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List:       xen-devel
Subject:    Re: [Xen-devel] [PATCH v6 1/3] Kconfig: import kconfig.h from Linux 4.3
From:       Doug Goldstein <cardoe () cardoe ! com>
Date:       2016-01-31 4:08:15
Message-ID: 56AD88AF.5020800 () cardoe ! com
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On 1/30/16 3:47 AM, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> To support using CONFIG_ options in C/CPP expressions, import kconfig.h
> from the Linux v4.3 tag (commit id
> 6a13feb9c82803e2b815eca72fa7a9f5561d7861).
> Only import IS_ENABLED for Xen since Xen doesn't support loadable
> modules.
> 
> CC: Doug Goldstein <cardoe@cardoe.com>
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>

Reviewed-by: Doug Goldstein <cardoe@cardoe.com>

> ---
>  xen/include/xen/kconfig.h | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>  create mode 100644 xen/include/xen/kconfig.h
> 
> diff --git a/xen/include/xen/kconfig.h b/xen/include/xen/kconfig.h
> new file mode 100644
> index 0000000..4d58c5b
> --- /dev/null
> +++ b/xen/include/xen/kconfig.h
> @@ -0,0 +1,31 @@
> +#ifndef __XEN_KCONFIG_H
> +#define __XEN_KCONFIG_H
> +
> +#include <generated/autoconf.h>
> +
> +/*
> + * Helper macros to use CONFIG_ options in C/CPP expressions. Note that
> + * these only work with boolean option.
> + */
> +
> +/*
> + * Getting something that works in C and CPP for an arg that may or may
> + * not be defined is tricky.  Here, if we have "#define CONFIG_BOOGER 1"
> + * we match on the placeholder define, insert the "0," for arg1 and generate
> + * the triplet (0, 1, 0).  Then the last step cherry picks the 2nd arg (a one).
> + * When CONFIG_BOOGER is not defined, we generate a (... 1, 0) pair, and when
> + * the last step cherry picks the 2nd arg, we get a zero.
> + */
> +#define __ARG_PLACEHOLDER_1 0,
> +#define config_enabled(cfg) _config_enabled(cfg)
> +#define _config_enabled(value) __config_enabled(__ARG_PLACEHOLDER_##value)
> +#define __config_enabled(arg1_or_junk) ___config_enabled(arg1_or_junk 1, 0)
> +#define ___config_enabled(__ignored, val, ...) val
> +
> +/*
> + * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y', 0
> + * otherwise.
> + */
> +#define IS_ENABLED(option) config_enabled(option)
> +
> +#endif /* __XEN_KCONFIG_H */
> 


-- 
Doug Goldstein


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