Messages in this thread Patch in this message | | | From | David Brownell <> | Subject | Re: [patch/rfc 2.6.25-git] gpio: sysfs interface | Date | Tue, 29 Apr 2008 11:45:13 -0700 |
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On Monday 28 April 2008, Greg KH wrote: > On Mon, Apr 28, 2008 at 07:54:55PM -0700, Andrew Morton wrote: > > On Mon, 28 Apr 2008 16:28:13 -0700 David Brownell <david-b@pacbell.net> wrote: > > > > > > If we had a strcmp() variant which treats a \n in the first arg as a \0 > > > > the above would become > > > > > > > > if (sysfs_streq(buf, "high")) > > > > status = gpio_direction_output(gpio, 1); > > > > else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low")) > > > > status = gpio_direction_output(gpio, 0); > > > > else if (sysfs_streq(buf, "in")) > > > > status = gpio_direction_input(gpio); > > > > > > That would indeed be better. Maybe I should whip up a sysfs > > > patch adding that, and have this depend on that patch. (I've > > > CC'd Greg in case he has comments on that...) > > > > Yes, it would be a standalone patch. The sort which generates oceans of > > useful feedback ;) The sort which also generates hundreds of > > use-new-toy-to-clean-up-old-code patches for me to merge :( > > Heh, sounds good to me :)
Hard to say where should live, but lib/strings.c seemed fair. See the appended patch. I made it not care which string has newline termination, since caring seems very error-prone.
- Dave
========= CUT HERE Add a new sysfs_streq() string comparison function, which ignores the trailing newlines found in sysfs inputs. By example:
sysfs_streq("a", "b") ==> false sysfs_streq("a", "a") ==> true sysfs_streq("a", "a\n") ==> true sysfs_streq("a\n", "a") ==> true
This is intended to simplify parsing of sysfs inputs, letting them avoid the need to manually strip off newlines from inputs.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> --- include/linux/string.h | 2 ++ lib/string.c | 27 +++++++++++++++++++++++++++ 2 files changed, 29 insertions(+)
--- g26.orig/include/linux/string.h 2008-04-29 05:45:53.000000000 -0700 +++ g26/include/linux/string.h 2008-04-29 05:55:14.000000000 -0700 @@ -109,5 +109,7 @@ extern void *kmemdup(const void *src, si extern char **argv_split(gfp_t gfp, const char *str, int *argcp); extern void argv_free(char **argv); +extern bool sysfs_streq(const char *s1, const char *s2); + #endif #endif /* _LINUX_STRING_H_ */ --- g26.orig/lib/string.c 2008-04-29 05:15:52.000000000 -0700 +++ g26/lib/string.c 2008-04-29 05:55:32.000000000 -0700 @@ -493,6 +493,33 @@ char *strsep(char **s, const char *ct) EXPORT_SYMBOL(strsep); #endif +/** + * sysfs_streq - return true if strings are equal, modulo trailing newline + * @s1: one string + * @s2: another string + * + * This routine returns true iff two strings are equal, treating both + * NUL and newline-then-NUL as equivalent string terminations. It's + * geared for use with sysfs input strings, which generally terminate + * with newlines but are compared against values without newlines. + */ +bool sysfs_streq(const char *s1, const char *s2) +{ + while (*s1 && *s1 == *s2) { + s1++; + s2++; + } + + if (*s1 == *s2) + return true; + if (!*s1 && *s2 == '\n' && !s2[1]) + return true; + if (*s1 == '\n' && !s1[1] && !*s2) + return true; + return false; +} +EXPORT_SYMBOL(sysfs_streq); + #ifndef __HAVE_ARCH_MEMSET /** * memset - Fill a region of memory with the given value
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