Subject: [PATCH v4 3/3] dma: Add Freescale eDMA engine driver support

From: [email-masked] (Vinod Koul)
Date: Mon, 2 Sep 2013 16:42:00 +0530

On Mon, Sep 02, 2013 at 07:32:53AM +0000, Lu Jingchang-B35083 wrote:
> > > > > > > +	chan->private = fn_param;
> > > > > > why do you need to use chan->private?
> > > > > [Lu Jingchang]
> > > > > The private used here is to store the slot_id information, which
> > must
> > > > be used
> > > > > by the DMAMUX in alloc_chan_resources function. Thanks.
> > > > Why dont you pass this in struct dma_slave_config memeber slave_id
> > for
> > > > this.
> > > [Lu Jingchang-b35083]
> > > I will drop this private and setup the slave_id directly in the filter
> > function.
> > why in filter? before calling prepare function you can set the slave
> > config
> How about change the filter_fn to follow:
> static bool fsl_edma_filter_fn(struct dma_chan *chan, void *fn_param)
> {
>         struct fsl_edma_filter_param *fparam = fn_param;
>         struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
>         unsigned char val;
> 
>         if (fsl_chan->edmamux->mux_id != fparam->mux_id)
>                 return false;
> 
>         val = EDMAMUX_CHCFG_ENBL | EDMAMUX_CHCFG_SOURCE(fparam->slot_id);
>         fsl_edmamux_config_chan(fsl_chan, val);
>         return true;
> }
> In fact the slot_id isn't need elsewhere, and if the filter return true, 
> This channel should be to this request. So no need to save the slave id, Right?
something like

static bool fsl_edma_filter_fn(struct dma_chan *chan, void *fn_param)
{
	struct fsl_edma_filter_param *fparam = fn_param;
	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);

	if (fsl_chan->edmamux->mux_id != fparam->mux_id)
		return false;
	return true;
}

in thedriver which calls this:

before prep:

	config->slave_id = val;

	dma_set_slave_config(chan, slave);

~Vinod