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>
diff --git a/drivers/media/video/cx88/cx88-core.c b/drivers/media/video/cx88/cx88-core.c
index 2c3d9f1..e1092d5 100644
--- a/drivers/media/video/cx88/cx88-core.c
+++ b/drivers/media/video/cx88/cx88-core.c
@@ -146,9 +146,11 @@
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 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;