netdev - Re: [RFC PATCH v2 linux-next 13/14] net: dsa: sja1105: expose the SGMII PCS as an mdio

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Message-ID: <20210526212606.k663iljf7a7d2wpi@skbuf>
Date:   Thu, 27 May 2021 00:26:06 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [RFC PATCH v2 linux-next 13/14] net: dsa: sja1105: expose the
 SGMII PCS as an mdio_device

On Wed, May 26, 2021 at 04:46:41PM +0100, Russell King (Oracle) wrote:
> On Wed, May 26, 2021 at 06:41:02PM +0300, Vladimir Oltean wrote:
> > On Wed, May 26, 2021 at 04:29:11PM +0100, Russell King (Oracle) wrote:
> > > On Wed, May 26, 2021 at 04:55:34PM +0300, Vladimir Oltean wrote:
> > > > Since we touch all PCS accessors again, now it is a good time to check
> > > > for error codes from the hardware access as well. We can't propagate the
> > > > errors very far due to phylink returning void for mac_config and
> > > > mac_link_up, but at least we print them to the console.
> > >
> > > phylink doesn't have much option on what it could do if we error out at
> > > those points - I suppose we could print a non-specific error and then
> > > lock-out the interface in a similar way that phylib does, but to me that
> > > seems really unfriendly if you're remotely accessing a box and the error
> > > is intermittent.
> >
> > I would like to have intermittent errors at this level logged, because
> > to me they would be quite unexpected and I would like to have some rope
> > to pull while debugging - an error code, something.
> >
> > If there's an error of any sort, the interface won't be fully
> > initialized anyway, so not functional.
> >
> > The reason why I added error checking in this patch is because I was
> > working on the MDIO bus accessors and I wanted to make sure that the
> > errors returned there are propagated somewhere.
>
> Yes, makes sense there, but doesn't make sense if one is using the MMIO
> accessors and have no errors to check...
>
> My argument is - if you print an error at the lower levels, you can be
> more specific about what failed. If you do it in phylink, you can only
> say "oh, the blah_config() call failed" - which isn't particularly
> useful.
>
> Yes, we do this for some of the newly introduced methods, e.g. the
> pcs_config() method - and there all we can say is:
>
>                 if (err < 0)
>                         phylink_err(pl, "pcs_config failed: %pe\n",
>                                     ERR_PTR(err));

So would you like me to make any change to the code, or is it just that
I mentioned in the commit message that the phylink methods return void?