From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: [PATCH 01/16] Blackfin SPI Driver: ensure cache coherency before doing DMA Date: Thu, 20 Nov 2008 14:05:06 -0800 Message-ID: <200811201405.06811.david-b@pacbell.net> References: <1226994760-4301-1-git-send-email-cooloney@kernel.org> <200811201347.46355.david-b@pacbell.net> <8bd0f97a0811201357g1ffeb7d3pfad6e178fb20050e@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Vitja Makarov , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Mike Frysinger" Return-path: In-Reply-To: <8bd0f97a0811201357g1ffeb7d3pfad6e178fb20050e-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org On Thursday 20 November 2008, Mike Frysinger wrote: > On Thu, Nov 20, 2008 at 16:47, David Brownell wrote: > > Basically, dma_map_single(), dma_unmap_single() ... and > > remember that the caller may have done the mappings for > > you already. > > these arent required to provide coherent memory right ? if that's the > case, i can take a look at getting things updated. Right. If caller provides dma-coherent memory to you, they must also have provided the DMA addresses the controller driver should be using ... so you won't need dma mapping calls on those paths. > > It'd be nice if one of patches snuck in a comment on that > > point: "Full duplex only works for non-DMA transfers." > > Same rationale: you may know this hardware inside out, > > but the next person won't. > > well, hopefully if they dont know they wont be touching the driver ;). > i'll add a comment in this code chunk. thanks for the feedback. The way it usually works is someone observes a problem and then starts experimenting on relevant code. So they learn a bit while debugging ... and code authors/maintainers need to keep that learning curve from being too steep. ;) - Dave ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/