* Re: old bug in au88x0_core.c
2016-06-27 13:03 old bug in au88x0_core.c Dan Carpenter
@ 2016-06-29 13:40 ` Takashi Iwai
0 siblings, 0 replies; 2+ messages in thread
From: Takashi Iwai @ 2016-06-29 13:40 UTC (permalink / raw)
To: Dan Carpenter; +Cc: alsa-devel
On Mon, 27 Jun 2016 15:03:47 +0200,
Dan Carpenter wrote:
>
> Hi ALSA devs,
>
> The patch 1da177e4c3f4: "Linux-2.6.12-rc2" from Apr 16, 2005, leads
> to the following static checker warning:
>
> sound/pci/au88x0/au88x0_core.c:1449 vortex_wtdma_bufshift()
> warn: mask and shift to zero
>
> sound/pci/au88x0/au88x0_core.c
> 1441 static int vortex_wtdma_bufshift(vortex_t * vortex, int wtdma)
> 1442 {
> 1443 stream_t *dma = &vortex->dma_wt[wtdma];
> 1444 int page, p, pp, delta, i;
> 1445
> 1446 page =
> 1447 (hwread(vortex->mmio, VORTEX_WTDMA_STAT + (wtdma << 2)) &
> 1448 WT_SUBBUF_MASK)
> 1449 >> WT_SUBBUF_SHIFT;
>
> This is always zero because:
>
> #define WT_SUBBUF_MASK 0x3
> #define WT_SUBBUF_SHIFT 0x15
>
> 1450 if (dma->nr_periods >= 4)
> 1451 delta = (page - dma->period_real) & 3;
> 1452 else {
> 1453 delta = (page - dma->period_real);
> 1454 if (delta < 0)
> 1455 delta += dma->nr_periods;
> 1456 }
> 1457 if (delta == 0)
> 1458 return 0;
>
>
> 1493 #if 0
> 1494 static void
> 1495 vortex_wtdma_getposition(vortex_t * vortex, int wtdma, int *subbuf, int *pos)
> 1496 {
> 1497 int temp;
> 1498 temp = hwread(vortex->mmio, VORTEX_WTDMA_STAT + (wtdma << 2));
> 1499 *subbuf = (temp >> WT_SUBBUF_SHIFT) & WT_SUBBUF_MASK;
>
> >From this ifdef zero code, it looks like we should shift first then do
> the mask.
>
> 1500 *pos = temp & POS_MASK;
> 1501 }
> 1502
> 1503 static int vortex_wtdma_getcursubuffer(vortex_t * vortex, int wtdma)
> 1504 {
> 1505 return ((hwread(vortex->mmio, VORTEX_WTDMA_STAT + (wtdma << 2)) >>
> 1506 POS_SHIFT) & POS_MASK);
> 1507 }
> 1508 #endif
Correct, this should be fixed in that way. Below is the fix patch I'm
going to queue.
thanks,
Takashi
-- 8< --
From: Takashi Iwai <tiwai@suse.de>
Subject: [PATCH] ALSA: au88x0: Fix calculation in vortex_wtdma_bufshift()
vortex_wtdma_bufshift() function does calculate the page index
wrongly, first masking then shift, which always results in zero.
The proper computation is to first shift, then mask.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/pci/au88x0/au88x0_core.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/sound/pci/au88x0/au88x0_core.c b/sound/pci/au88x0/au88x0_core.c
index 4a054d720112..d3125c169684 100644
--- a/sound/pci/au88x0/au88x0_core.c
+++ b/sound/pci/au88x0/au88x0_core.c
@@ -1444,9 +1444,8 @@ static int vortex_wtdma_bufshift(vortex_t * vortex, int wtdma)
int page, p, pp, delta, i;
page =
- (hwread(vortex->mmio, VORTEX_WTDMA_STAT + (wtdma << 2)) &
- WT_SUBBUF_MASK)
- >> WT_SUBBUF_SHIFT;
+ (hwread(vortex->mmio, VORTEX_WTDMA_STAT + (wtdma << 2))
+ >> WT_SUBBUF_SHIFT) & WT_SUBBUF_MASK;
if (dma->nr_periods >= 4)
delta = (page - dma->period_real) & 3;
else {
--
2.9.0
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