Hi, The report of Jonathan Corbet from the Kernel Summit at [1] contains the following sentences, without details: « The venerable DMA memory zone will go away, replaced by a more flexible way of allocating memory which meets specific requirements. » What's exactly going to be done ? I'm interested by this issue, because I faced some limitations with the DMA memory zone thing back in 2004, that I reported on the linux-kernel and linux-mips mailing lists [2]. To sum up the issue: I was porting the 2.6 linux kernel on a board with a somewhat curious memory configuration. It had 256 Mb of RAM attached to the processor memory controller, and another 128 Mb of RAM attached to a Marvell chipset. The physical memory layout seen by the operating system running was fixed : it saw the 256 Mb from addresses 0 to 256 Mb, and then the 128 Mb from addresses 256 to 384 Mb. The Marvell chipset, amongst others, contained a Ethernet controller, and if you wanted to DMA from/to it, you had to put the data in the 128 Mb of RAM attached to the the chipset. I was never able to find a solution that would allow the SKB to be directly allocated from that 128 Mb region, and only from that region, so that they could be directly DMA-able by the chipset. So I went with an ugly solution: managing by hand those 128 Mb, and copying back-and-forth the SKB between the 256 Mb and 128 Mb memories upon transmission and reception of packets. Ugly. So, when I saw that a more flexible way of allocating memory was in the works, I immediatly wonder if it could solve the aforementionned issue. Thanks! Thomas [1] http://lwn.net/Articles/248343/ [2] http://lkml.org/lkml/2004/9/28/36 -- PETAZZONI Thomas - thomas.petazzoni@xxxxxxxx http://{thomas,sos,kos}.enix.org - Jabber: thomas.petazzoni@xxxxxxxxx http://{agenda,livret}dulibre.org - http://www.toulibre.org Fingerprint : 0BE1 4CF3 CEA4 AC9D CC6E 1624 F653 CB30 98D3 F7A7
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