Re: [PATCH 1/3] command: introduce abi version

[Johannes Stezenbach <js@sig21.net>]

On Mon, Oct 29, 2012 at 09:50:55AM +0100, Sascha Hauer wrote:
> On Mon, Oct 22, 2012 at 06:07:26PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > This will allow to detect incompatibility between the env abi and the current
> > barebox one
...
> > +
> > +#define COMMAND_ABI_VERSION	0
> 
> Please describe what this is. Something like:
> 
> /*
>  * This tracks incompatible changes to the barebox command interface.
>  * This number is increased when changes are introduced which will cause
>  * an older environment to no longer work. This could be:
>  *
>  * - changes in commandline options to commands
>  * - renames of commands
>  * - rename of device files
>  *
>  * If you change this value, add a explanation of the actual change to
>  * Documentation/command-abi-changes.txt
>  */

I wonder how this will work in practice.  If I use a simple
/env/bin/init script and someone makes changes to a command
which isn't used by my /env/bin/init, will it still cause
my environment to be detected as incompatible?

Maybe it would be a good idea to give the user control
over when to change COMMAND_ABI_VERSION by putting it into menuconfig?

Either way I guess it means the default environment's init script
would need to implement automatic update to not lose important  settings.

Bottom line: It's much better to not make incompatible ABI changes _ever_.


Johannes

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