Takashi Iwai
4f7fd72c0e
- Backport upstream fixes: 0001-ucm-substitution-remove-duplicate-allow_empty-assign.patch 0002-ucm-fix-parse_get_safe_name-safe-name-must-be-checke.patch 0003-ucm-substitute-the-merged-tree-completely.patch 0004-ctl-improve-documentation-for-identifier-of-control-.patch 0005-pcm-dmix-make-lockless-operation-optional.patch 0006-pcm-dmix-Fix-semaphore-usage-with-lockless-operation.patch 0007-pcm-iec958-implement-HDMI-HBR-audio-formatting.patch 0008-pcm-iec958-set-channel-status-bits-according-to-rate.patch 0009-conf-pcm-USB-Added-S-PDIF-fix-for-Asus-Xonar-SE.patch 0010-control-ctlparse-fix-enum-values-in-or.patch 0011-conf-USB-Audio-Disable-IEC958-on-Lenovo-ThinkStation.patch 0012-pcm-dmix-fix-access-to-sum-buffer-in-non-interleaved.patch 0014-control-Add-documentation-for-snd_ctl_elem_list_.patch 0015-conf-quote-also-strings-with-and-characters-in-strin.patch 0016-topology-decode-Fix-channel-map-memory-allocation.patch 0017-topology-decode-Fix-infinite-loop-in-decoding-enum-c.patch 0018-topology-decode-Remove-decoding-values-for-enum-cont.patch 0019-topology-decode-Add-enum-control-texts-as-separate-e.patch 0020-topology-decode-Fix-printing-texts-section.patch 0021-topology-decode-Change-declaration-of-enum-decoding-.patch 0022-topology-decode-Fix-decoding-PCM-formats-and-rates.patch 0023-topology-decode-Print-sig_bits-field-in-PCM-capabili.patch 0024-topology-decode-Add-DAI-name-printing.patch 0025-topology-Make-buffer-for-saving-dynamic-size.patch 0026-topology-return-correct-value-in-tplg_save_printf.patch 0027-topology-fix-some-gcc10-warnings-labs-signess.patch 0028-topology-fix-sort_config.patch 0029-topology-fix-the-unaligned-access.patch 0030-topology-improve-the-printf-buffer-management.patch OBS-URL: https://build.opensuse.org/request/show/836375 OBS-URL: https://build.opensuse.org/package/show/multimedia:libs/alsa?expand=0&rev=281
112 lines
4.5 KiB
Diff
112 lines
4.5 KiB
Diff
From 84185b5c94ec8a214103b8ec02d272f0158c24e6 Mon Sep 17 00:00:00 2001
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From: "Tanjeff-N. Moos" <tanjeff@cccmz.de>
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Date: Wed, 2 Sep 2020 11:27:26 +0200
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Subject: [PATCH 31/32] control: Improve general control interface
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documentation.
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Signed-off-by: Tanjeff-N. Moos <tanjeff@cccmz.de>
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Signed-off-by: Takashi Iwai <tiwai@suse.de>
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---
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src/control/control.c | 72 ++++++++++++++++++++++++++++++++++++++++++++-------
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1 file changed, 63 insertions(+), 9 deletions(-)
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diff --git a/src/control/control.c b/src/control/control.c
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index 1bcf1ab2e431..497a5399b7e6 100644
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--- a/src/control/control.c
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+++ b/src/control/control.c
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@@ -31,7 +31,7 @@
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/*! \page control Control interface
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<P>Control interface is designed to access primitive controls. There is
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-also interface notifying about control and structure changes.
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+also an interface for notifying about control and structure changes.
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\section control_general_overview General overview
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@@ -43,20 +43,74 @@ are managed according to below model.
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Some element sets can be added to a sound card by drivers in kernel and
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userspace applications.
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- element
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- - An element can be identified by userspace applications. Each element has
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- own identical information.
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+ - A control element might be a master volume control, for example, or a
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+ read-only indicator, such as a sync status. An element has a type (e.g.
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+ INTEGER or BOOLEAN) and - depending on the type - min/max values, a step
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+ size, a set of possible values (for enums), etc.
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- member
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- - An element includes some members to have a value. The value of each member
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- can be changed by both of userspace applications and drivers in kernel.
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-Each element can be identified by two ways; the numerical number (numid), or the
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-combination of interface, device, subdevice, name, and index.
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+ - An element includes one or more member(s) to have a value. For
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+ example, a stereo volume control element has two members (for
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+ left/right). The members share the same properties (e.g. both
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+ volume controls have the same min/max values). The value of each
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+ member can be changed by both of userspace applications and
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+ drivers in kernel.
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-The type of element set is one of integer, integerr64, boolean, enumerators,
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+
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+\section identifying_elements Identifying the Elements
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+
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+Each element has the following identifying properties:
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+
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+ - The numid (a numeric identifier, assigned when the sound card is
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+ detected, constant while the sound card is kept connected)
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+
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+ - The interface type (e.g. MIXER, CARD or PCM)
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+ - The device
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+ - The subdevice
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+ - Its name
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+ - Its index
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+
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+An element can be identified either by its numid or by the tuple
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+(interface type, device, subdevice, name, index). This tuple is always
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+the same (driver updates can change it, but in practice this is
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+rare). The numid can change on each boot. In case of an USB sound
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+card, the numid can also change when it is reconnected.
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+
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+
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+\section element_lists Element Lists
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+
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+An element list can be used to obtain a list of all elements of the
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+sound card. The list contains generic information (e.g. how many
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+elements the card has), and the identifying properties of the elements
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+(numid, card, name, ...). See #snd_ctl_elem_list_t to learn more about
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+element lists.
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+
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+
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+\section working_with_elements Working with Elements
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+
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+It is possible to obtain information about an element using the
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+snd_ctl_elem_info_*() functions. For enums, the allowed values can be
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+obtained, for integers, the min/max values can be obtained, and so
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+on. In addition, these functions can report the identifying
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+properties. E.g. when the element is addressed using its numid, the
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+functions complements the name, index, etc.
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+
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+To access the values of a control, use the snd_ctl_elem_value*()
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+functions. These allow to get and set the actual values or
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+settings. It is also possible to get and set the ID values (such as
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+the numid or the name).
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+
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+
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+\section element_sets Element Sets
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+
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+The type of element set is one of integer, integer64, boolean, enumerators,
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bytes and IEC958 structure. This indicates the type of value for each member in
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elements included in the element set.
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-When the value of member is changed, corresponding events are transferred to
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+
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+\section events Events
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+
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+When the value of a member is changed, corresponding events are transferred to
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userspace applications. The applications should subscribe any events in advance.
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\section tlv_blob Supplemental data for elements in an element set
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--
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2.16.4
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