LddMemoryMapping < Training2

%SECTION0{name=LddMemoryMapping}% Memory mapping

   * allows userspace direct access to device memory

   * benefits:
      * avoids buffering: can improve performace
      * direct access to registers can avoid many =ioctl=

   * only makes sense in certain circumstances: e.g. _not_ for *stream*
     oriented devices

---++API: mmap

*file operation*

<verbatim>
int *mmap (struct file *filp, struct vm_area_struct *vma);
</verbatim>

*build page tables*

<verbatim>
int remap_pfn_range(struct vm_area_struct *vma, unsigned long virt_addr,
          unsigned long pfn, unsigned long size, pgprot_t prot);

/* identical to above on most plattforms: */
int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long virt_addr, 
             unsigned long phys_addr, unsigned long size, pgprot_t prot);

</verbatim>

5.3.7. =poll= and =select=		1. Denx Training Topics		5.4. Debugging Techniques
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