From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vinod Koul Subject: Re: [PATCH v3 1/3] dmaengine: add dma_get_slave_sg_caps() Date: Tue, 12 Feb 2013 09:08:44 -0800 Message-ID: <20130212170844.GS3789@intel.com> References: <1360007224-21735-1-git-send-email-mporter@ti.com> <1360007224-21735-2-git-send-email-mporter@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mga11.intel.com ([192.55.52.93]:28879 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933329Ab3BLRdZ (ORCPT ); Tue, 12 Feb 2013 12:33:25 -0500 Content-Disposition: inline In-Reply-To: <1360007224-21735-2-git-send-email-mporter@ti.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Matt Porter Cc: Dan Williams , Chris Ball , Grant Likely , Linux DaVinci Kernel List , Linux Kernel Mailing List , Linux MMC List On Mon, Feb 04, 2013 at 02:47:02PM -0500, Matt Porter wrote: > Add a dmaengine API to retrieve slave SG transfer capabilities. > > The API is optionally implemented by dmaengine drivers and when > unimplemented will return a NULL pointer. A client driver using > this API provides the required dma channel, address width, and > burst size of the transfer. dma_get_slave_sg_caps() returns an > SG caps structure with the maximum number and size of SG segments > that the given channel can handle. Okay this sounds much better :-) few points though: - you added API for caps, but is actually calculating for given configuration the max allowed range. IMHO that is not caps, perhaps renaming to get_max_sg /some_better_name would be more apt. - Still I like the idea of caps, but it should give H/W support capablity. If you want to add that, pls develop on same line... -- ~Vinod > > Signed-off-by: Matt Porter > --- > include/linux/dmaengine.h | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h > index d3201e4..5b5b220 100644 > --- a/include/linux/dmaengine.h > +++ b/include/linux/dmaengine.h > @@ -371,6 +371,19 @@ struct dma_slave_config { > unsigned int slave_id; > }; > > +/* struct dma_slave_sg_caps - expose SG transfer capability of a > + * channel. > + * > + * @max_seg_nr: maximum number of SG segments supported on a SG/SLAVE > + * channel (0 for no maximum or not a SG/SLAVE channel) > + * @max_seg_len: maximum length of SG segments supported on a SG/SLAVE > + * channel (0 for no maximum or not a SG/SLAVE channel) > + */ > +struct dma_slave_sg_caps { > + u32 max_seg_nr; > + u32 max_seg_len; > +}; > + > static inline const char *dma_chan_name(struct dma_chan *chan) > { > return dev_name(&chan->dev->device); > @@ -534,6 +547,7 @@ struct dma_tx_state { > * struct with auxiliary transfer status information, otherwise the call > * will just return a simple status code > * @device_issue_pending: push pending transactions to hardware > + * @device_slave_sg_caps: return the slave SG capabilities > */ > struct dma_device { > > @@ -602,6 +616,9 @@ struct dma_device { > dma_cookie_t cookie, > struct dma_tx_state *txstate); > void (*device_issue_pending)(struct dma_chan *chan); > + struct dma_slave_sg_caps *(*device_slave_sg_caps)( > + struct dma_chan *chan, enum dma_slave_buswidth addr_width, > + u32 maxburst); > }; > > static inline int dmaengine_device_control(struct dma_chan *chan, > @@ -969,6 +986,29 @@ dma_set_tx_state(struct dma_tx_state *st, dma_cookie_t last, dma_cookie_t used, > } > } > > +/** > + * dma_get_slave_sg_caps - get DMAC SG transfer capabilities > + * @chan: target DMA channel > + * @addr_width: address width of the DMA transfer > + * @maxburst: maximum DMA transfer burst size > + * > + * Get SG transfer capabilities for a specified channel. If the dmaengine > + * driver does not implement SG transfer capabilities then NULL is > + * returned. > + */ > +static inline struct dma_slave_sg_caps > +*dma_get_slave_sg_caps(struct dma_chan *chan, > + enum dma_slave_buswidth addr_width, > + u32 maxburst) > +{ > + if (chan->device->device_slave_sg_caps) > + return chan->device->device_slave_sg_caps(chan, > + addr_width, > + maxburst); > + > + return NULL; > +} > + > enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie); > #ifdef CONFIG_DMA_ENGINE > enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx); > -- > 1.7.9.5 >