[alsa-devel] [PATCH] fix incorrect rounding direction in snd_interval_ratnum()

[Krzysztof Helt]

From: Krzysztof Helt <krzysztof.h1 at wp.pl>

The direction of rounding is incorrect in the snd_interval_ratnum()
It was detected with following parameters (sb8 driver playing
8kHz stereo file):
 - num is always 1000000
 - requested frequency rate is from 7999 to 7999 (single frequency)

The first loop calculates div_down(num, freq->min) which is 125.
Thus, a frequency range's minimum value is 1000000 / 125 = 8000 Hz.
The second loop calculates div_up(num, freq->max) which is 126
The frequency range's maximum value is 1000000 / 126 = 7936 Hz.
The range maximum is lower than the range minimum so the function
fails due to empty result range.

Signed-off-by: Krzysztof Helt <krzysztof.h1 at wp.pl>
---
 sound/core/pcm_lib.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 30f4108..a27545b 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -758,7 +758,7 @@ int snd_interval_ratnum(struct snd_interval *i,
 		int diff;
 		if (q == 0)
 			q = 1;
-		den = div_down(num, q);
+		den = div_up(num, q);
 		if (den < rats[k].den_min)
 			continue;
 		if (den > rats[k].den_max)
@@ -794,7 +794,7 @@ int snd_interval_ratnum(struct snd_interval *i,
 			i->empty = 1;
 			return -EINVAL;
 		}
-		den = div_up(num, q);
+		den = div_down(num, q);
 		if (den > rats[k].den_max)
 			continue;
 		if (den < rats[k].den_min)
-- 
1.6.4


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