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r: 199158
b: refs/heads/master
c: 2f20ccf
h: refs/heads/master
v: v3
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Tejun Heo authored and Jeff Garzik committed May 25, 2010
1 parent 6b1d2d5 commit 9a328dd
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2 changes: 1 addition & 1 deletion [refs]
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---
refs/heads/master: 9dda696f0de87a2e5cfabb147e28c76b7d3c6846
refs/heads/master: 2f20ccf8190b064468cb2c7ba92e757ae37e61b1
15 changes: 0 additions & 15 deletions trunk/Documentation/ABI/testing/sysfs-firmware-sfi

This file was deleted.

85 changes: 36 additions & 49 deletions trunk/Documentation/DMA-API-HOWTO.txt
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Expand Up @@ -639,36 +639,6 @@ 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.

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.
Expand Down Expand Up @@ -733,25 +703,42 @@ to "Closing".

1) Struct scatterlist requirements.

Don't invent the architecture specific struct scatterlist; just use
<asm-generic/scatterlist.h>. You need to enable
CONFIG_NEED_SG_DMA_LENGTH if the architecture supports IOMMUs
(including software IOMMU).

2) ARCH_KMALLOC_MINALIGN

Architectures must ensure that kmalloc'ed buffer is
DMA-safe. Drivers and subsystems depend on it. If an architecture
isn't fully DMA-coherent (i.e. hardware doesn't ensure that data in
the CPU cache is identical to data in main memory),
ARCH_KMALLOC_MINALIGN must be set so that the memory allocator
makes sure that kmalloc'ed buffer doesn't share a cache line with
the others. See arch/arm/include/asm/cache.h as an example.

Note that ARCH_KMALLOC_MINALIGN is about DMA memory alignment
constraints. You don't need to worry about the architecture data
alignment constraints (e.g. the alignment constraints about 64-bit
objects).
Struct scatterlist must contain, at a minimum, the following
members:

struct page *page;
unsigned int offset;
unsigned int length;

The base address is specified by a "page+offset" pair.

Previous versions of struct scatterlist contained a "void *address"
field that was sometimes used instead of page+offset. As of Linux
2.5., page+offset is always used, and the "address" field has been
deleted.

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.
*/
}

Closing

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5 changes: 0 additions & 5 deletions trunk/Documentation/SubmittingDrivers
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Expand Up @@ -130,8 +130,6 @@ Linux kernel master tree:
ftp.??.kernel.org:/pub/linux/kernel/...
?? == your country code, such as "us", "uk", "fr", etc.

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git

Linux kernel mailing list:
linux-kernel@vger.kernel.org
[mail majordomo@vger.kernel.org to subscribe]
Expand Down Expand Up @@ -162,6 +160,3 @@ How to NOT write kernel driver by Arjan van de Ven:

Kernel Janitor:
http://janitor.kernelnewbies.org/

GIT, Fast Version Control System:
http://git-scm.com/
2 changes: 1 addition & 1 deletion trunk/Documentation/cgroups/cgroups.txt
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Expand Up @@ -339,7 +339,7 @@ To mount a cgroup hierarchy with all available subsystems, type:
The "xxx" is not interpreted by the cgroup code, but will appear in
/proc/mounts so may be any useful identifying string that you like.

To mount a cgroup hierarchy with just the cpuset and memory
To mount a cgroup hierarchy with just the cpuset and numtasks
subsystems, type:
# mount -t cgroup -o cpuset,memory hier1 /dev/cgroup

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