From patchwork Tue May 26 21:06:34 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robert Jarzmik X-Patchwork-Id: 6485991 Return-Path: X-Original-To: patchwork-dmaengine@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id AE9D9C0020 for ; Tue, 26 May 2015 21:08:08 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id AA2C320445 for ; Tue, 26 May 2015 21:08:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9796D203FB for ; Tue, 26 May 2015 21:08:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751793AbbEZVIF (ORCPT ); Tue, 26 May 2015 17:08:05 -0400 Received: from smtp01.smtpout.orange.fr ([80.12.242.123]:39855 "EHLO smtp.smtpout.orange.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751545AbbEZVIE (ORCPT ); Tue, 26 May 2015 17:08:04 -0400 Received: from belgarion.home ([109.222.71.104]) by mwinf5d02 with ME id Yl7z1q0032EzjTh03l829c; Tue, 26 May 2015 23:08:03 +0200 X-ME-Helo: belgarion.home X-ME-Date: Tue, 26 May 2015 23:08:03 +0200 X-ME-IP: 109.222.71.104 From: Robert Jarzmik To: Vinod Koul , Jonathan Corbet Cc: dmaengine@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Robert Jarzmik , Maxime Ripard Subject: [PATCH RESEND 2/2] Documentation: dmaengine: document DMA_CTRL_ACK Date: Tue, 26 May 2015 23:06:34 +0200 Message-Id: <1432674394-32007-3-git-send-email-robert.jarzmik@free.fr> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1432674394-32007-1-git-send-email-robert.jarzmik@free.fr> References: <1432674394-32007-1-git-send-email-robert.jarzmik@free.fr> Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM, RCVD_IN_DNSWL_HI,T_RP_MATCHES_RCVD,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add documentation about acking the transfers, and their reusability. Signed-off-by: Robert Jarzmik Cc: Maxime Ripard Acked-by: Maxime Ripard --- 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 --------------------