linux-kernel - [PATCH RESEND 2/2] Documentation: dmaengine: document DMA_CTRL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1432674394-32007-3-git-send-email-robert.jarzmik@free.fr>
Date:	Tue, 26 May 2015 23:06:34 +0200
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Vinod Koul <vinod.koul@...el.com>, Jonathan Corbet <corbet@....net>
Cc:	dmaengine@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: [PATCH RESEND 2/2] Documentation: dmaengine: document DMA_CTRL_ACK

Add documentation about acking the transfers, and their
reusability.

Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>
Cc: Maxime Ripard <maxime.ripard@...e-electrons.com>
---
 Documentation/dmaengine/provider.txt | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/Documentation/dmaengine/provider.txt b/Documentation/dmaengine/provider.txt
index 05d2280..ca67b0f 100644
--- a/Documentation/dmaengine/provider.txt
+++ b/Documentation/dmaengine/provider.txt
@@ -345,11 +345,12 @@ where to put them)
       that abstracts it away.
 
   * DMA_CTRL_ACK
-    - Undocumented feature
-    - No one really has an idea of what it's about, besides being
-      related to reusing the DMA transaction descriptors or having
-      additional transactions added to it in the async-tx API
-    - Useless in the case of the slave API
+    - If set, the transfer can be reused after being completed.
+    - There is a guarantee the transfer won't be freed until it is acked
+      by async_tx_ack().
+    - As a consequence, if a device driver wants to skip the dma_map_sg() and
+      dma_unmap_sg() in between 2 transfers, because the DMA'd data wasn't used,
+      it can resubmit the transfer right after its completion.
 
 General Design Notes
 --------------------
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/