[PATCH 1/2] Documentation: dmaengine: Add a description of what dmatest does

[Daniel Thompson <daniel.thompson@linaro.org>]

Currently it can difficult to determine what dmatest does without
reading the source code. Let's add a description.

The description is taken mostly from the patch header of
commit 4a776f0aa922 ("dmatest: Simple DMA memcpy test client")
although it has been edited and updated slightly.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
---
 Documentation/driver-api/dmaengine/dmatest.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/driver-api/dmaengine/dmatest.rst b/Documentation/driver-api/dmaengine/dmatest.rst
index ee268d445d38..529cc2cbbb1b 100644
--- a/Documentation/driver-api/dmaengine/dmatest.rst
+++ b/Documentation/driver-api/dmaengine/dmatest.rst
@@ -6,6 +6,16 @@ Andy Shevchenko <andriy.shevchenko@linux.intel.com>
 
 This small document introduces how to test DMA drivers using dmatest module.
 
+The dmatest module tests DMA memcpy, memset, XOR and RAID6 P+Q operations using
+various lengths and various offsets into the source and destination buffers. It
+will initialize both buffers with a repeatable pattern and verify that the DMA
+engine copies the requested region and nothing more. It will also verify that
+the bytes aren't swapped around, and that the source buffer isn't modified.
+
+The dmatest module can be configured to test a specific channel. It can also
+test multiple channels at the same time, and it can start multiple threads
+competing for the same channel.
+
 .. note::
   The test suite works only on the channels that have at least one
   capability of the following: DMA_MEMCPY (memory-to-memory), DMA_MEMSET
-- 
2.30.2