Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753226AbaFDOMR (ORCPT ); Wed, 4 Jun 2014 10:12:17 -0400 Received: from 8bytes.org ([85.214.48.195]:50179 "EHLO mail.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751782AbaFDOMQ (ORCPT ); Wed, 4 Jun 2014 10:12:16 -0400 Date: Wed, 4 Jun 2014 16:12:11 +0200 From: Joerg Roedel To: Tejun Heo Cc: Shuah Khan , Eli Billauer , devel@driverdev.osuosl.org, gregkh@linuxfoundation.org, bhelgaas@google.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, iommu@lists.linux-foundation.org, discuss@x86-64.org Subject: Re: [PATCH v2 1/4] dma-mapping: Add devm_ interface for dma_map_single() Message-ID: <20140604141211.GC23880@8bytes.org> References: <1401606077-1739-1-git-send-email-eli.billauer@gmail.com> <1401606077-1739-2-git-send-email-eli.billauer@gmail.com> <538E3D04.9060808@samsung.com> <20140603233907.GB23880@8bytes.org> <20140604140408.GC5004@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140604140408.GC5004@htj.dyndns.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-DSPAM-Result: Whitelisted X-DSPAM-Processed: Wed Jun 4 16:12:13 2014 X-DSPAM-Confidence: 0.9995 X-DSPAM-Probability: 0.0000 X-DSPAM-Signature: 538f293d20863268771489 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 04, 2014 at 10:04:08AM -0400, Tejun Heo wrote: > Hmmm? Don't we have drivers which map dma buffers on device init and > release them on exit? For dynamic usages, its usefulness is limited > especially given that dynamic tracking of buffers usually would > involve tracking of other information too in addition to dma buffer > pointer themselves. If alloc on init and free on exit is a very rare > usage pattern, I have no objection against not adding devm interface > for dma mappings. Yes, but those drivers usually get DMA buffers at init time with the dma_alloc_* interfaces. The dma_map_* interfaces discussed here belong to the streaming DMA-API, so they are usually used for only one DMA transaction before dma_unmap_* is called on them. A devm interface for the dma_alloc_* family of functions would actually make sense, but not for the dma_map_* functions. Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/