From: Don Dutile <ddutile@redhat.com>
Date: Fri, 24 Apr 2009 14:31:02 -0400
Subject: [misc] make bus_find_device more robust, match upstream
Message-id: 49F20566.7030505@redhat.com
O-Subject: Re: [RHEL5.4 PATCH V2] Make bus_find_device() more robust to match upstream KVM device assignment use
Bugzilla: 492488
RH-Acked-by: Rik van Riel <riel@redhat.com>
RH-Acked-by: Markus Armbruster <armbru@redhat.com>

Don Dutile wrote:
> BZ 492488
>
> The following 3 file patch is a backport of the following
> 2 upstream patches.  The patch enables the following to
> work:
> 	echo 0000:01:00.0 > /sys/bus/pci/devices/0000:01:00.0/driver/unbind
>
> and not require a "-n" in the echo command to
> strip the trailing newline.
>
> This enables upstream scripts designed to do KVM device assignment
> to work on RHEL5 w/o adding a bunch of "-n" 's to these type of echo statements.
>
> Only built on x86_64 kernel.
> (it's architecture neutral).
> (sorry, no brew build since it was so trivial...).
>
>
> Tested during device assignments tests with VT-D testing on RHEL5.4.
> -- unbound a PCIe e1000e NIC card from a rhel5.4 host;
>    -- bound the e1000e device to a rhel5.3 guest
>
>
> Upstream patches:
> (1) http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=34990cf702
>
> 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>
> Acked-by: Greg KH <greg@kroah.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>
>
> (2) http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=3ce24d8d93
>
> Use sysfs_streq() in bus_find_device_by_name() so trailing newlines
> are ignored (E.G. in bind/unbind).
>
> Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
>
>
> NOTE: bus_find_device_by_name() is "driver_helper()" in RHEL5's driver/base/bus.c module.
>

Since the first 3 reviewers didn't like the format,
tweaked it to match upstream. ... a simple edit, as the original was.

Please (re-)review & ACK.

- Don

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 2beb313..6f7d9f5 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -141,9 +141,7 @@ static int driver_helper(struct device *dev, void *data)
 {
 	const char *name = data;
 
-	if (strcmp(name, dev->bus_id) == 0)
-		return 1;
-	return 0;
+	return sysfs_streq(name, dev->bus_id);
 }
 
 static ssize_t driver_unbind(struct device_driver *drv,
diff --git a/include/linux/string.h b/include/linux/string.h
index 7c88844..e5cc255 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -113,5 +113,7 @@ extern void argv_free(char **argv);
 }
 #endif
 
+extern bool sysfs_streq(const char *s1, const char *s2);
+
 #endif
 #endif /* _LINUX_STRING_H_ */
diff --git a/lib/string.c b/lib/string.c
index cbae612..479bc84 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -495,6 +495,33 @@ 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