Hi, I am looking into a driver that works fine on 2.4, and trying to port it to 2.6. Allow me to explain the part of the driver that is relevant to my posting. The linux system has 512 MB. Through kernel command line (mem=448M), the kernel is using only 448 MB (setting aside 64 MB). The driver uses the 64 MB to do DMA to/from. Following is the assumption and technique it uses: 0x1c000000 = 448 MB = start address of 64 MB memory Size = 64 MB int * cpuAddr = ioremap ( 0x1c000000) Assuming the driver wants to DMA from offset 0x1000 of the 64MB memory, of size 0x400. Before doing DMA, it initializes varable of type scatterlist as follows: scatterlist.address = cpuAddr + 0x400 <---------- scatterlist.size = 0x400 scatterlist.dma_address = 0x1c000000 + 0x400 >From the above, I am guessing the code makes the assumption (and correctly so, as it works fine) that the starting DMA address of the 64 MB memory is 0x1c000000. Ofcourse the code assuemes that the 64MB is set aside in low memory. Please note that the above code is not my code, just code I am looking into. On 2.6, there is no more scatterlist.address. To port the driver to 2.6, I replaced the line above with the arrow as follows: scatterlist.page = virt_to_page(cpuAddr + 0x400) scatterlist.ofset = (cpuAddr + 0x400) & (~PAGE_MASK) And I am guessing the assumption of 0x1c000000 as the starting DMA address of the 64 MB is not right. When the the device that is trying to DMA from this address, it crashes. Can someone please help me with the following: 1. The device does not always fail when doing reads, but fails very soon after a few transactions? Any idea as to why the drivers evens works sometimes on 2.6. 2. How can I find out the DMA address of offset 0x1000 into the 64 MB memory? Should I use pci_map_single() ? If so, what do I pass it? 3. How can I properly initialize the scatterlist element? Thank you, Ahmed. __________________________________ Do you Yahoo!? All your favorites on one personal page ? Try My Yahoo! http://my.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
