From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from VA3EHSOBE006.bigfish.com (va3ehsobe006.messaging.microsoft.com [216.32.180.16]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "Cybertrust SureServer Standard Validation CA" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 3982CB7109 for ; Sat, 5 Feb 2011 13:05:03 +1100 (EST) From: Tabi Timur-B04825 To: Dan Malek Subject: Re: minimum guaranteed alignment of dma_alloc_coherent? Date: Sat, 5 Feb 2011 02:04:40 +0000 Message-ID: <4D4CB038.9020602@freescale.com> References: <2A5A3DDA-94B3-48E3-9E49-6A5260BE1484@digitaldans.com> In-Reply-To: <2A5A3DDA-94B3-48E3-9E49-6A5260BE1484@digitaldans.com> Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 Cc: "linuxppc-dev@lists.ozlabs.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Dan Malek wrote: > > >> On a side note, do I really need to pass GFP_DMA .... > > The GFP_DMA is architecture dependent. Are you writing > a driver to be used across multiple architectures? It's conceivable that the driver could work on PowerPC and ARM. > If it's > necessary, I'd document why you are using it (an ISA device > on x86 for example) and then let other architectures > determine if it's necessary for them. I guess I'm not clear. I was wondering why an API called "dma_alloc_cohere= nt" (that has the word "dma" in it) needs to be told to allocate DMA-safe m= emory. When would it make sense to call dma_alloc_cohernet without GFP_DMA= ? If you don't want DMA-able memory, then you shouldn't be calling dma_all= oc_anything. --=20 Timur Tabi Linux kernel developer=