As previously explained, entry dependencies can be specified in the form of logical clauses based on a syntax similar to C. A dependency specification must be structured as follows:

depends [on] <expr> <expr> ::= <Symbol>

<Symbol> '=' <Symbol> <Symbol> '!=' <Symbol>

'(' <expr> ')' '!' <expr> <expr> '&&' <expr> <expr> '||' <expr>

The possible expressions are listed in the order in which they are interpreted. In other words, the expressions listed first have a higher priority than those that follow.

The meaning of the operations is the same as in the C syntax: y = 2, n = 0, and m = 1. A menu item is not visible unless the result of the dependency calculation is not 0.

A particular dependency is specified by ''experimental.'' Drivers still in the experimental stage must be labeled with this dependency (as a && logical operation if the driver has other dependencies of its own). Because the kernel provides a configuration option in init/Kconfig to allow users to set the symbol to y or n (Prompt for development and/or incomplete code/drivers), it is easy to remove drivers of this kind from the configuration options for those users who crave stability. The string '' (Experimental) '' should appear at the end to indicate that the driver code is in fact experimental.

Continue reading here: B23 Processing Configuration Information

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