netdev - Re: [PATCH wpan-next v4 07/11] net: ieee802154: at86rf230: Provide meaningful error codes when possible

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Message-ID: <20220328182835.3e3e1030@xps13>
Date:   Mon, 28 Mar 2022 18:28:35 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Alexander Aring <alex.aring@...il.com>
Cc:     Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan - ML <linux-wpan@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH wpan-next v4 07/11] net: ieee802154: at86rf230: Provide
 meaningful error codes when possible

Hi Alexander,

alex.aring@...il.com wrote on Sun, 27 Mar 2022 11:46:12 -0400:

> Hi,
> 
> On Fri, Mar 18, 2022 at 2:56 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> >
> > Either the spi operation failed, or the offloaded transmit operation
> > failed and returned a TRAC value. Use this value when available or use
> > the default "SYSTEM_ERROR" otherwise, in order to propagate one step
> > above the error.
> >
> > Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> > ---
> >  drivers/net/ieee802154/at86rf230.c | 25 +++++++++++++++++++++++--
> >  1 file changed, 23 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ieee802154/at86rf230.c b/drivers/net/ieee802154/at86rf230.c
> > index d3cf6d23b57e..34d199f597c9 100644
> > --- a/drivers/net/ieee802154/at86rf230.c
> > +++ b/drivers/net/ieee802154/at86rf230.c
> > @@ -358,7 +358,23 @@ static inline void
> >  at86rf230_async_error(struct at86rf230_local *lp,
> >                       struct at86rf230_state_change *ctx, int rc)
> >  {
> > -       dev_err(&lp->spi->dev, "spi_async error %d\n", rc);
> > +       int reason;
> > +
> > +       switch (rc) {  
> 
> I think there was a miscommunication last time, this rc variable is
> not a trac register value, it is a linux errno. Also the error here
> has nothing to do with a trac error. A trac error is the result of the
> offloaded transmit functionality on the transceiver, here we dealing
> about bus communication errors produced by the spi subsystem. What we
> need is to report it to the softmac layer as "IEEE802154_SYSTEM_ERROR"
> (as we decided that this is a user specific error and can be returned
> by the transceiver for non 802.15.4 "error" return code.
> 
> > +       case TRAC_CHANNEL_ACCESS_FAILURE:
> > +               reason = IEEE802154_CHANNEL_ACCESS_FAILURE;
> > +               break;
> > +       case TRAC_NO_ACK:
> > +               reason = IEEE802154_NO_ACK;
> > +               break;
> > +       default:
> > +               reason = IEEE802154_SYSTEM_ERROR;

I went for the solution: if it is a bus error, I return SYSTEM ERROR,
otherwise I return a trac error.

> > +       }
> > +
> > +       if (rc < 0)
> > +               dev_err(&lp->spi->dev, "spi_async error %d\n", rc);
> > +       else
> > +               dev_err(&lp->spi->dev, "xceiver error %d\n", reason);
> >
> >         at86rf230_async_state_change(lp, ctx, STATE_FORCE_TRX_OFF,
> >                                      at86rf230_async_error_recover);
> > @@ -666,10 +682,15 @@ at86rf230_tx_trac_check(void *context)
> >         case TRAC_SUCCESS:
> >         case TRAC_SUCCESS_DATA_PENDING:
> >                 at86rf230_async_state_change(lp, ctx, STATE_TX_ON, at86rf230_tx_on);
> > +               return;
> > +       case TRAC_CHANNEL_ACCESS_FAILURE:
> > +       case TRAC_NO_ACK:
> >                 break;
> >         default:
> > -               at86rf230_async_error(lp, ctx, -EIO);
> > +               trac = TRAC_INVALID;
> >         }
> > +
> > +       at86rf230_async_error(lp, ctx, trac);  
> 
> That makes no sense, at86rf230_async_error() is not a trac error
> handling, it is a bus error handling. As noted above. With this change
> you mix bus errors and trac errors (which are not bus errors). If
> there are no bus errors then trac should be evaluated and should
> either deliver some 802.15.4 $SUCCESS_CODE or $ERROR_CODE to the
> softmac stack, which is xmit_complete() or xmit_error().

There is no specific path for bus errors, everything is supposedly
asynchronous and all the function return void. In both cases I need to
free the skb. So I am questioning myself about the right solution (need
to think further...)

Thanks,
Miquèl