[RFC] compatibility between alsa-kernel and alsa-lib

[RFC] compatibility between alsa-kernel and alsa-lib

[Thierry Vignaud]

Takashi Iwai <tiwai@suse.de> writes:

> > I may have already raised this (sorry), but from times to times, a
> > change in a driver (ie a mixer element change) is coupled with a
> > corresponding change in the config file in
> > /usr/share/alsa/cards/).
> > 
> > This means that there's a point of linkage between alsa-kernel and
> > alsa-lib (that is one has to use older releases for both kernel
> > and libs or new releases for both).
> > 
> > Is there a way to ensure some compatibility, ie alsa-lib-1.0.20
> > will work with both kernel-2.6.32 and kernel-2.6.16 despite driver
> > snd-foobar has changed it's mixer in kernel-2.6.20?
> > 
> > Maybe with versionnated config files or versionnated definitions
> > in the config files?
> > 
> > I know that this can be hard since more and more change will be
> > accumulated (on the other hand, such changes don't happen that
> > often).
> 
> Yes, that's a missing part, so far.
> 
> Currently, we keep the backward compatibility as much as possible.
> For example, if a control element is renamed, we keep the old entry
> with "optional true" attribute so that the same config works for
> older version.  But, this wouldn't work if the device number changes
> or any other critical change occurs.
> 
> The versioned config would be a solution.  The question is how to
> take the version number/string.  One possible idea is that a card
> provides a read-only control element named "Version" with
> IFACE_CARD.  Or simply a new ioctl for this purpose.
> 
> Anyway, this implementation should be more discussed on alsa-devel
> ML.

let's forward it alsa-devel@ ml then.

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Re: [RFC] compatibility between alsa-kernel and alsa-lib

[Thierry Vignaud]

Thierry Vignaud <tvignaud@mandriva.com> writes:

> > Yes, that's a missing part, so far.
> > 
> > Currently, we keep the backward compatibility as much as possible.
> > For example, if a control element is renamed, we keep the old
> > entry with "optional true" attribute so that the same config works
> > for older version.  But, this wouldn't work if the device number
> > changes or any other critical change occurs.
> > 
> > The versioned config would be a solution.  The question is how to
> > take the version number/string.  One possible idea is that a card
> > provides a read-only control element named "Version" with
> > IFACE_CARD.  Or simply a new ioctl for this purpose.
> > 
> > Anyway, this implementation should be more discussed on alsa-devel
> > ML.
> 
> let's forward it alsa-devel@ ml then.

is nobody interested in ensuring compatibility between alsa-lib &
alsa-kernel?
see linus statements about greg wanted to break compatibility with
older udev...

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Re: [RFC] compatibility between alsa-kernel and alsa-lib

[Lee Revell]

On Fri, 2006-08-11 at 17:39 +0200, Thierry Vignaud wrote:
> Thierry Vignaud <tvignaud@mandriva.com> writes:
> 
> > > Yes, that's a missing part, so far.
> > > 
> > > Currently, we keep the backward compatibility as much as possible.
> > > For example, if a control element is renamed, we keep the old
> > > entry with "optional true" attribute so that the same config works
> > > for older version.  But, this wouldn't work if the device number
> > > changes or any other critical change occurs.
> > > 
> > > The versioned config would be a solution.  The question is how to
> > > take the version number/string.  One possible idea is that a card
> > > provides a read-only control element named "Version" with
> > > IFACE_CARD.  Or simply a new ioctl for this purpose.
> > > 
> > > Anyway, this implementation should be more discussed on alsa-devel
> > > ML.
> > 
> > let's forward it alsa-devel@ ml then.
> 
> is nobody interested in ensuring compatibility between alsa-lib &
> alsa-kernel?
> see linus statements about greg wanted to break compatibility with
> older udev...

I thought it was already ALSA policy for a year or so not to make
incompatible changes between alsa-lib and alsa-kernel.

Lee


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Re: [RFC] compatibility between alsa-kernel and alsa-lib

[Takashi Iwai]

At Fri, 11 Aug 2006 11:55:17 -0400,
Lee Revell wrote:
> 
> On Fri, 2006-08-11 at 17:39 +0200, Thierry Vignaud wrote:
> > Thierry Vignaud <tvignaud@mandriva.com> writes:
> > 
> > > > Yes, that's a missing part, so far.
> > > > 
> > > > Currently, we keep the backward compatibility as much as possible.
> > > > For example, if a control element is renamed, we keep the old
> > > > entry with "optional true" attribute so that the same config works
> > > > for older version.  But, this wouldn't work if the device number
> > > > changes or any other critical change occurs.
> > > > 
> > > > The versioned config would be a solution.  The question is how to
> > > > take the version number/string.  One possible idea is that a card
> > > > provides a read-only control element named "Version" with
> > > > IFACE_CARD.  Or simply a new ioctl for this purpose.
> > > > 
> > > > Anyway, this implementation should be more discussed on alsa-devel
> > > > ML.
> > > 
> > > let's forward it alsa-devel@ ml then.
> > 
> > is nobody interested in ensuring compatibility between alsa-lib &
> > alsa-kernel?

Well, at least I'm interested but I've been absent.

> > see linus statements about greg wanted to break compatibility with
> > older udev...
> 
> I thought it was already ALSA policy for a year or so not to make
> incompatible changes between alsa-lib and alsa-kernel.

Right, we do NOT break kernel ABI -- at least, not intentionally.

The problem is the incompatibility of configuration space.
It has been working until now somehow, but there is no good way to
provide a workaround for a bigger change in future.  My suggestion
above is for that purpose.


Takashi

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