On Tue, 22 Aug 2017 01:42:19 +0200, Takashi Sakamoto wrote:
Hi,
This patchset is to avoid a trouble on ALSA control core, kernel API of ALSA control component and ALSA control interface/protocol to handle TLV operations from user space.
In a design of ALSA control core, a set of elements is represented by 'struct snd_kcontrol' to share common attributes. The set of elements shares TLV (Type-Length-Value) data, too.
On the other hand, in ALSA control interface/protocol for applications, a TLV operation is committed to an element. Totally, the operation can have sub-effect to the other elements in the set. For example, TLV_WRITE operation is expected to change TLV data, which returns to applications. Applications attempt to change the TLV data per element, but in the above design, they can effect to elements in the same set.
As a default, ALSA control core has no implementation except for TLV_READ operation. Thus, the above design looks to have no issue. However, in kernel APIs of ALSA control component, developers can program a handler for any request of the TLV operation. Therefore, for elements in a set which has the handler, applications can commit TLV_WRITE and TLV_COMMAND requests.
For the above scenario, ALSA control core assist notification. When the handler returns positive value, the core queueing an event for a requested element. However, this includes design defects that the event is not queued for the other element in a set. Actually, developers can program the handlers to keep per-element TLV data, but it depends on each driver.
In this patchset, I attempts to solve the above issue, by delegating the event notification to each driver of ALSA control component.
Additionally, this patchset includes a solution against an issue in below message thread:
[alsa-devel] snd_ctl_add_enumerated_elem_set and TLV http://mailman.alsa-project.org/pipermail/alsa-devel/2017-July/123364.html
Takashi Sakamoto (3): ALSA: control: delegate TLV eventing to each driver ALSA: control: queue TLV event for all of elements in an user-defined set ALSA: control: disable TLV data at initial state of user-defined element set
The patch set looks OK to me through a quick glance. If it's confirmed to work with your tests, feel free to resubmit as the patches for merge.
thanks,
Takashi