Re: [PATCH 5/5] bluetooth.bbclass: set bluez5 as the default BT stack

["Peter A. Bigot" <pab@pabigot.com>]

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On 04/06/2015 04:39 PM, Christopher Larson wrote:
>
> On Mon, Apr 6, 2015 at 2:21 PM, Peter A. Bigot <pab@pabigot.com 
> <mailto:pab@pabigot.com>> wrote:
>
>     On 04/06/2015 09:32 AM, Iorga, Cristian wrote:
>
>         Well,
>
>         1. Peter, Otavio: There is not a single doubt about moving to
>         BlueZ 5 as default in 1.9;
>         2. The requested feedback was about the actual implementation;
>         3. Peter: " I do think it's a bit abrupt to make it the
>         default in the first stable release that provides a usable
>         bluez5."; The change is intended for 1.9,the release that will
>         come in October 2015. Do you think that it is still abrupt?
>         BlueZ5 is present in YP as an alternative BT stack from 1.7,
>         it will still be a fully supported alternative in the
>         (unreleased) 1.8 (as far as upstream goes as "fully
>         supported", of course), it will the default BT stack in 1.9
>         (coming October 2015), while BlueZ 4 will still be supported
>         as an obsolete, but still functional alternative; for 2.0 (why
>         1.10??), if that will be the name, all mechanisms for having
>         BlueZ alternatives will be removed, and BlueZ 5 will be the
>         only official supported BT stack. That's more than two years
>         for a transition, is that too soon??
>
>
>     Sorry; I got confused about which numbers were which and where
>     things are in the release cycle.  I didn't consider bluez5 to be
>     generally usable until the patches that were merged in February
>     for what will be 1.8.  Since both bluez4 and bluez5 will be
>     available in 1.8, making the default bluez5 in 1.9 is fine, and
>     removing bluez4 in what follows is fine.  (I have no idea what
>     version is intended to follow 1.9, but if it isn't some huge
>     backwards-incompatible change I would expect it to be 1.10 rather
>     than 2.0.  That's just from the way I normally manage versioning
>     myself.)
>
>     I have no objections to the technical approach in the patch (it's
>     consistent with what I had in mind when I created that bbclass)
>     but I'm not familiar with how DISTRO_FEATURES_BACKFILL is supposed
>     to work so abstain from further comment.
>
>
> Backfill lets you add features which become default in DISTRO_FEATURES 
> even when a distro overrides DISTRO_FEATURES, unless they explicitly 
> add them to DISTRO_FEATURES_BACKFILL_CONSIDERED.

Thank you.  So, if I understand correctly, the effect of adding bluez5 
to DISTRO_FEATURES_BACKFILL while keeping the current logic:

# bluetooth support on the platform:
# "" if bluetooth is not in DISTRO_FEATURES
# else "bluez5" if bluez5 is in DISTRO_FEATURES
# else "bluez4"

is that bluez5 becomes the default and is in DISTRO_FEATURES 
automatically, and it stays the default even if bluez4 is also in 
DISTRO_FEATURES unless somebody adds bluez5 to 
DISTRO_FEATURES_BACKFILL_CONSIDERED at which point bluez4 takes precedence.

If that understanding is correct, and reviewing 
http://www.yoctoproject.org/docs/latest/ref-manual/ref-manual.html#ref-features-backfill, 
it's not clear to me that it's the right approach.  We're not 
backfilling "bluetooth", which remains optional and continues to control 
whether either "bluez4" or "bluez5" is relevant.  We're changing the 
default provider of bluetooth services, something that I think can 
reasonably be changed between releases, and something that 1.8 already 
controls (via explicit specification of bluez4 or bluez5 in 
DISTRO_FEATURES).

In the absence of more detail on why using DISTRO_FEATURES_BACKFILL is a 
better solution I prefer Cristian's original approach.

Peter


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