From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sinan Kaya Subject: Re: [PATCH V3 3/4] dmaselftest: add memcpy selftest support functions Date: Mon, 9 Nov 2015 23:49:54 -0500 Message-ID: <56417772.7050905@codeaurora.org> References: <1446958380-23298-1-git-send-email-okaya@codeaurora.org> <1446958380-23298-4-git-send-email-okaya@codeaurora.org> <563EDA15.7070606@codeaurora.org> <56400909.2090300@codeaurora.org> <5640A429.6090302@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.codeaurora.org ([198.145.29.96]:56047 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751033AbbKJEt7 (ORCPT ); Mon, 9 Nov 2015 23:49:59 -0500 In-Reply-To: <5640A429.6090302@codeaurora.org> Sender: linux-arm-msm-owner@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org To: Timur Tabi , dmaengine@vger.kernel.org, cov@codeaurora.org, jcm@redhat.com Cc: agross@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Vinod Koul , Dan Williams , linux-kernel@vger.kernel.org On 11/9/2015 8:48 AM, Timur Tabi wrote: > Sinan Kaya wrote: >>> >>> And why kmalloc anyway? Why not leave it on the stack? >>> >>> char src[] = "hello world"; >>> >>> ? >> >> I need to call dma_map_single on this address to convert it to a DMA >> address. That's why. > > And you can't do that with an object that's on the stack? > no, pasting from here. https://www.kernel.org/doc/Documentation/DMA-API-HOWTO.txt under 'What memory is DMA'able?' This rule also means that you may use neither kernel image addresses (items in data/text/bss segments), nor module image addresses, nor stack addresses for DMA. -- Sinan Kaya Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project