Re: [PATCH net-next v2 5/8] net: dsa: mt7530: replace mt7530_read with regmap_read

[Jakub Kicinski <kuba@kernel.org>]

On Mon, 15 Jun 2026 16:56:49 -0700 Jakub Kicinski wrote:
> >  static u32
> > -mt7530_read(struct mt7530_priv *priv, u32 reg)
> > +mt7530_mii_poll(struct mt7530_dummy_poll *p)
> >  {
> > -	int ret;
> >  	u32 val;
> >  
> > -	ret = regmap_read(priv->regmap, reg, &val);
> > -	if (ret) {
> > -		WARN_ON_ONCE(1);
> > -		dev_err(priv->dev,
> > -			"failed to read mt7530 register\n");
> > -		return 0;
> > -	}
> > +	regmap_read(p->priv->regmap, p->reg, &val);
> >  
> >  	return val;
> >  }  
> 
> [Medium]
> The old wrapper guaranteed val == 0 on failure. The new mt7530_mii_poll()
> declares val without an initializer and ignores the regmap_read() return
> code, so on a failed underlying transfer val is whatever was on the stack.
> 
> Looking at drivers/net/dsa/mt7530-mdio.c::mt7530_regmap_read():
> 
>     ret = bus->write(bus, priv->mdiodev->addr, 0x1f, page);
>     if (ret < 0)
>         return ret;
> 
>     lo = bus->read(bus, priv->mdiodev->addr, r);
>     hi = bus->read(bus, priv->mdiodev->addr, 0x10);
> 
>     *val = (hi << 16) | (lo & 0xffff);

This looks legit, AFAICT, sadly.

Maybe just write *val = 0; in mt7530_regmap_read() unconditionally ?