Subject: Re: [PATCH v2 net-next 01/15] net: mdio-regmap: permit working with non-MMIO regmaps

From: Andy Shevchenko <[email-masked]>
Date: Thu, 22 Jan 2026 16:38:37 +0200

On Thu, Jan 22, 2026 at 03:47:04PM +0200, Vladimir Oltean wrote:
> On Thu, Jan 22, 2026 at 02:13:01PM +0200, Vladimir Oltean wrote:

...

> > > > +	unsigned int base;
> > > Hmm... resource_size_t ?

> > Well, regmap_read() takes "unsigned int reg".
> > https://elixir.bootlin.com/linux/v6.18.6/source/include/linux/regmap.h#L1297
> > So in practice, a truncation will be done somewhere if the register base
> > exceeds unsigned int storage capacity. But I didn't feel that it's worth
> > handling that.
> 
> Would this address your feedback?

Yes and no. See my remarks below.

> diff --git a/drivers/net/mdio/mdio-regmap.c b/drivers/net/mdio/mdio-regmap.c
> index 2a0e9c519fa3..416ff4e13e8f 100644
> --- a/drivers/net/mdio/mdio-regmap.c
> +++ b/drivers/net/mdio/mdio-regmap.c
> @@ -67,8 +67,15 @@ struct mii_bus *devm_mdio_regmap_register(struct device *dev,
>  	mr = mii->priv;
>  	mr->regmap = config->regmap;
>  	mr->valid_addr = config->valid_addr;
> -	if (config->resource)
> +	if (config->resource) {

Btw, this might be not enough, one should check size and flags as well
before use. There was a discussion about this recently. Maybe we should
just move to a simple unsigned int in the config for now? Because handling
resources maybe considered as over engineering in this case.

> +		if (config->resource->start > U32_MAX ||
> +		    config->resource->end > U32_MAX) {

Ideally it should be resource_overlaps() check. But see above.

> +			dev_err(config->parent,
> +				"Resource exceeds regmap API addressing possibilities\n");
> +			return ERR_PTR(-EINVAL);
> +		}
>  		mr->base = config->resource->start;
> +	}

-- 
With Best Regards,
Andy Shevchenko