[OE-core] defining a new image: inherit "image" vs "image_types"?

[Robert P. J. Day]

On Thu, 10 Jan 2013, Martin Jansa wrote:

> On Thu, Jan 10, 2013 at 08:31:52AM -0500, Robert P. J. Day wrote:
> >
> >   possibly a distinction with no distinction but i wanted to throw
> > together a page on how one defines a new "image type" -- most
> > commonly, an SD card image -- and i started with what comes with the
> > meta-raspberrypi layer, which seems to work just fine.
> >
> >   what i noticed is that that layer introduces the new
> > "sdcard_image-rpi.bbclass" class file, which opens with:
> >
> > inherit image_types
> >
> >   but then i remembered that the meta-ti layer does the same thing,
> > providing the new class file "sdcard_image.bbclass" which opens
> > instead with:
> >
> > inherit image
> >
> >   i realize that the oe-core image.bbclass contains this snippet:
> >
> > IMAGE_CLASSES ?= "image_types"
> > inherit ${IMAGE_CLASSES}
> >
> > so it's clear that inheriting "image" is sufficient, but the
> > alternative *isn't* clear.
> >
> >   what's the preferred construction here?  before digging further to
> > see if there's something subtle or equivalent happening, should it be
> > sufficient for new image definitions to simply:
> >
> > inherit image_types
> >
> > ??  have i just not RTFS far enough to see that there's no difference?
>
> did you read image_types.bbclass?

  in fact, i'm reading it now, after verifying that the meta-ti layer
appears to be incorrect.  so i think that answers my question.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
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