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authorDan Williams <dan.j.williams@intel.com>2009-07-14 12:20:36 -0700
committerDan Williams <dan.j.williams@intel.com>2009-08-29 19:09:27 -0700
commitb2f46fd8ef3dff2ab30f31126833f78b7480283a (patch)
tree9f111e3e313b4d142c12d2d8156a2704a36904f8 /Documentation/crypto
parent95475e57113c66aac7583925736ed2e2d58c990d (diff)
downloadlinux-linaro-android-b2f46fd8ef3dff2ab30f31126833f78b7480283a.tar.gz
async_tx: add support for asynchronous GF multiplication
[ Based on an original patch by Yuri Tikhonov ] This adds support for doing asynchronous GF multiplication by adding two additional functions to the async_tx API: async_gen_syndrome() does simultaneous XOR and Galois field multiplication of sources. async_syndrome_val() validates the given source buffers against known P and Q values. When a request is made to run async_pq against more than the hardware maximum number of supported sources we need to reuse the previous generated P and Q values as sources into the next operation. Care must be taken to remove Q from P' and P from Q'. For example to perform a 5 source pq op with hardware that only supports 4 sources at a time the following approach is taken: p, q = PQ(src0, src1, src2, src3, COEF({01}, {02}, {04}, {08})) p', q' = PQ(p, q, q, src4, COEF({00}, {01}, {00}, {10})) p' = p + q + q + src4 = p + src4 q' = {00}*p + {01}*q + {00}*q + {10}*src4 = q + {10}*src4 Note: 4 is the minimum acceptable maxpq otherwise we punt to synchronous-software path. The DMA_PREP_CONTINUE flag indicates to the driver to reuse p and q as sources (in the above manner) and fill the remaining slots up to maxpq with the new sources/coefficients. Note1: Some devices have native support for P+Q continuation and can skip this extra work. Devices with this capability can advertise it with dma_set_maxpq. It is up to each driver how to handle the DMA_PREP_CONTINUE flag. Note2: The api supports disabling the generation of P when generating Q, this is ignored by the synchronous path but is implemented by some dma devices to save unnecessary writes. In this case the continuation algorithm is simplified to only reuse Q as a source. Cc: H. Peter Anvin <hpa@zytor.com> Cc: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: Yuri Tikhonov <yur@emcraft.com> Signed-off-by: Ilya Yanok <yanok@emcraft.com> Reviewed-by: Andre Noll <maan@systemlinux.org> Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'Documentation/crypto')
-rw-r--r--Documentation/crypto/async-tx-api.txt3
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/crypto/async-tx-api.txt b/Documentation/crypto/async-tx-api.txt
index 6b15e488c0e..0e48e054d69 100644
--- a/Documentation/crypto/async-tx-api.txt
+++ b/Documentation/crypto/async-tx-api.txt
@@ -64,6 +64,9 @@ xor - xor a series of source buffers and write the result to a
xor_val - xor a series of source buffers and set a flag if the
result is zero. The implementation attempts to prevent
writes to memory
+pq - generate the p+q (raid6 syndrome) from a series of source buffers
+pq_val - validate that a p and or q buffer are in sync with a given series of
+ sources
3.3 Descriptor management:
The return value is non-NULL and points to a 'descriptor' when the operation