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

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Message-ID: <aXI2bWhDtNNfr8M8@smile.fi.intel.com>
Date: Thu, 22 Jan 2026 16:38:37 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-kernel@...r.kernel.org,
	Herve Codina <herve.codina@...tlin.com>,
	Mark Brown <broonie@...nel.org>,
	Serge Semin <fancer.lancer@...il.com>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>,
	Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
	Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
	Jiawen Wu <jiawenwu@...stnetic.com>
Subject: Re: [PATCH v2 net-next 01/15] net: mdio-regmap: permit working with
 non-MMIO regmaps

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