drivers/usb/mon/mon_dma.c

   1 /*
   2  * The USB Monitor, inspired by Dave Harding's USBMon.
   3  *
   4  * mon_dma.c: Library which snoops on DMA areas.
   5  *
   6  * Copyright (C) 2005 Pete Zaitcev (zaitcev@redhat.com)
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/list.h>
  10 #include <linux/highmem.h>
  11 #include <asm/page.h>
  12
  13 #include <linux/usb.h>  /* Only needed for declarations in usb_mon.h */
  14 #include "usb_mon.h"
  15
  16 #ifdef __i386__         /* CONFIG_ARCH_I386 does not exit */
  17 #define MON_HAS_UNMAP 1
  18
  19 #define phys_to_page(phys)      pfn_to_page((phys) >> PAGE_SHIFT)
  20
  21 char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len)
  22 {
  23         struct page *pg;
  24         unsigned long flags;
  25         unsigned char *map;
  26         unsigned char *ptr;
  27
  28         /*
  29          * On i386, a DMA handle is the "physical" address of a page.
  30          * In other words, the bus address is equal to physical address.
  31          * There is no IOMMU.
  32          */
  33         pg = phys_to_page(dma_addr);
  34
  35         /*
  36          * We are called from hardware IRQs in case of callbacks.
  37          * But we can be called from softirq or process context in case
  38          * of submissions. In such case, we need to protect KM_IRQ0.
  39          */
  40         local_irq_save(flags);
  41         map = kmap_atomic(pg, KM_IRQ0);
  42         ptr = map + (dma_addr & (PAGE_SIZE-1));
  43         memcpy(dst, ptr, len);
  44         kunmap_atomic(map, KM_IRQ0);
  45         local_irq_restore(flags);
  46         return 0;
  47 }
  48 #endif /* __i386__ */
  49
  50 #ifndef MON_HAS_UNMAP
  51 char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len)
  52 {
  53         return 'D';
  54 }
  55 #endif