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staging: comedi: addi_apci_3120: don't overallocate DMA buffer 

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 `apci3120_auto_attach()` 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 `ui_DmaBufferPages` member of
`struct addi_private` to `ui_DmaBufferPageOrder` and rename the `pages`
local variable to `order` to make it clearer what it is.

Note: `struct addi_private` is used by some other ADDI-DATA drivers as
well, but this is the only one using the affected members.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2014-09-12 12:19:55 +01:00 committed by Greg Kroah-Hartman
parent df567feb00
commit 9c97e588d8
2 changed files with 8 additions and 8 deletions
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2
drivers/staging/comedi/drivers/addi-data/addi_common.h
View File

@ -110,7 +110,7 @@ struct addi_private {
unsigned int ul_DmaBufferHw[2]; /* hw address of DMA buff */ unsigned int ul_DmaBufferHw[2]; /* hw address of DMA buff */
unsigned int ui_DmaBufferSize[2]; /* size of dma buffer in bytes */ unsigned int ui_DmaBufferSize[2]; /* size of dma buffer in bytes */
unsigned int ui_DmaBufferUsesize[2]; /* which size we may now used for transfer */ unsigned int ui_DmaBufferUsesize[2]; /* which size we may now used for transfer */
unsigned int ui_DmaBufferPages[2]; /* number of pages in buffer */ unsigned int ui_DmaBufferPageOrder[2]; /* log2 of pages in buffer */
unsigned char b_DigitalOutputRegister; /* Digital Output Register */ unsigned char b_DigitalOutputRegister; /* Digital Output Register */
unsigned char b_OutputMemoryStatus; unsigned char b_OutputMemoryStatus;
unsigned char b_TimerSelectMode; /* Contain data written at iobase + 0C */ unsigned char b_TimerSelectMode; /* Contain data written at iobase + 0C */

14
drivers/staging/comedi/drivers/addi_apci_3120.c
View File

@ -57,7 +57,7 @@ static int apci3120_auto_attach(struct comedi_device *dev,
const struct addi_board *this_board = NULL; const struct addi_board *this_board = NULL;
struct addi_private *devpriv; struct addi_private *devpriv;
struct comedi_subdevice *s; struct comedi_subdevice *s;
int ret, pages, i; int ret, order, i;
if (context < ARRAY_SIZE(apci3120_boardtypes)) if (context < ARRAY_SIZE(apci3120_boardtypes))
this_board = &apci3120_boardtypes[context]; this_board = &apci3120_boardtypes[context];
@ -93,17 +93,17 @@ static int apci3120_auto_attach(struct comedi_device *dev,
/* Allocate DMA buffers */ /* Allocate DMA buffers */
devpriv->b_DmaDoubleBuffer = 0; devpriv->b_DmaDoubleBuffer = 0;
for (i = 0; i < 2; i++) { for (i = 0; i < 2; i++) {
for (pages = 4; pages >= 0; pages--) { for (order = 2; order >= 0; order--) {
devpriv->ul_DmaBufferVirtual[i] = devpriv->ul_DmaBufferVirtual[i] =
(void *) __get_free_pages(GFP_KERNEL, pages); (void *)__get_free_pages(GFP_KERNEL, order);
if (devpriv->ul_DmaBufferVirtual[i]) if (devpriv->ul_DmaBufferVirtual[i])
break; break;
} }
if (!devpriv->ul_DmaBufferVirtual[i]) if (!devpriv->ul_DmaBufferVirtual[i])
break; break;
devpriv->ui_DmaBufferPages[i] = pages; devpriv->ui_DmaBufferPageOrder[i] = order;
devpriv->ui_DmaBufferSize[i] = PAGE_SIZE * pages; devpriv->ui_DmaBufferSize[i] = PAGE_SIZE << order;
devpriv->ul_DmaBufferHw[i] = devpriv->ul_DmaBufferHw[i] =
virt_to_bus(devpriv->ul_DmaBufferVirtual[i]); virt_to_bus(devpriv->ul_DmaBufferVirtual[i]);
} }
@ -201,12 +201,12 @@ static void apci3120_detach(struct comedi_device *dev)
if (devpriv->ul_DmaBufferVirtual[0]) { if (devpriv->ul_DmaBufferVirtual[0]) {
free_pages((unsigned long)devpriv-> free_pages((unsigned long)devpriv->
ul_DmaBufferVirtual[0], ul_DmaBufferVirtual[0],
devpriv->ui_DmaBufferPages[0]); devpriv->ui_DmaBufferPageOrder[0]);
} }
if (devpriv->ul_DmaBufferVirtual[1]) { if (devpriv->ul_DmaBufferVirtual[1]) {
free_pages((unsigned long)devpriv-> free_pages((unsigned long)devpriv->
ul_DmaBufferVirtual[1], ul_DmaBufferVirtual[1],
devpriv->ui_DmaBufferPages[1]); devpriv->ui_DmaBufferPageOrder[1]);
} }
} }
} }