X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=Documentation%2FDMA-mapping.txt;h=d84f89dbf921401ac0e7afbe2d291b4dc304ef97;hb=f230d3f53d72d05bcb5666ab7e2eccd49c8b3a15;hp=e07f2530326b3afcbe69e77720833435e75e57d7;hpb=0d090b6819e3559dabb05773c4a6dacc4fa94d0e;p=linux-2.6-omap-h63xx.git diff --git a/Documentation/DMA-mapping.txt b/Documentation/DMA-mapping.txt index e07f2530326..d84f89dbf92 100644 --- a/Documentation/DMA-mapping.txt +++ b/Documentation/DMA-mapping.txt @@ -189,12 +189,6 @@ smaller mask as pci_set_dma_mask(). However for the rare case that a device driver only uses consistent allocations, one would have to check the return value from pci_set_consistent_dma_mask(). -If your 64-bit device is going to be an enormous consumer of DMA -mappings, this can be problematic since the DMA mappings are a -finite resource on many platforms. Please see the "DAC Addressing -for Address Space Hungry Devices" section near the end of this -document for how to handle this case. - Finally, if your device can only drive the low 24-bits of address during PCI bus mastering you might do something like: @@ -203,8 +197,6 @@ address during PCI bus mastering you might do something like: "mydev: 24-bit DMA addressing not available.\n"); goto ignore_this_device; } -[Better use DMA_24BIT_MASK instead of 0x00ffffff. -See linux/include/dma-mapping.h for reference.] When pci_set_dma_mask() is successful, and returns zero, the PCI layer saves away this mask you have provided. The PCI layer will use this @@ -514,7 +506,7 @@ With scatterlists, you map a region gathered from several regions by: int i, count = pci_map_sg(dev, sglist, nents, direction); struct scatterlist *sg; - for (i = 0, sg = sglist; i < count; i++, sg++) { + for_each_sg(sglist, sg, count, i) { hw_address[i] = sg_dma_address(sg); hw_len[i] = sg_dma_len(sg); } @@ -652,18 +644,6 @@ It is planned to completely remove virt_to_bus() and bus_to_virt() as they are entirely deprecated. Some ports already do not provide these as it is impossible to correctly support them. - 64-bit DMA and DAC cycle support - -Do you understand all of the text above? Great, then you already -know how to use 64-bit DMA addressing under Linux. Simply make -the appropriate pci_set_dma_mask() calls based upon your cards -capabilities, then use the mapping APIs above. - -It is that simple. - -Well, not for some odd devices. See the next section for information -about that. - Optimizing Unmap State Space Consumption On many platforms, pci_unmap_{single,page}() is simply a nop. @@ -782,5 +762,5 @@ following people: Jay Estabrook Thomas Sailer Andrea Arcangeli - Jens Axboe + Jens Axboe David Mosberger-Tang