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Dear Dave,<BR>
<BR>
Thanks for your answer first. However I am very confused. It seems that I understand the memory-mapping-related functions completely wrong. Here comes more questions. <BR><BR><BR>> The address you are passing to mmap is where the pointer will be mapped<BR>> in virtual address space. You need to determine the DMA memory address<BR>> page number down in the actual mmap call.<BR>> <BR>> int foo_mmap(struct file* filep, struct vm_area_struct* vma)<BR>> {<BR>> unsigned long dma_addr = 0x03000000;<BR>> unsigned long dma_size = 0x00200000;<BR>> unsigned long pfn;<BR>> <BR>> // convert the DMA address to page number<BR>> pfn = virt_to_phys(dma_addr) >> PAGE_SHIFT;<BR><BR>
Shall I use virt_to_phys? dma_addr is already exactly physical address which is used to initiate DMA transfers. <BR>
<BR>
> // remap our page frame to the vma offset<BR>> remap_pfn_range(vma, vma->vm_start, pfn, <BR>> dma_size, vma->vm_page_prot);<BR>> }<BR>> <BR>> Change the address parameter from 0x03000000 to 0:<BR>> <BR>> lut_mem_base = (unsigned int *) mmap(0, LUT_SIZE_IN_BYTE, <BR>> PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);<BR><BR>
Previously I used "remap_page_range(vma, vma->vm_start, physical_addr, vm_size, vma->vm_page_prot)" in the device driver, where physical_addr is 0x03000000. In the application program, I used "lut_mem_base = (unsigned int *) mmap(0, LUT_SIZE_IN_BYTE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);". I think it is correct but it doesn't work. I heard that in the new kernels, remap_page_range is not supported any more. However when I compile the driver, nothing was shown to complain that. I am using 2.6.10 kernel. Any hint for this?<BR>
<BR>
Thank you for your help to make me understand. <BR>
<BR>
BR<BR>
Ming<BR><br /><hr />使用新一代 Windows Live Messenger 轻松交流和共享！ <a href='http://messenger.live.cn/' target='_new'>立即体验！</a></body>
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