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Date:   Wed, 29 Mar 2023 21:35:17 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Daniel Golle <daniel@makrotopia.org>
Cc:     netdev@vger.kernel.org, linux-mediatek@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Florian Fainelli <f.fainelli@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Sean Wang <sean.wang@mediatek.com>,
        Landen Chao <Landen.Chao@mediatek.com>,
        DENG Qingfang <dqfext@gmail.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Sam Shih <Sam.Shih@mediatek.com>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        John Crispin <john@phrozen.org>, Felix Fietkau <nbd@nbd.name>
Subject: Re: [RFC PATCH net-next v3 03/15] net: dsa: mt7530: use regmap to
 access switch register space
Message-ID: <e8bb79ab-94d2-4e36-9b75-576a47e6c126@lunn.ch>
References: <cover.1680105013.git.daniel@makrotopia.org>
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 <7eb07ed2-2b1c-44fa-b029-0ecad7872fd2@lunn.ch>
 <ZCSEbUt9kj8Ta6Yc@makrotopia.org>
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On Wed, Mar 29, 2023 at 07:33:17PM +0100, Daniel Golle wrote:
> On Wed, Mar 29, 2023 at 06:24:21PM +0200, Andrew Lunn wrote:
> > Thanks for splitting this patchset up. This is much easier to review.
> > 
> > > +static u32
> > > +mt7530_mii_read(struct mt7530_priv *priv, u32 reg)
> > > +{
> > > +	int ret;
> > > +	u32 val;
> > > +
> > > +	ret = regmap_read(priv->regmap, reg, &val);
> > > +	if (ret) {
> > > +		dev_err(priv->dev,
> > > +			"failed to read mt7530 register\n");
> > > +		return ret;
> > 
> > This is a u32 function. ret should be negative on error, which is
> > going to be turned positive in order to return a u32. So you probably
> > want to make this an int function.
> 
> This is a pre-existing flaw in the code. As we are accessing 32-bit
> registers there has just never been any meaningful error handling.

O.K. At least i would not return the negative error code. Return 0, or
0xdeadbeef or something. And consider adding a WARN_ON_ONCE() so it is very loud
when it goes wrong.

> I guess the correct solution would be to not use the return value only
> to indicate success or error, and use an additional u32* parameter for
> the read value.

Yes, that is what mv88e6xxx does.

> However, I was hestitating to convert all the calls (they are many) to
> follow that improved paradigm.

Yes, leave that for another time.

     Andrew