Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756382Ab1FTXpR (ORCPT ); Mon, 20 Jun 2011 19:45:17 -0400 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:33154 "EHLO opensource2.wolfsonmicro.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756218Ab1FTXpP (ORCPT ); Mon, 20 Jun 2011 19:45:15 -0400 Date: Tue, 21 Jun 2011 00:45:13 +0100 From: Mark Brown To: Lars-Peter Clausen Cc: linux-kernel@vger.kernel.org, Dimitris Papastamos , Liam Girdwood , Samuel Oritz , Graeme Gregory Subject: Re: [PATCH 3/8] regmap: Add SPI bus support Message-ID: <20110620234513.GC1905@opensource.wolfsonmicro.com> References: <20110620124608.GB31140@opensource.wolfsonmicro.com> <1308574489-31322-1-git-send-email-broonie@opensource.wolfsonmicro.com> <1308574489-31322-3-git-send-email-broonie@opensource.wolfsonmicro.com> <4DFFD738.4090206@metafoo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DFFD738.4090206@metafoo.de> X-Cookie: You are magnetic in your bearing. User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1227 Lines: 26 On Tue, Jun 21, 2011 at 01:26:48AM +0200, Lars-Peter Clausen wrote: > On 06/20/2011 02:54 PM, Mark Brown wrote: > > +static int regmap_spi_read(struct device *dev, > > + const void *reg, size_t reg_size, > > + void *val, size_t val_size) > > +{ > > + struct spi_device *spi = to_spi_device(dev); > > + return spi_write_then_read(spi, reg, reg_size, val, val_size); > spi_write_then_read will use a bounce buffer internally, since we already have > our own bounce buffer it is probably better to use the low-level spi interface > directly in this case. I've got this horrible feeling that if we try that we'll discover that the reason the SPI API does this internally is just as valid here - if I remember correctly it's doing this due to restrictions on DMA from the stack and I'd strongly expect val to end up on the stack for registers. Or to look at it from the other point of view if we don't need the bounce buffers then why does spi_write_then_read() need them? -- 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/