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

[Takashi Sakamoto]

On Nov 8 2017 16:05, Takashi Iwai wrote:
> 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.

Now I understand your concern.

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

I'm OK for this suggestion. Later, I'll post updated version of this 
patchset.


Thanks

Takashi Sakamoto