[yocto] observations on bitbake user manual, chapter 2

[Robert P. J. Day]

  more random thoughts ...

intro:

 in the note: "Prior to executing BitBake, you should take advantage
of available parallel thread execution on your build host by setting
the BB_NUMBER_THREADS variable in your project's local.conf
configuration file. "

  as in chapter 1, i think there will be some confusion since the
bitbake manual seems to jump between what you will see WRT bitbake in
a *direct* checkout, and what you will more likely see if you've
checked out poky.  as you well know, in the poky checkout,
bitbake.conf is considerably enhanced and already contains:

  # Default to setting automatically based on cpu count
  BB_NUMBER_THREADS ?= "${@oe.utils.cpu_count()}"

  # Default to setting automatically based on cpu count
  PARALLEL_MAKE ?= "-j ${@oe.utils.cpu_count()}"

and while i understand that the bitbake manual is meant to be build
system agnostic, i think trying too hard to do that is going to make
part of it unnecessarily confusing.

  oh, and that note mentions BB_NUMBER_THREADS while saying nothing
about PARALLEL_MAKE, which seems odd.

2.3 Providers

  while this section describes how a recipe can *extend* the things it
provides with "+=", it might be worth mentioning how it can simply
override what it provides with

  PROVIDES = "..."

  this is fairly common with libraries, as in:

meta/recipes-graphics/xorg-lib/libxext_git.bb:PROVIDES = "xext"
meta/recipes-graphics/xorg-lib/libxxf86misc_1.0.3.bb:PROVIDES = "xxf86misc"
meta/recipes-graphics/xorg-lib/libx11.inc:PROVIDES = "virtual/libx11"
meta/recipes-graphics/xorg-lib/libxmu_1.1.2.bb:PROVIDES = "xmu"
meta/recipes-graphics/xorg-lib/libxext_1.3.3.bb:PROVIDES = "xext"
meta/recipes-graphics/xorg-lib/libxdamage_1.1.4.bb:PROVIDES = "xdamage"
meta/recipes-graphics/xorg-lib/libxdmcp_1.1.1.bb:PROVIDES = "xdmcp"

2.4 Preferences

  if i remember this correctly, there is nothing special about a
preferred provider containing a slash, such as "virtual/kernel", is
there? that might be worth mentioning here.

  also, in note, busybox is now up to 1.23.1, not 1.22.1.

2.7 Executing Tasks

  with text like "${T}/log.do_taskname.pid", the "taskname" part
should be tagged with something like <replaceable> to show that it is
not verbatim.

  that's it for chapter 2 ...

rday

-- 

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

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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