From 9c97e588d82e90ca74488cd16e8f804cbec75978 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Fri, 12 Sep 2014 12:19:55 +0100 Subject: [PATCH] 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 Reviewed-by: H Hartley Sweeten Signed-off-by: Greg Kroah-Hartman --- .../staging/comedi/drivers/addi-data/addi_common.h | 2 +- drivers/staging/comedi/drivers/addi_apci_3120.c | 14 +++++++------- 2 files changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/staging/comedi/drivers/addi-data/addi_common.h b/drivers/staging/comedi/drivers/addi-data/addi_common.h index a7400a25f620..88295e40eb6a 100644 --- a/drivers/staging/comedi/drivers/addi-data/addi_common.h +++ b/drivers/staging/comedi/drivers/addi-data/addi_common.h @@ -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 */ diff --git a/drivers/staging/comedi/drivers/addi_apci_3120.c b/drivers/staging/comedi/drivers/addi_apci_3120.c index 2ac95bab195d..57c36ed9588c 100644 --- a/drivers/staging/comedi/drivers/addi_apci_3120.c +++ b/drivers/staging/comedi/drivers/addi_apci_3120.c @@ -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]); } } } -- 2.39.2