On 18/03/2016 13:58, Victor Wren wrote:
"Depends on: HAS_IOMEM [=y] && DRM [=y] && X86 [=y] && PCI [=y] &&
(AGP [=y] || AGP [=y]=n)"
Does that mean "don't care" or "preference for [y] but [n] will work,
or "if you set it [n] I'm gonna change it to [y]"?
According to
https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt,
the above expression is not really a boolean expression: it can return
three values : n (or 0), m (or 1), y (or2), and all its subexpressions can
also have three values.
The expression "e1 = e2 " evaluates to 0 if e1 is not equal to e2,
and 2 if e1 and e2 are equal.
The expression e1 && e2 means "min(e1,e2)".
The expression e1 || e2 means "max(e1,e2)".
a symbol is converted to its value, so:
- if you have not selected AGP, it is n
- if you have selected it as a module it is m
- if you have selected it to y it is y
so (AGP || AGP=n) means:
y if AGP=y or n
m if AGP=m
Now the whole expression means :
if any symbol (aside of AGP) is n : the expression is n
(the symbol is not shown)
if some or all symbols are m and others are y : the
symbol is shown with angle brackets, and you can
select only as m
if all symbols are y, but AGP is y or n: the symbol is
shown with square brackets, and you can select it
with y or m.
Regards
Pierre
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