From: Duncan Sands Date: Tue, 11 Apr 2006 13:18:57 +0000 (-0300) Subject: V4L/DVB (3766): Correct buffer size calculations in cx88-core.c X-Git-Tag: v2.6.17-rc5~31^2~22 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bba3ad76a82eb458d31b136fa2414216e20c99cc;p=linux-2.6 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 Signed-off-by: Mauro Carvalho Chehab --- diff --git a/drivers/media/video/cx88/cx88-core.c b/drivers/media/video/cx88/cx88-core.c index 2c3d9f1999..e1092d5d46 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;