On Wed, Jul 11, 2018 at 04:27:15PM -0700, Paul Burton wrote:

Hi Vinod,

On Wed, Jul 11, 2018 at 05:46:55PM +0530, Vinod wrote:

quoted

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 -	jzdma->base = devm_ioremap_resource(dev, res);
 -	if (IS_ERR(jzdma->base))
 -		return PTR_ERR(jzdma->base);
 +	jzdma->chn_base = devm_ioremap_resource(dev, res);
 +	if (IS_ERR(jzdma->chn_base))
 +		return PTR_ERR(jzdma->chn_base);
 +
 +	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 +	if (!res) {
 +		dev_err(dev, "failed to get I/O memory\n");
 +		return -EINVAL;
 +	}

okay and this breaks if you happen to get probed on older DT. I think DT
is treated as ABI so you need to continue support older method while
finding if DT has split resources

See my response to PrasannaKumar. All the Ingenic-based boards do compile
the devicetree within the kernel, so I think it's still fine to add breaking
changes. I'll wait on @Rob to give his point of view on this, though.

(It's not something hard to change, but I'd like to know what's the policy
in that case. I have other DT-breaking patches to submit)

The policy is that DT is an ABI and should not break :)

I think in general that's a good policy to have for compatibility, but
if it's known for certain that the DT for all users of a driver is
always built into the kernel then I don't see why we shouldn't feel free
to change a binding. I agree with Paul that it'd be interesting to hear
the DT binding maintainers take on this.

If the platform maintainers (and their users) don't care, then I don't 
have an issue with the change. It should still be an exception and not 
just any change goes. The commit message should still highlight that 
compatibility is being broken and why.

Rob