Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759530Ab1FQSJy (ORCPT ); Fri, 17 Jun 2011 14:09:54 -0400 Received: from mail-qy0-f174.google.com ([209.85.216.174]:55418 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752353Ab1FQSJx convert rfc822-to-8bit (ORCPT ); Fri, 17 Jun 2011 14:09:53 -0400 MIME-Version: 1.0 In-Reply-To: <20110617124035.GA19693@parisc-linux.org> References: <1308227453-2034-1-git-send-email-shawn.guo@linaro.org> <20110617124035.GA19693@parisc-linux.org> Date: Fri, 17 Jun 2011 20:09:44 +0200 Message-ID: Subject: Re: [PATCH v3 RESEND] dma-mapping: add new API for max_segment_number From: Per Forlin To: Matthew Wilcox Cc: Shawn Guo , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Russell King - ARM Linux , vinod.koul@intel.com, gregkh@suse.de, FUJITA Tomonori , Dan Williams , cjb@laptop.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1569 Lines: 32 On 17 June 2011 14:40, Matthew Wilcox wrote: > On Thu, Jun 16, 2011 at 08:30:53PM +0800, Shawn Guo wrote: >> Here is the user story that tells the need of the new api. ?The >> mxs-mmc is the mmc host controller for Freescale MXS architecture. >> There are a pair of ?mmc host specific parameters max_seg_size and >> max_segs that mxs-mmc host driver needs to tell mmc core, so that >> mmc core can know how big each data segment could be and how many >> segments could be handled one time in a scatter list by host driver. >> >> The mxs-mmc driver is one user of dmaengine mxs-dma, and it will call >> mxs-dma to transfer data in scatter list. ?That is to say mxs-mmc has >> no idea of what max_seg_size and max_segs should be, because they are >> all mxs-dma capability parameters, and mxs-mmc needs to query them >> from mxs-dma. > > This approach would make sense if mxs-mmc were generic, but it's tied to > mxs-dma, so it can just as well call mxs-dma to find out how many segments > it supports. > mxs-dma use the generic dmaengine.h. The patch is not only intended for mxs-mmc. MMCI and other mmc host drivers need a way to query max_seg_number. It would be possible to store this number within drivers/dmaengine but this would not work for omap_hsmmc that doesn't use drivers/dmaengine Regards, Per -- 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/