From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753169AbcHAXBH (ORCPT ); Mon, 1 Aug 2016 19:01:07 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:61761 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752938AbcHAXAq (ORCPT ); Mon, 1 Aug 2016 19:00:46 -0400 X-IBM-Helo: d24dlp02.br.ibm.com X-IBM-MailFrom: mauricfo@linux.vnet.ibm.com X-IBM-RcptTo: linux-doc@vger.kernel.org;linux-kernel@vger.kernel.org From: Mauricio Faria de Oliveira To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, corbet@lwn.net, akpm@linux-foundation.org, rmk+kernel@arm.linux.org.uk, keith.busch@intel.com, axboe@fb.com, benh@kernel.crashing.org, mpe@ellerman.id.au Cc: k.kozlowski@samsung.com Subject: [PATCH 1/3] dma-mapping: introduce the DMA_ATTR_NO_WARN attribute Date: Mon, 1 Aug 2016 19:59:48 -0300 X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1470092390-25451-1-git-send-email-mauricfo@linux.vnet.ibm.com> References: <1470092390-25451-1-git-send-email-mauricfo@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16080122-0020-0000-0000-0000022966E5 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16080122-0021-0000-0000-0000300F1996 Message-Id: <1470092390-25451-2-git-send-email-mauricfo@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-08-01_15:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1608010236 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce the DMA_ATTR_NO_WARN attribute, and document it. Signed-off-by: Mauricio Faria de Oliveira --- Documentation/DMA-attributes.txt | 17 +++++++++++++++++ include/linux/dma-mapping.h | 5 +++++ 2 files changed, 22 insertions(+) diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt index 2d455a5..98bf7ac 100644 --- a/Documentation/DMA-attributes.txt +++ b/Documentation/DMA-attributes.txt @@ -126,3 +126,20 @@ means that we won't try quite as hard to get them. NOTE: At the moment DMA_ATTR_ALLOC_SINGLE_PAGES is only implemented on ARM, though ARM64 patches will likely be posted soon. + +DMA_ATTR_NO_WARN +---------------- + +This tells the DMA-mapping subsystem to suppress allocation failure reports +(similarly to __GFP_NOWARN). + +On some architectures allocation failures are reported with error messages +to the system logs. Although this can help to identify and debug problems, +drivers which handle failures (eg, retry later) have no problems with them, +and can actually flood the system logs with error messages that aren't any +problem at all, depending on the implementation of the retry mechanism. + +So, this provides a way for drivers to avoid those error messages on calls +where allocation failures are not a problem, and shouldn't bother the logs. + +NOTE: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC. diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 66533e1..6efbd27 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -56,6 +56,11 @@ * that gives better TLB efficiency. */ #define DMA_ATTR_ALLOC_SINGLE_PAGES (1UL << 7) +/* + * DMA_ATTR_NO_WARN: This tells the DMA-mapping subsystem to suppress + * allocation failure reports (similarly to __GFP_NOWARN). + */ +#define DMA_ATTR_NO_WARN (1UL << 8) /* * A dma_addr_t can hold any valid DMA or bus address for the platform. -- 1.8.3.1