[alsa-devel] [RFC][PATCH 0/3] ALSA: control: delegate TLV eventing to each driver

[Takashi Iwai]

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