From: Takashi Sakamoto Date: Wed, 28 Sep 2016 23:57:24 +0000 (+0900) Subject: ctl: correct documentation about TLV feature X-Git-Tag: v1.1.3~52 X-Git-Url: https://git.alsa-project.org/?a=commitdiff_plain;h=4298736ddad3e61dee2d379c8042f304317a6f3c;p=alsa-lib.git ctl: correct documentation about TLV feature From my misunderstanding, some explanations are wrong. This commit corrects them. Signed-off-by: Takashi Sakamoto Signed-off-by: Takashi Iwai --- 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