The patch titled
Documentation: move the error handling to the better place in DMA-API-HOWTO
has been added to the -mm tree. Its filename is
documentation-move-the-error-handling-to-the-better-place-in-dma-api-howto.patch
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Subject: Documentation: move the error handling to the better place in DMA-API-HOWTO
From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Handing DMA mapping errors is essential. Let's put it in the more
appropriate place rather than the end of the doc.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/DMA-API-HOWTO.txt | 60 +++++++++++++++---------------
1 file changed, 30 insertions(+), 30 deletions(-)
diff -puN Documentation/DMA-API-HOWTO.txt~documentation-move-the-error-handling-to-the-better-place-in-dma-api-howto Documentation/DMA-API-HOWTO.txt
--- a/Documentation/DMA-API-HOWTO.txt~documentation-move-the-error-handling-to-the-better-place-in-dma-api-howto
+++ a/Documentation/DMA-API-HOWTO.txt
@@ -639,6 +639,36 @@ is planned to completely remove virt_to_
they are entirely deprecated. Some ports already do not provide these
as it is impossible to correctly support them.
+ Handling Errors
+
+DMA address space is limited on some architectures and an allocation
+failure can be determined by:
+
+- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0
+
+- checking the returned dma_addr_t of dma_map_single and dma_map_page
+ by using dma_mapping_error():
+
+ dma_addr_t dma_handle;
+
+ dma_handle = dma_map_single(dev, addr, size, direction);
+ if (dma_mapping_error(dev, dma_handle)) {
+ /*
+ * reduce current DMA mapping usage,
+ * delay and try again later or
+ * reset driver.
+ */
+ }
+
+Networking drivers must call dev_kfree_skb to free the socket buffer
+and return NETDEV_TX_OK if the DMA mapping fails on the transmit hook
+(ndo_start_xmit). This means that the socket buffer is just dropped in
+the failure case.
+
+SCSI drivers must return SCSI_MLQUEUE_HOST_BUSY if the DMA mapping
+fails in the queuecommand hook. This means that the SCSI subsystem
+passes the command to the driver again later.
+
Optimizing Unmap State Space Consumption
On many platforms, dma_unmap_{single,page}() is simply a nop.
@@ -710,36 +740,6 @@ to "Closing".
2) More to come...
- Handling Errors
-
-DMA address space is limited on some architectures and an allocation
-failure can be determined by:
-
-- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0
-
-- checking the returned dma_addr_t of dma_map_single and dma_map_page
- by using dma_mapping_error():
-
- dma_addr_t dma_handle;
-
- dma_handle = dma_map_single(dev, addr, size, direction);
- if (dma_mapping_error(dev, dma_handle)) {
- /*
- * reduce current DMA mapping usage,
- * delay and try again later or
- * reset driver.
- */
- }
-
-Networking drivers must call dev_kfree_skb to free the socket buffer
-and return NETDEV_TX_OK if the DMA mapping fails on the transmit hook
-(ndo_start_xmit). This means that the socket buffer is just dropped in
-the failure case.
-
-SCSI drivers must return SCSI_MLQUEUE_HOST_BUSY if the DMA mapping
-fails in the queuecommand hook. This means that the SCSI subsystem
-passes the command to the driver again later.
-
Closing
This document, and the API itself, would not be in its current
_
Patches currently in -mm which might be from fujita.tomonori@xxxxxxxxxxxxx are
origin.patch
linux-next.patch
scsi-add-__init-__exit-macros-to-ibmvstgtc.patch
ia64-remove-unnecessary-sync_single_range_-in-swiotlb_dma_ops.patch
x86-remove-unnecessary-sync_single_range_-in-swiotlb_dma_ops.patch
powerpc-remove-unnecessary-sync_single_range_-in-swiotlb_dma_ops.patch
swiotlb-remove-unnecessary-swiotlb_sync_single_range_.patch
dma-mapping-remove-unnecessary-sync_single_range_-in-dma_map_ops.patch
documentation-add-networking-drivers-mapping-error-handling-to-dma-api-howto.patch
documentation-add-scsi-drivers-mapping-error-handling-to-dma-api-howto.patch
documentation-update-scatterlist-struct-description-in-dma-api-howto.patch
documentation-move-the-error-handling-to-the-better-place-in-dma-api-howto.patch
ssb-add-dma_dev-to-ssb_device-structure.patch
b43legacy-replace-the-ssb_dma-api-with-the-generic-dma-api.patch
b43-replace-the-ssb_dma-api-with-the-generic-dma-api.patch
b44-replace-the-ssb_dma-api-with-the-generic-dma-api.patch
ssb-remove-the-ssb-dma-api.patch
asm-generic-remove-isa_dma_threshold-in-scatterlisth.patch
asm-generic-add-need_sg_dma_length-to-define-sg_dma_len.patch
x86_32-use-asm-generic-scatterlisth.patch
powerpc-use-asm-generic-scatterlisth.patch
alpha-use-asm-generic-scatterlisth.patch
asm-generic-remove-arch_has_sg_chain-in-scatterlisth.patch
avr32-use-asm-generic-scatterlisth.patch
cris-use-asm-generic-scatterlisth.patch
h8300-use-asm-generic-scatterlisth.patch
m32r-use-use-asm-generic-scatterlisth.patch
m68k-use-asm-generic-scatterlisth.patch
mips-use-use-asm-generic-scatterlisth.patch
xtensa-use-use-asm-generic-scatterlisth.patch
blackfin-use-use-asm-generic-scatterlisth.patch
frv-use-asm-generic-scatterlisth.patch
mn10300-use-asm-generic-scatterlisth.patch
parisc-use-asm-generic-scatterlisth.patch
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