[alsa-devel] [alsa-lib][PATCH 1/2] ctl: deprecate APIs of dimension information

[Takashi Iwai]

On Tue, 07 Nov 2017 23:36:28 +0100,
Takashi Sakamoto wrote:
> 
> On Nov 7 2017 16:59, Takashi Iwai wrote:
> > On Tue, 07 Nov 2017 01:34:02 +0100,
> > Takashi Sakamoto wrote:
> >>
> >>>> This commit deprecates some APIs related to the dimension information. They
> >>>> are planned to be removed in a development period for Linux kernel v4.21.
> >>>
> >>> IMO, the version to deprecate the feature may depend on LTS kernel
> >>> version.  4.21 looks OK, but we may shift it.
> >>
> >> I still get no merit of your suggestion. Do you mean that the removal
> >> of ABI should be done in several releases before target LTS will be
> >> actually released, to produce stable ABI? If so, we need to estimate
> >> the timing of next LTS. However, it's hard because for recent LTS we
> >> got no official announcement from stable maintainers till LTS version
> >> of Linux kernel is actually released. At least, I won't work with such
> >> uncertain estimations.
> >
> > The feature removal isn't what we can guarantee at a certain kernel
> > version.  As long as we have a real (not theoretical) user, it
> > shouldn't be dropped.  It's still unwritten "no regression" rule.
> >
> > That said, we may announce and prepare / plan the deprecation, but we
> > can't define the exact kernel version in general.  And considering LTS
> > release is one of the decision factors.
> 
> If it comes from a general theory, I'm willing to follow it.
> 
> But in this case, we can be optimistic. As you know, the minor feature
> is just used in drivers/software related to models produced by Echo
> Digital Audio corp. The other probability is usage by user-defined
> control element set on any userspace application. As my recent work
> declared, this feature has been long-abandoned and no application
> exists (if such application exists, developers have already found such
> bugs which I've fixed recently before I worked...).
> 
> If the feature were used by majority, it would be more difficult to
> deprecate/remove it, and we need to be deliberate. Depending on cases,
> deprecation is impossible itself. But this feature is quite minor and
> got little popularity. Practically, we can safely remove the minor
> feature in any timing after modified version of echoaudio stuffs are
> disseminated. My proposed schedule takes 6 kernel releases for it. In
> the schedule, v4.21 release is the deadline of the feature, but if
> you'd like to keep the deadline undecided for such theory/rule, I have
> no objection to it. To me, deprecation of this feature for future
> removal is more important to avoid developers' misuses to which I
> addressed, than actual removal.

I have no objection of removal of API in alsa-lib, but my concern is
that unnecessary announcement of the exact kernel version as if it's
an ultimately fixed deadline.  It's rather a "hopefully working"
deadline, and we don't need to show it in alsa-lib side.

We can update the comment once after it's really deprecated, if any.


thanks,

Takashi