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authorDuncan Sands <duncan.sands@math.u-psud.fr>2006-04-11 10:18:57 -0300
committerMauro Carvalho Chehab <mchehab@infradead.org>2006-05-12 19:54:50 -0300
commitbba3ad76a82eb458d31b136fa2414216e20c99cc (patch)
tree3b727a066fe78d7c88cf08c633d4b3887b0e1f37 /drivers
parent9175b8544ff7b73b158df370acc1d828b28b80b7 (diff)
V4L/DVB (3766): Correct buffer size calculations in cx88-core.c
The computation in cx88_risc_buffer suffers from the mistake: a non-zero padding value can cause more page borders to be crossed, leading to big buffer over-runs. This patch changes the additive constant from 3 + 4 to 4 It also changees the constant in cx88_risc_databuffer from 3 + 4 to 2, because 2 dwords are the correct vaule. Signed-off-by: Duncan Sands <baldrick@free.fr> Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/media/video/cx88/cx88-core.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/drivers/media/video/cx88/cx88-core.c b/drivers/media/video/cx88/cx88-core.c
index 2c3d9f1999b..e1092d5d462 100644
--- a/drivers/media/video/cx88/cx88-core.c
+++ b/drivers/media/video/cx88/cx88-core.c
@@ -146,9 +146,11 @@ int cx88_risc_buffer(struct pci_dev *pci, struct btcx_riscmem *risc,
fields++;
/* estimate risc mem: worst case is one write per page border +
- one write per scan line + syncs + jump (all 2 dwords) */
- instructions = (bpl * lines * fields) / PAGE_SIZE + lines * fields;
- instructions += 3 + 4;
+ one write per scan line + syncs + jump (all 2 dwords). Padding
+ can cause next bpl to start close to a page border. First DMA
+ region may be smaller than PAGE_SIZE */
+ instructions = fields * (1 + ((bpl + padding) * lines) / PAGE_SIZE + lines);
+ instructions += 2;
if ((rc = btcx_riscmem_alloc(pci,risc,instructions*8)) < 0)
return rc;
@@ -176,9 +178,11 @@ int cx88_risc_databuffer(struct pci_dev *pci, struct btcx_riscmem *risc,
int rc;
/* estimate risc mem: worst case is one write per page border +
- one write per scan line + syncs + jump (all 2 dwords) */
- instructions = (bpl * lines) / PAGE_SIZE + lines;
- instructions += 3 + 4;
+ one write per scan line + syncs + jump (all 2 dwords). Here
+ there is no padding and no sync. First DMA region may be smaller
+ than PAGE_SIZE */
+ instructions = 1 + (bpl * lines) / PAGE_SIZE + lines;
+ instructions += 1;
if ((rc = btcx_riscmem_alloc(pci,risc,instructions*8)) < 0)
return rc;