linux-kernel - Re: [PATCH v3 08/15] dmaengine: dw: revisit data

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Date:	Wed, 13 Apr 2016 21:47:15 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	Viresh Kumar <vireshk@...nel.org>, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Hans-Christian Egtvedt <egtvedt@...fundet.no>,
	Tejun Heo <tj@...nel.org>, Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Rutland <mark.rutland@....com>,
	Vineet Gupta <vgupta@...opsys.com>
Subject: Re: [PATCH v3 08/15] dmaengine: dw: revisit data_width property

On Wed, Apr 13, 2016 at 07:05:48PM +0300, Andy Shevchenko wrote:
> On Wed, 2016-04-13 at 21:27 +0530, Vinod Koul wrote:
> > On Fri, Mar 18, 2016 at 04:24:47PM +0200, Andy Shevchenko wrote:
> > The driver should still work with older DT implementation, so you need
> > to
> > keep support for that in driver and hence I don't see any benfit we
> > would
> > get from doing both in driver!
> 
> The device tree is screwed by a process that allows to do almost
> whatever you want. Here I'm trying to rectify the usage of the field.

Well at least we should try to do the right thing which means pushing back
on ABI breakage..

> The old is still supported and benefit is apparently in unifying
> standard properties across the drivers.

Hrmmm how is that?

> > > @@ -102,8 +102,8 @@ dw_dma_parse_dt(struct platform_device *pdev)
> > >  {
> > >  	struct device_node *np = pdev->dev.of_node;
> > >  	struct dw_dma_platform_data *pdata;
> > > -	u32 tmp, arr[DW_DMA_MAX_NR_MASTERS];
> > >  	u32 nr_channels;
> > > +	u32 tmp;
> > >  
> > >  	if (!np) {
> > >  		dev_err(&pdev->dev, "Missing DT data\n");
> > > @@ -138,10 +138,10 @@ dw_dma_parse_dt(struct platform_device *pdev)
> > >  		pdata->nr_masters = tmp;
> > >  	}
> > >  
> > > -	if (!of_property_read_u32_array(np, "data_width", arr,
> > > -				pdata->nr_masters))
> > > -		for (tmp = 0; tmp < pdata->nr_masters; tmp++)
> > > -			pdata->data_width[tmp] = arr[tmp];

You stop reading the array

> > > +	if (!of_property_read_u32(np, "data-width", &tmp))
> > > +		pdata->data_width = tmp;
> > > +	else if (!of_property_read_u32(np, "data_width", &tmp))
> > > +		pdata->data_width = BIT(tmp & 0x07);

And read a value? how will this work with older array?

-- 
~Vinod