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author | Takashi Sakamoto <o-takashi@sakamocchi.jp> | 2016-09-29 08:57:24 +0900 |
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committer | Takashi Iwai <tiwai@suse.de> | 2016-09-30 17:13:11 +0200 |
commit | 4298736ddad3e61dee2d379c8042f304317a6f3c (patch) | |
tree | f7d85192f4d8a7af42920601308d3abdcc408df8 /src/control/control.c | |
parent | e55d735f84364d3b7d38104cee37c968e3797ea4 (diff) | |
download | alsa-lib-4298736ddad3e61dee2d379c8042f304317a6f3c.tar.gz |
ctl: correct documentation about TLV feature
From my misunderstanding, some explanations are wrong. This commit
corrects them.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'src/control/control.c')
-rw-r--r-- | src/control/control.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/src/control/control.c b/src/control/control.c index 40ee9b75..134ba4c8 100644 --- a/src/control/control.c +++ b/src/control/control.c @@ -59,27 +59,27 @@ elements included in the element set. When the value of member is changed, corresponding events are transferred to userspace applications. The applications should subscribe any events in advance. -\section tlv_blob Thredshold level and arbitrary data +\section tlv_blob Supplemental data for elements in an element set -TLV feature is designed to transfer data about threshold level between a driver -and any userspace applications. The data is for an element set. +TLV feature is designed to transfer data in a shape of Type/Length/Value, +between a driver and any userspace applications. The main purpose is to attach +supplement information for elements to an element set; e.g. dB range. At first, this feature was implemented to add pre-defined data readable to userspace applications. Soon, it was extended to handle several operations; read, write and command. The original implementation remains as the read operation. The command operation allows drivers to have own implementations -against requests from userspace applications. As of 2016, simple write operation -is not supported yet. +against requests from userspace applications. This feature was introduced to ALSA control feature in 2006, at commit c7a0708a2362, corresponding to a series of work for Linux kernel (42750b04c5ba and 8aa9b586e420). -This feature can transfer arbitrary data in a shape of an array with members of -unsigned int type, therefore it can be used to deliver quite large arbitrary -data from userspace to in-kernel drivers via ALSA control character device. -Focusing on this nature, some in-kernel implementations utilize this feature for -I/O operations. +There's no limitation about maximum size of the data, therefore it can be used +to deliver quite large arbitrary data from userspace to in-kernel drivers via +ALSA control character device. Focusing on this nature, as of 2016, some +in-kernel implementations utilize this feature for I/O operations. This is +against the original design. */ #include <stdio.h> |