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Commit 9c97e588 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman
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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: default avatarIan Abbott <abbotti@mev.co.uk>
Reviewed-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent df567feb

drivers/staging/comedi/drivers/addi-data/addi_common.h

+1 −1
Original line number Diff line number Diff line
@@ -110,7 +110,7 @@ struct addi_private { 
	unsigned int ul_DmaBufferHw[2];	/*  hw address of DMA buff */

	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_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_OutputMemoryStatus;

	unsigned char b_TimerSelectMode;	/*  Contain data written at iobase + 0C */

drivers/staging/comedi/drivers/addi_apci_3120.c

+7 −7
Original line number Diff line number Diff line
@@ -57,7 +57,7 @@ static int apci3120_auto_attach(struct comedi_device *dev, 
	const struct addi_board *this_board = NULL;

	struct addi_private *devpriv;

	struct comedi_subdevice *s;

	int ret, pages, i;

	int ret, order, i;



	if (context < ARRAY_SIZE(apci3120_boardtypes))

		this_board = &apci3120_boardtypes[context];
@@ -93,17 +93,17 @@ static int apci3120_auto_attach(struct comedi_device *dev, 
	/* Allocate DMA buffers */

	devpriv->b_DmaDoubleBuffer = 0;

	for (i = 0; i < 2; i++) {

		for (pages = 4; pages >= 0; pages--) {

		for (order = 2; order >= 0; order--) {

			devpriv->ul_DmaBufferVirtual[i] =

				(void *) __get_free_pages(GFP_KERNEL, pages);

			    (void *)__get_free_pages(GFP_KERNEL, order);



			if (devpriv->ul_DmaBufferVirtual[i])

				break;

		}

		if (!devpriv->ul_DmaBufferVirtual[i])

			break;

		devpriv->ui_DmaBufferPages[i] = pages;

		devpriv->ui_DmaBufferSize[i] = PAGE_SIZE * pages;

		devpriv->ui_DmaBufferPageOrder[i] = order;

		devpriv->ui_DmaBufferSize[i] = PAGE_SIZE << order;

		devpriv->ul_DmaBufferHw[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]) {

			free_pages((unsigned long)devpriv->

				ul_DmaBufferVirtual[0],

				devpriv->ui_DmaBufferPages[0]);

				devpriv->ui_DmaBufferPageOrder[0]);

		}

		if (devpriv->ul_DmaBufferVirtual[1]) {

			free_pages((unsigned long)devpriv->

				ul_DmaBufferVirtual[1],

				devpriv->ui_DmaBufferPages[1]);

				devpriv->ui_DmaBufferPageOrder[1]);

		}

	}

}