SND_SOC_BYTES_EXT was added by commit d98812082c87 ("ASoC: add SND_SOC_BYTES_EXT") to allow drivers to transfer arbitrary byte-aligned data to/from devices via ALSA control interface. Later, SND_SOC_BYTES_TLV was added by commit 7523a271682f ("ASoC: core: add a helper for extended byte controls using TLV") was added for the same purpose and developers expected this to obsolete the former.
However, SND_SOC_BYTES_TLV brought confusions to user land because it doesn't follow to a protocol of ALSA control interface. At least, this macro and related kernel APIs include two misunderstandings: - 'struct snd_ctl_elem_info.count' can also represent the length of TLV packet paylaod, snd_soc_bytes_info_ext() performs in this way. - 'struct snd_ctl_tlv.tlv' can include arbitrary data regardless of TLV packet structure, snd_soc_bytes_tlv_callback() performs in this way.
In a policy of kernel land development, it's quite worse to break protocols for applications. Therefore, developers are discouraged to use these kernel APIs.
In the first place, SND_SOC_BYTES_TLV was added to satisfy a request of developers who need to add control elements which transfer data larger than the size which 'struct snd_ctl_elem_value' can represent; e.g. over 512 bytes. As long as the size is less than the size, SND_SOC_BYTES_EXT is still available. Although there is the limitation of maximum data size, it's better to use this API for stable application interface till better alternative ways are implemented in future.
For these reasons, this commit reverts the previous commit which lead developers to the worse behaviour. Unfortunately, SND_SOC_BYTES_TLV was already merged in development cycle for kernel 3.17 and published, so this commit doesn't touch it for any compatibilities.
Reference: http://mailman.alsa-project.org/pipermail/alsa-devel/2013-November/069483.ht... Reference: commit d98812082c87 ("ASoC: add SND_SOC_BYTES_EXT") Reference: commit 7523a271682f ("ASoC: core: add a helper for extended byte controls using TLV") Cc: Vinod Koul vinod.koul@intel.com Acked-by: Charles Keepax ckeepax@opensource.wolfsonmicro.com Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- include/sound/soc.h | 3 --- 1 file changed, 3 deletions(-)
diff --git a/include/sound/soc.h b/include/sound/soc.h index 6144882..18f7d21 100644 --- a/include/sound/soc.h +++ b/include/sound/soc.h @@ -311,9 +311,6 @@ {.base = xbase, .num_regs = xregs, \ .mask = xmask }) }
-/* - * SND_SOC_BYTES_EXT is deprecated, please USE SND_SOC_BYTES_TLV instead - */ #define SND_SOC_BYTES_EXT(xname, xcount, xhandler_get, xhandler_put) \ { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \ .info = snd_soc_bytes_info_ext, \