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Date:   Sun, 30 Aug 2020 11:13:53 +0200
From:   Greg Kroah-Hartman <>
To:     Alex Dewar <>
Cc:     "Rafael J. Wysocki" <>,
        Christian Brauner <>,
        "David S. Miller" <>,
        Nayna Jain <>,
        Dan Williams <>,
        Mauro Carvalho Chehab <>,
        Sourabh Jain <>,
Subject: Re: [PATCH RFC 2/2] sysfs: add helper macro for showing simple
 integer values

On Sun, Aug 30, 2020 at 12:37:17AM +0100, Alex Dewar wrote:
> sysfs attributes are supposed to be only single values, which are
> printed into a buffer of PAGE_SIZE. Accordingly, for many simple
> attributes, sprintf() can be used like so:
> 	static ssize_t my_show(..., char *buf)
> 	{
> 		...
> 		return sprintf("%d\n", my_integer);
> 	}
> The problem is that whilst this use of sprintf() is memory safe, other
> cases where e.g. a possibly unterminated string is passed as input, are
> not and so use of sprintf() here might make it more difficult to
> identify these problematic cases.
> Define a macro, sysfs_sprinti(), which outputs the value of a single
> integer to a buffer (with terminating "\n\0") and returns the size written.
> This way, we can convert over the some of the trivially correct users of
> sprintf() and decrease its usage in the kernel source tree.
> Another advantage of this approach is that we can now statically check
> the type of the integer so that e.g. an unsigned long long will be
> formatted as %llu. This will fix cases where the wrong format string has
> been passed to sprintf().
> Signed-off-by: Alex Dewar <>
> ---
>  include/linux/sysfs.h | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)

Did you try this out?  Don't you need to return the number of bytes

I like Joe's patches better, this feels like more work...


greg k-h

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