diff options
Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/dma-api-howto.rst | 24 | ||||
| -rw-r--r-- | Documentation/core-api/entry.rst | 2 | ||||
| -rw-r--r-- | Documentation/core-api/printk-index.rst | 4 |
3 files changed, 25 insertions, 5 deletions
diff --git a/Documentation/core-api/dma-api-howto.rst b/Documentation/core-api/dma-api-howto.rst index e8a55f9d61db..0bf31b6c4383 100644 --- a/Documentation/core-api/dma-api-howto.rst +++ b/Documentation/core-api/dma-api-howto.rst @@ -203,13 +203,33 @@ setting the DMA mask fails. In this manner, if a user of your driver reports that performance is bad or that the device is not even detected, you can ask them for the kernel messages to find out exactly why. -The standard 64-bit addressing device would do something like this:: +The 24-bit addressing device would do something like this:: - if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64))) { + if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(24))) { dev_warn(dev, "mydev: No suitable DMA available\n"); goto ignore_this_device; } +The standard 64-bit addressing device would do something like this:: + + dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)) + +dma_set_mask_and_coherent() never return fail when DMA_BIT_MASK(64). Typical +error code like:: + + /* Wrong code */ + if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64))) + dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)) + +dma_set_mask_and_coherent() will never return failure when bigger than 32. +So typical code like:: + + /* Recommended code */ + if (support_64bit) + dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); + else + dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)); + If the device only supports 32-bit addressing for descriptors in the coherent allocations, but supports full 64-bits for streaming mappings it would look like this:: diff --git a/Documentation/core-api/entry.rst b/Documentation/core-api/entry.rst index e12f22ab33c7..a15f9b1767a2 100644 --- a/Documentation/core-api/entry.rst +++ b/Documentation/core-api/entry.rst @@ -18,7 +18,7 @@ exceptions`_, `NMI and NMI-like exceptions`_. Non-instrumentable code - noinstr --------------------------------- -Most instrumentation facilities depend on RCU, so intrumentation is prohibited +Most instrumentation facilities depend on RCU, so instrumentation is prohibited for entry code before RCU starts watching and exit code after RCU stops watching. In addition, many architectures must save and restore register state, which means that (for example) a breakpoint in the breakpoint entry code would diff --git a/Documentation/core-api/printk-index.rst b/Documentation/core-api/printk-index.rst index 3062f37d119b..1979c5dd32fe 100644 --- a/Documentation/core-api/printk-index.rst +++ b/Documentation/core-api/printk-index.rst @@ -4,7 +4,7 @@ Printk Index ============ -There are many ways how to monitor the state of the system. One important +There are many ways to monitor the state of the system. One important source of information is the system log. It provides a lot of information, including more or less important warnings and error messages. @@ -101,7 +101,7 @@ their own wrappers adding __printk_index_emit(). Only few subsystem specific wrappers have been updated so far, for example, dev_printk(). As a result, the printk formats from -some subsystes can be missing in the printk index. +some subsystems can be missing in the printk index. Subsystem specific prefix |