Re: [PATCH net-next] net: dsa: felix: suppress -EPROBE_DEFER errors

[Michael Walle]

Am 2022-04-07 16:12, schrieb Vladimir Oltean:
> On Thu, Apr 07, 2022 at 04:04:20PM +0200, Michael Walle wrote:
> > Am 2022-04-07 15:56, schrieb Vladimir Oltean:
> > > On Thu, Apr 07, 2022 at 03:06:25PM +0200, Michael Walle wrote:
> > > > Due to missing prerequisites the probe of the felix switch might be
> > > > deferred:
> > > > [    4.435305] mscc_felix 0000:00:00.5: Failed to register DSA
> > > > switch: -517
> > > >
> > > > It's not an error. Use dev_err_probe() to demote the error to a debug
> > > > message. While at it, replace all the dev_err()'s in the probe with
> > > > dev_err_probe().
> > > >
> > > > Signed-off-by: Michael Walle <michael@xxxxxxxx>
> > > > ---
> > >
> > > Please limit the dev_err_probe() to dsa_register_switch(). The resource
> > > that is missing is the DSA master, see of_find_net_device_by_node().
> > > The others cannot possibly return -EPROBE_DEFER.
> >
> > This was my rationale (from the function doc):
> >
> >  * Note that it is deemed acceptable to use this function for error
> >  * prints during probe even if the @err is known to never be 
> > -EPROBE_DEFER.
> >  * The benefit compared to a normal dev_err() is the standardized 
> > format
> >  * of the error code and the fact that the error code is returned.
> >
> > In any case I don't have a strong opinion.
>
> Take this case:
>
>  		err = -ENOMEM;
> -		dev_err(&pdev->dev, "Failed to allocate driver memory\n");
> +		dev_err_probe(&pdev->dev, err, "Failed to allocate driver 
> memory\n");
>
> (1) there is no need to print ENOMEM if we say "failed to allocate 
> memory"

That was actually a brain fart of mine ;) But AFAIK there is no need in
reporting ENOMEM errors anyway.

-michael

> (2) we don't use the return value of dev_err_probe() anyway, we have
>     actual teardown to do (pci_disable_device).
> (3) we _surely_ know that -ENOMEM != -EPROBE_DEFER
> > > >
> > > > Should this be a patch with a Fixes tag?
> > >
> > > Whichever way you wish, no preference.
> >
> > I'll limit it to just the one dev_err() and add a Fixes,
> > there might be scripts out there who greps dmesg for errors.
>
> Ok.