From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754238Ab2GSLa7 (ORCPT ); Thu, 19 Jul 2012 07:30:59 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:36740 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752677Ab2GSLaz (ORCPT ); Thu, 19 Jul 2012 07:30:55 -0400 Date: Thu, 19 Jul 2012 13:30:59 +0200 From: Daniel Vetter To: Rob Clark Cc: linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org Subject: Re: [Linaro-mm-sig] [PATCH] device: add dma_params->max_segment_count Message-ID: <20120719113059.GB5262@phenom.ffwll.local> Mail-Followup-To: Rob Clark , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org References: <1342115056-27419-1-git-send-email-rob.clark@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1342115056-27419-1-git-send-email-rob.clark@linaro.org> X-Operating-System: Linux phenom 3.4.0-rc3+ 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 On Thu, Jul 12, 2012 at 12:44:16PM -0500, Rob Clark wrote: > From: Rob Clark > > For devices which have constraints about maximum number of segments > in an sglist. For example, a device which could only deal with > contiguous buffers would set max_segment_count to 1. > > The initial motivation is for devices sharing buffers via dma-buf, > to allow the buffer exporter to know the constraints of other > devices which have attached to the buffer. The dma_mask and fields > in 'struct device_dma_parameters' tell the exporter everything else > that is needed, except whether the importer has constraints about > maximum number of segments. > > Signed-off-by: Rob Clark I like this and I guess it's an easy way to solve most of our sharing issues with funnier hw. Exporters can then fall back to large allocations, CMA, special-purpose remappes (like the omap tiler) or platform-specific carveout areas (stolen mem for drm/i915). One little thing though: Could you add a little helper (maybe in a second patch) to dma_buf that walks all currently attached buffers and ORs together all masks and takes the minimum of all other limits for all attached buffers? Yours, Daniel > --- > include/linux/device.h | 1 + > include/linux/dma-mapping.h | 16 ++++++++++++++++ > 2 files changed, 17 insertions(+) > > diff --git a/include/linux/device.h b/include/linux/device.h > index 161d962..3813735 100644 > --- a/include/linux/device.h > +++ b/include/linux/device.h > @@ -568,6 +568,7 @@ struct device_dma_parameters { > * sg limitations. > */ > unsigned int max_segment_size; > + unsigned int max_segment_count; /* zero for unlimited */ > unsigned long segment_boundary_mask; > }; > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index dfc099e..f380f79 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -111,6 +111,22 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev, > return -EIO; > } > > +static inline unsigned int dma_get_max_seg_count(struct device *dev) > +{ > + return dev->dma_parms ? dev->dma_parms->max_segment_count : 0; > +} > + > +static inline int dma_set_max_seg_count(struct device *dev, > + unsigned int count) > +{ > + if (dev->dma_parms) { > + dev->dma_parms->max_segment_count = count; > + return 0; > + } else > + return -EIO; > +} > + > + > static inline unsigned long dma_get_seg_boundary(struct device *dev) > { > return dev->dma_parms ? > -- > 1.7.9.5 > > > _______________________________________________ > Linaro-mm-sig mailing list > Linaro-mm-sig@lists.linaro.org > http://lists.linaro.org/mailman/listinfo/linaro-mm-sig -- Daniel Vetter Mail: daniel@ffwll.ch Mobile: +41 (0)79 365 57 48