[yocto] [meta-raspberrypi][PATCH 1/3] raspberrypi2.conf: Make SERIAL_CONSOLE overwritable

[Paul Barker]

On Fri, Apr 21, 2017 at 5:03 PM, Andrei Gherzan <andrei at gherzan.ro> wrote:
> On Thu, Apr 20, 2017 at 06:18:14PM +0100, Andrei Gherzan wrote:
>> Signed-off-by: Andrei Gherzan <andrei at gherzan.ro>
>> ---
>>  conf/machine/raspberrypi2.conf | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/conf/machine/raspberrypi2.conf b/conf/machine/raspberrypi2.conf
>> index 9b4c02a..a17289c 100644
>> --- a/conf/machine/raspberrypi2.conf
>> +++ b/conf/machine/raspberrypi2.conf
>> @@ -7,7 +7,7 @@ DEFAULTTUNE ?= "cortexa7thf-neon-vfpv4"
>>  require conf/machine/include/tune-cortexa7.inc
>>  include conf/machine/include/rpi-base.inc
>>
>> -SERIAL_CONSOLE = "115200 ttyAMA0"
>> +SERIAL_CONSOLE ?= "115200 ttyAMA0"
>>
>>  UBOOT_MACHINE = "rpi_2_config"
>>  VC4_CMA_SIZE ?= "cma-256"
>> --
>> 2.12.2
>>
>
> Entire patch set merged to master and morty.
>

This is the sort of thing I'm not keen on applying to stable branches
as it may change recipe behaviour. For comparison, the stable branch
policy for oe-core is very strict
(https://wiki.yoctoproject.org/wiki/Stable_branch_maintenance#Policies).

In my mind, avoiding potential breakage on a stable branch is more
important than making improvements. I'm even weary of updating the
raspberrypi firmware as I don't know how careful they are about
backwards compatibility. For kernel updates I do have an expectation
of backwards compatibility and an understanding that new stable
releases often fix security issues so I'm ok with those on stable
branches.

For example of where I'm concerned, a "raspberrypi2" override was
previously applied to both raspberrypi2 and raspberrypi3 machines.
After the third patch in this series it only applies to the
raspberrypi2 machine. Also, UBOOT_MACHINE is now set differently for
raspberrypi3 ('=' vs '?='). These changes may affect the value of some
variables when building for raspberrypi3 if downstream users haven't
explicitly handled both raspberrypi2 and raspberrypi3 overrides. I
don't mind these sorts of changes on the master branch but I worry
about applying them to a stable branch.

What do other meta-raspberrypi stable branch users think? Should we be
pedantic here or should we keep things open so that improvements can
be applied to stable branches?

Cheers,
Paul