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 /*
  17  * PC-compatibles, are, fortunately, sufficiently cache-coherent for this.
  18  */
  19 #if defined(__i386__) || defined(__x86_64__) /* CONFIG_ARCH_I386 doesn't exit */
  20 #define MON_HAS_UNMAP 1
  21
  22 #define phys_to_page(phys)      pfn_to_page((phys) >> PAGE_SHIFT)
  23
  24 char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len)
  25 {
  26         struct page *pg;
  27         unsigned long flags;
  28         unsigned char *map;
  29         unsigned char *ptr;
  30
  31         /*
  32          * On i386, a DMA handle is the "physical" address of a page.
  33          * In other words, the bus address is equal to physical address.
  34          * There is no IOMMU.
  35          */
  36         pg = phys_to_page(dma_addr);
  37
  38         /*
  39          * We are called from hardware IRQs in case of callbacks.
  40          * But we can be called from softirq or process context in case
  41          * of submissions. In such case, we need to protect KM_IRQ0.
  42          */
  43         local_irq_save(flags);
  44         map = kmap_atomic(pg, KM_IRQ0);
  45         ptr = map + (dma_addr & (PAGE_SIZE-1));
  46         memcpy(dst, ptr, len);
  47         kunmap_atomic(map, KM_IRQ0);
  48         local_irq_restore(flags);
  49         return 0;
  50 }
  51 #endif /* __i386__ */
  52
  53 #ifndef MON_HAS_UNMAP
  54 char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len)
  55 {
  56         return 'D';
  57 }
  58 #endif