Messages in this thread | | | Subject | Does pci_map_single magicly work on > 32 bit address for 32bit capable device? | From | Maxim Levitsky <> | Date | Fri, 11 Dec 2009 23:39:42 +0200 |
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Hi,
I am writing a driver, and I am faced with following problem:
I receive a kernel pointer, and I want device to dma into that memory. However, device is only capable of 32 bit dma.
I can create a 'consistent' mapping and use memcpy from/to it, but it feels like waste of performance.
According to Documentation/DMA-mapping.txt, I can tell that hw supports 32 bit dma using pci_set_dma_mask, however, what will happen if I pass arbitrary kernel address into pci_map_single. What will happen if the address is above 32 bit?
I tried to follow source of pci_map_single, but it is quite strongly buried. Also note that I don't need any scatter gather lists, because buffer will always be 512 bytes long.
Note that I don't write the block driver itself, but a small driver that plugs into that driver. I am writing a driver for mtd subsystem and more precisely a nand driver.
Unfortunately mtd system can call the driver with arbitrary kernel pointer, although I am sure its not vmalloc'ed. Usually it passes the pointer that is received from block subsystem.
Thanks in advance, Maxim Levitsky
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