From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [203.10.76.45]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx.ozlabs.org", Issuer "CA Cert Signing Authority" (verified OK)) by bilbo.ozlabs.org (Postfix) with ESMTPS id 9AA29B7B60 for ; Thu, 27 Aug 2009 06:21:12 +1000 (EST) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 052B4DDD01 for ; Thu, 27 Aug 2009 06:21:11 +1000 (EST) Message-Id: From: Becky Bruce To: michael@ellerman.id.au In-Reply-To: <1251295725.7492.5.camel@concordia> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Mime-Version: 1.0 (Apple Message framework v936) Subject: Re: [PATCH] powerpc: Change archdata dma_data type to dma_addr_t Date: Wed, 26 Aug 2009 15:20:56 -0500 References: <1251130634-15093-1-git-send-email-beckyb@kernel.crashing.org> <20090824194800.GA13503@lst.de> <1251289790.1379.71.camel@pasglop> <1251295725.7492.5.camel@concordia> Cc: Christoph Hellwig , linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Aug 26, 2009, at 9:08 AM, Michael Ellerman wrote: > On Wed, 2009-08-26 at 22:29 +1000, Benjamin Herrenschmidt wrote: >> On Mon, 2009-08-24 at 21:48 +0200, Christoph Hellwig wrote: >>> On Mon, Aug 24, 2009 at 11:17:14AM -0500, Becky Bruce wrote: >>>> Previously, this was specified as a void *, but that's not >>>> large enough on 32-bit systems with 36-bit physical >>>> addressing support. Change the type to dma_addr_t so it >>>> will scale based on the size of a dma address. >>> >>> This looks extreml ugly to me. It seems like the typical use is to >>> store a pointer to a structure. So what about making the direct >>> dma case follow that general scheme instead? >>> >>> E.g. declare a >>> >>> struct direct_dma_data { >>> dma_addr_t direct_dma_offset; >>> }; >>> >>> and have one normal instace of it, and one per weird cell device. >> >> Right, but we want to avoid a structure for the classic case of 32- >> bit >> systems with no iommu... >> >> I wouldn't mind doing a union here. > > That might be best, the patch as it stands is a horrible mess of > casts. Let's be fair - the code before was a horrible mess of casts, I've just moved them :) > > Stashing a dma_addr_t into a void * is sort of gross, but storing a > pointer to some struct (a void *) in a dma_addr_t is _really_ gross :) Both are revolting (and storing a dma_addr_t into a void * is really gross when the void * is smaller than the dma_addr_t!!). A union might not be a bad idea, though. I'll look at doing that instead. -Becky