[Buildroot] [RFC 4/4] board/acmesystems/aria-g25: set BR2_GENIMAGE_CFG_FILES

[Andreas Naumann]

Hi,

Am 03.04.2017 um 15:54 schrieb Arnout Vandecappelle:
>
>
> On 03-04-17 15:01, Andreas Naumann wrote:
>>>> What I was thinking about in the past would be a deeper integration of genimage
>>>> in buildroots filesystem configuration, actually generating the genimage config.
>>>> But so far it was not worth the effort for me.
>>>
>>>  We have considered that in the past. The problem is that genimage doesn't
>>> support some of the options that we do. Otherwise, however, it would be really
>>
>> Are you refering to filesystem-specific options or missing ones like axfs,
>> cloop, cramfs?
>
>  I'm refering to filesystem-specific options. E.g. AFAIK genimage doesn't allow
> configuration of ext2 #inodes or reserved blocks, or UBIFS max LEB count or
> compression.

There is the option to supply extraargs to the mkfs tools of most of the 
filesystems. However some sizes and LEBs may remain 
hardcoded/calculated. Dont know if that would suffice.
>
>
>>> nice to remove all our messy filesystem handling code and just generate a
>>> genimage.cfg file...
>
>  And my point here is: we could just extend genimage with all those options.
> Then we can use genimage instead of our rootfs handling. For the most part, the
> rootfs infra could be reduced to a single genimage.cfg file.
>
>  But as usual: all that would be nice in a way, but doesn't give us any direct
> advantage over what we have now, and what we have now works.
>

ditto

>
>>>
>>>  OTOH we also considered that a full image typically needs more than just a
>>> single filesystem, so generating a genimage.cfg for part of the image seems a
>>> bit pointless.
>>
>> I dont quite understand. Do you mean combining e.g. a standard and a rescue system?
>
>  In practice, you rarely use the .ext2 or .ubifs image produced by Buildroot
> directly; instead, you'll embed it into a larger image that is a lot more
> complicated than e.g. the .ubi image offered by Buildroot (because you'd want a
> writeable data volume in addition to the ubifs rootfs).
>
>  So if we would use genimage for generating the .ext2 rootfs itself, then in
> practice you'll often end up running genimage twice: once for the .ext2 rootfs,
> and a second time to integrate it in a larger image.

I guess a good integration could avoid that, but I assume it would be 
difficult to predict the many ways people might want to customize this.

In addition I also think the practical problems of somehow having to 
convert Kconfig options to a genimage config are not worth it (even 
though augeas, which with I played lately, seems like it might provide 
an elegant way to do this.)

>
>
>  Coming back to the BR2_GENIMAGE_CFG_FILES option: actually it would make a
> whole lot more sense if the genimage were executed under fakeroot, because then
> we no longer need to generate the .ext2 subimage.
>
>  Still, there is hardly any advantage over having this as an explicit option
> rather than configuring
>
> BR2_ROOTFS_POST_FAKEROOT_SCRIPT="support/scripts/genimage.sh"
> BR2_ROOTFS_POST_SCRIPT_ARGS="-c path/to/my/genimage.cfg"

In fact, this is almost what i do right now. Just a rootfs.tar is 
created and subsequently processed by genimage (I have a small patch 
that allows genimage to be fed with a tar in additin to the input dir).


regards,
Andreas

>
>  Regards,
>  Arnout
>
>