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uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

Browse source 
https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>
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Anton Arapov 2021-04-03 12:58:10 +02:00 • committed by Alan Daniels
commit 56de2bcd43
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104
nixos/doc/manual/from_md/development/option-def.section.xml Normal file
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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-option-definitions">
<title>Option Definitions</title>
<para>
Option definitions are generally straight-forward bindings of values
to option names, like
</para>
<programlisting language="bash">
config = {
services.httpd.enable = true;
};
</programlisting>
<para>
However, sometimes you need to wrap an option definition or set of
option definitions in a <emphasis>property</emphasis> to achieve
certain effects:
</para>
<section xml:id="sec-option-definitions-delaying-conditionals">
<title>Delaying Conditionals</title>
<para>
If a set of option definitions is conditional on the value of
another option, you may need to use <literal>mkIf</literal>.
Consider, for instance:
</para>
<programlisting language="bash">
config = if config.services.httpd.enable then {
environment.systemPackages = [ ... ];
...
} else {};
</programlisting>
<para>
This definition will cause Nix to fail with an <quote>infinite
recursion</quote> error. Why? Because the value of
<literal>config.services.httpd.enable</literal> depends on the
value being constructed here. After all, you could also write the
clearly circular and contradictory:
</para>
<programlisting language="bash">
config = if config.services.httpd.enable then {
services.httpd.enable = false;
} else {
services.httpd.enable = true;
};
</programlisting>
<para>
The solution is to write:
</para>
<programlisting language="bash">
config = mkIf config.services.httpd.enable {
environment.systemPackages = [ ... ];
...
};
</programlisting>
<para>
The special function <literal>mkIf</literal> causes the evaluation
of the conditional to be <quote>pushed down</quote> into the
individual definitions, as if you had written:
</para>
<programlisting language="bash">
config = {
environment.systemPackages = if config.services.httpd.enable then [ ... ] else [];
...
};
</programlisting>
</section>
<section xml:id="sec-option-definitions-setting-priorities">
<title>Setting Priorities</title>
<para>
A module can override the definitions of an option in other
modules by setting a <emphasis>priority</emphasis>. All option
definitions that do not have the lowest priority value are
discarded. By default, option definitions have priority 1000. You
can specify an explicit priority by using
<literal>mkOverride</literal>, e.g.
</para>
<programlisting language="bash">
services.openssh.enable = mkOverride 10 false;
</programlisting>
<para>
This definition causes all other definitions with priorities above
10 to be discarded. The function <literal>mkForce</literal> is
equal to <literal>mkOverride 50</literal>.
</para>
</section>
<section xml:id="sec-option-definitions-merging">
<title>Merging Configurations</title>
<para>
In conjunction with <literal>mkIf</literal>, it is sometimes
useful for a module to return multiple sets of option definitions,
to be merged together as if they were declared in separate
modules. This can be done using <literal>mkMerge</literal>:
</para>
<programlisting language="bash">
config = mkMerge
[ # Unconditional stuff.
{ environment.systemPackages = [ ... ];
}
# Conditional stuff.
(mkIf config.services.bla.enable {
environment.systemPackages = [ ... ];
})
];
</programlisting>
</section>
</section>