Merge remote-tracking branch 'iommu/next'

[karo-tx-linux.git] / Documentation / DMA-API-HOWTO.txt

diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt
index 14129f149a75432589f3bc925f7776a59354ef62..5e983031cc11be35fba1aab90546db5a7de1eeb3 100644 (file)
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -101,14 +101,23 @@ style to do this even if your device holds the default setting,
 because this shows that you did think about these issues wrt. your
 device.
 
 because this shows that you did think about these issues wrt. your
 device.
 

-The query is performed via a call to dma_set_mask():
+The query is performed via a call to dma_set_mask_and_coherent():

 
 

-       int dma_set_mask(struct device *dev, u64 mask);
+       int dma_set_mask_and_coherent(struct device *dev, u64 mask);

 
 

-The query for consistent allocations is performed via a call to
-dma_set_coherent_mask():
+which will query the mask for both streaming and coherent APIs together.
+If you have some special requirements, then the following two separate
+queries can be used instead:

 
 

-       int dma_set_coherent_mask(struct device *dev, u64 mask);
+       The query for streaming mappings is performed via a call to
+       dma_set_mask():
+
+               int dma_set_mask(struct device *dev, u64 mask);
+
+       The query for consistent allocations is performed via a call
+       to dma_set_coherent_mask():
+
+               int dma_set_coherent_mask(struct device *dev, u64 mask);

 
 Here, dev is a pointer to the device struct of your device, and mask
 is a bit mask describing which bits of an address your device
 
 Here, dev is a pointer to the device struct of your device, and mask
 is a bit mask describing which bits of an address your device


@@ -137,7 +146,7 @@ exactly why.
 
 The standard 32-bit addressing device would do something like this:
 
 
 The standard 32-bit addressing device would do something like this:
 

-       if (dma_set_mask(dev, DMA_BIT_MASK(32))) {
+       if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32))) {

                printk(KERN_WARNING
                       "mydev: No suitable DMA available.\n");
                goto ignore_this_device;
                printk(KERN_WARNING
                       "mydev: No suitable DMA available.\n");
                goto ignore_this_device;


@@ -171,22 +180,20 @@ the case would look like this:
 
        int using_dac, consistent_using_dac;
 
 
        int using_dac, consistent_using_dac;
 

-       if (!dma_set_mask(dev, DMA_BIT_MASK(64))) {
+       if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64))) {

                using_dac = 1;
                consistent_using_dac = 1;
                using_dac = 1;
                consistent_using_dac = 1;

-               dma_set_coherent_mask(dev, DMA_BIT_MASK(64));
-       } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) {
+       } else if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32))) {

                using_dac = 0;
                consistent_using_dac = 0;
                using_dac = 0;
                consistent_using_dac = 0;

-               dma_set_coherent_mask(dev, DMA_BIT_MASK(32));

        } else {
                printk(KERN_WARNING
                       "mydev: No suitable DMA available.\n");
                goto ignore_this_device;
        }
 
        } else {
                printk(KERN_WARNING
                       "mydev: No suitable DMA available.\n");
                goto ignore_this_device;
        }
 

-dma_set_coherent_mask() will always be able to set the same or a
-smaller mask as dma_set_mask(). However for the rare case that a
+The coherent coherent mask will always be able to set the same or a
+smaller mask as the streaming mask. However for the rare case that a

 device driver only uses consistent allocations, one would have to
 check the return value from dma_set_coherent_mask().
 
 device driver only uses consistent allocations, one would have to
 check the return value from dma_set_coherent_mask().
 


@@ -199,9 +206,9 @@ address you might do something like:
                goto ignore_this_device;
        }
 
                goto ignore_this_device;
        }
 

-When dma_set_mask() is successful, and returns zero, the kernel saves
-away this mask you have provided.  The kernel will use this
-information later when you make DMA mappings.
+When dma_set_mask() or dma_set_mask_and_coherent() is successful, and
+returns zero, the kernel saves away this mask you have provided.  The
+kernel will use this information later when you make DMA mappings.

 
 There is a case which we are aware of at this time, which is worth
 mentioning in this documentation.  If your device supports multiple
 
 There is a case which we are aware of at this time, which is worth
 mentioning in this documentation.  If your device supports multiple