linux-kernel - Re: [RFC PATCH 1/3] dmaengine: add dma_get_channel

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Date:	Wed, 9 Jan 2013 20:59:56 -0500
From:	Matt Porter <mporter@...com>
To:	Vinod Koul <vkoul@...radead.org>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	vinod.koul@...el.com, Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dan Williams <djbw@...com>, Chris Ball <cjb@...top.org>
Subject: Re: [RFC PATCH 1/3] dmaengine: add dma_get_channel_caps()

On Wed, Oct 24, 2012 at 08:43:27AM +0530, Vinod Koul wrote:
> On Tue, 2012-10-23 at 23:49 +0100, Grant Likely wrote:
> > > +enum dmaengine_apis {
> > > +       DMAENGINE_MEMCPY        = 0x0001,
> > > +       DMAENGINE_XOR           = 0x0002,
> > > +       DMAENGINE_XOR_VAL       = 0x0004,
> > > +       DMAENGINE_PQ            = 0x0008,
> > > +       DMAENGINE_PQ_VAL        = 0x0010,
> > > +       DMAENGINE_MEMSET        = 0x0020,
> > > +       DMAENGINE_SLAVE         = 0x0040,
> > > +       DMAENGINE_CYCLIC        = 0x0080,
> > > +       DMAENGINE_INTERLEAVED   = 0x0100,
> > > +       DMAENGINE_SG            = 0x0200,
> > > +};
> > 
> > Actually, one more comment. Why the new enum? Why can't the
> > dma_transaction_type enum be used directly along with dma_cap_mask_t? 
> Some of the capabilities above are not there in dma_caps_t like DMA_SG.
> Also DMA_INTERRUPT and DMA_PRIVATE would not make much sense here.
> 
> BUT would help to keep things simpler if have one definition which
> includes all.

All good points. I think we can best eliminate this redundant set of 
enums by using dma_cap_mask_t and noting in a comment as follows:

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 0181887..9add5ca 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -391,14 +391,15 @@ enum dmaengine_apis {
  * a) APIs/ops supported
  * b) channel physical capabilities
  *
- * @ops: or'ed api capability
+ * @cap_mask: api/ops capability (DMA_INTERRUPT and DMA_PRIVATE
+ *	       are invalid api/ops and will never be set)
  * @seg_nr: maximum number of SG segments supported on a SG/SLAVE
  *	    channel (0 for no maximum or not a SG/SLAVE channel)
  * @seg_len: maximum length of SG segments supported on a SG/SLAVE
  *	     channel (0 for no maximum or not a SG/SLAVE channel)
  */
 struct dmaengine_chan_caps {
-	enum dmaengine_apis ops;
+	dma_cap_mask_t cap_mask;
 	int seg_nr;
 	int seg_len;
 };

If that sounds good I'll send an updated series with this change.

-Matt
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