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Date: Fri, 11 Dec 2009 23:39:42 +0200 From: Maxim Levitsky <maximlevitsky@...il.com> To: linux-kernel <linux-kernel@...r.kernel.org> Subject: Does pci_map_single magicly work on > 32 bit address for 32bit capable device? 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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