The last parameter of `__get_free_pages()` is log2 (the 'order') of the
number of pages to be allocated. This driver seems to think it is the
linear number of pages, so `pci9118_alloc_dma()` first tries to allocate
16 pages, but only uses 4 of them, setting the buffer size to PAGE_SIZE
multiplied by the 'order'. If the allocation fails, it tries
progressively smaller orders, down to 0. If the allocation at order 0
succeeds, the buffer size is set to 0, which is likely to cause
problems.
Set the buffer size to `PAGE_SIZE` shifted left by the allocation order.
Since the maximum buffer size previously used was 4, start with an
allocation order of 2 instead of 4. Rename the `pages` member of
`struct pci9118_dmabuf` (and the local variable in
`pci9118_alloc_dma()`) to `order` to make it clearer what it is.
Signed-off-by: Ian Abbott <abbo...@mev.co.uk>
---
drivers/staging/comedi/drivers/adl_pci9118.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/staging/comedi/drivers/adl_pci9118.c
b/drivers/staging/comedi/drivers/adl_pci9118.c
index 1169104..6ab9e0a 100644
--- a/drivers/staging/comedi/drivers/adl_pci9118.c
+++ b/drivers/staging/comedi/drivers/adl_pci9118.c
@@ -208,7 +208,7 @@ struct pci9118_dmabuf {
unsigned long hw; /* hardware (bus) address of buffer */
unsigned int size; /* size of dma buffer in bytes */
unsigned int use_size; /* which size we may now use for transfer */
- int pages; /* number of pages in buffer */
+ int order; /* log2 number of pages in buffer */
};
struct pci9118_private {
@@ -1479,20 +1479,20 @@ static void pci9118_alloc_dma(struct comedi_device *dev)
{
struct pci9118_private *devpriv = dev->private;
struct pci9118_dmabuf *dmabuf;
- int pages;
+ int order;
int i;
for (i = 0; i < 2; i++) {
dmabuf = &devpriv->dmabuf[i];
- for (pages = 4; pages >= 0; pages--) {
- dmabuf->virt = __get_free_pages(GFP_KERNEL, pages);
+ for (order = 2; order >= 0; order--) {
+ dmabuf->virt = __get_free_pages(GFP_KERNEL, order);
if (dmabuf->virt)
break;
}
if (!dmabuf->virt)
break;
- dmabuf->pages = pages;
- dmabuf->size = PAGE_SIZE * pages;
+ dmabuf->order = order;
+ dmabuf->size = PAGE_SIZE << order;
dmabuf->hw = virt_to_bus((void *)dmabuf->virt);
if (i == 0)
@@ -1514,7 +1514,7 @@ static void pci9118_free_dma(struct comedi_device *dev)
for (i = 0; i < 2; i++) {
dmabuf = &devpriv->dmabuf[i];
if (dmabuf->virt)
- free_pages(dmabuf->virt, dmabuf->pages);
+ free_pages(dmabuf->virt, dmabuf->order);
}
}
--
2.1.0
--
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