Takashi Iwai
2016-09-12 16:03 ` Charles Keepax
2016-09-12 16:28 ` Takashi Iwai
2016-09-13 8:39 ` Charles Keepax
2016-08-31 12:19 ` Charles Keepax
2016-08-31 13:24 ` Clemens Ladisch
2016-08-31 14:18 ` Charles Keepax
2016-08-31 16:05 ` Vinod Koul
2016-09-02 11:18 ` Takashi Sakamoto
2016-09-02 16:05 ` Takashi Iwai
2016-09-03 3:53 ` Takashi Sakamoto
2016-09-03 11:32 ` Charles Keepax
2016-08-29 23:44 ` [PATCH 2/4] ALSA: control: delegate checking the length of data payload to each drivers Takashi Sakamoto
2016-08-30 15:46 ` Vinod Koul
2016-08-29 23:44 ` [PATCH 3/4] ALSA: control: add kerneldoc for snd_kcontrol_tlv_rw_t Takashi Sakamoto
2016-08-29 23:44 ` [PATCH 4/4] ALSA: control: bump up protocol version to 2.0.8 Takashi Sakamoto
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