[PATCH v5] ALSA: control: Fix parsing of numeric fields

[Sreeraj S Kurup <sreekuttan2156239@gmail.com>]

parse_uint() passes the remaining input string to kstrtoull().

When the input contains comma-separated fields, the string
contains both the numeric value and the following fields.

For example, with:

device=1,subdevice=0,name=Master

kstrtoull() receives "1,subdevice=0,name=Master" and fails
to parse the numeric value.

Stop parsing at the next comma and pass only the numeric
field to kstrtouint().

Make all parse_*() functions return the end of the current
substring, leaving delimiter handling to set_led_id().
Temporarily terminate the numeric substring in parse_uint()
before calling kstrtouint().

This allows numeric fields to be parsed correctly in
comma-separated input.

Fixes: a135dfb5de15 ("ALSA: led control - add sysfs kcontrol LED marking layer")
Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
v5:
 - Advance past the closing quote in the quoted-string
   branch of parse_string().
 - Ensure parse_string() returns the end of the current
   substring for both quoted and unquoted strings.
v4:
 - Make parse_*() functions consistently return the end of
   the current substring.
 - Let set_led_id() handle comma advancement.
 - Use kstrtouint() after temporarily terminating the
   numeric substring.
v3:
 - No code changes. Retain the v2 implementation after
   comparing the alternative approaches.
v2:
 - Add the Fixes trailer.

 sound/core/control_led.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/sound/core/control_led.c b/sound/core/control_led.c
index 501387287ae6..1aadacfbd3c4 100644
--- a/sound/core/control_led.c
+++ b/sound/core/control_led.c
@@ -447,22 +447,23 @@ static const struct attribute_group *snd_ctl_led_dev_attr_groups[] = {
 	NULL,
 };
 
+/* return the end of substring pointing to either comma or NUL */
 static char *find_eos(char *s)
 {
 	while (*s && *s != ',')
 		s++;
-	if (*s)
-		s++;
 	return s;
 }
 
 static char *parse_uint(char *s, unsigned int *val)
 {
-	unsigned long long res;
-	if (kstrtoull(s, 10, &res))
-		res = 0;
-	*val = res;
-	return find_eos(s);
+	char *end = find_eos(s);
+	char delimiter = *end;
+	*end = '\0';
+	if (kstrtouint(s, 10, val))
+		*val = 0;
+	*end = delimiter;
+	return end;
 }
 
 static char *parse_string(char *s, char *val, size_t val_size)
@@ -477,6 +478,8 @@ static char *parse_string(char *s, char *val, size_t val_size)
 			}
 			s++;
 		}
+		if (*s)
+			s++;
 	} else {
 		while (*s && *s != ',') {
 			if (val_size > 1) {
@@ -487,8 +490,6 @@ static char *parse_string(char *s, char *val, size_t val_size)
 		}
 	}
 	*val = '\0';
-	if (*s)
-		s++;
 	return s;
 }
 
-- 
2.55.0