linux-kernel - Re: [PATCH v2 1/4] lib/string_helpers: export string_units

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Date:	Fri, 22 Jan 2016 21:13:19 -0800
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-efi@...r.kernel.org,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] lib/string_helpers: export string_units_{2,10}
 for others

On Thu, 2016-01-21 at 17:22 +0200, Andy Shevchenko wrote:
> There is one user coming which would like to use those string arrays.
> It might
> be useful for any other user in the future.

Well, let's not do it until we have an actual consumer because that
will help us get the interface correct.

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  include/linux/string_helpers.h |  6 ++++++
>  lib/string_helpers.c           | 21 ++++++++++++---------
>  2 files changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/string_helpers.h
> b/include/linux/string_helpers.h
> index dabe643..a55c9cc 100644
> --- a/include/linux/string_helpers.h
> +++ b/include/linux/string_helpers.h
> @@ -10,6 +10,12 @@ enum string_size_units {
>  	STRING_UNITS_2,		/* use binary powers of 2^10
> */
>  };
>  
> +#define STRING_UNITS_10_NUM	9
> +#define STRING_UNITS_2_NUM	9
> +
> +extern const char *const string_units_10[STRING_UNITS_10_NUM];
> +extern const char *const string_units_2[STRING_UNITS_2_NUM];
> +
>  void string_get_size(u64 size, u64 blk_size, enum string_size_units
> units,
>  		     char *buf, int len);
>  
> diff --git a/lib/string_helpers.c b/lib/string_helpers.c
> index 5939f63..7ee4644 100644
> --- a/lib/string_helpers.c
> +++ b/lib/string_helpers.c
> @@ -13,6 +13,15 @@
>  #include <linux/string.h>
>  #include <linux/string_helpers.h>
>  
> +const char * const string_units_10[STRING_UNITS_10_NUM] = {
> +	"B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB",
> +};
> +EXPORT_SYMBOL(string_units_10);
> +const char * const string_units_2[STRING_UNITS_2_NUM] = {
> +	"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB",
> +};
> +EXPORT_SYMBOL(string_units_2);
> +

This is a pretty silly thing to do; how does someone who adds a unit to
one of the string_units know to increment STRING_UNITS_X_NUM?  Even if
you add a comment admonishing them to do it, it's far better to have
this calculated at compile time like it was before this patch.

James