linux-kernel - Re: [PATCH v1 28/29] cxl/region: Show message on broken target list

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Message-ID: <20250207175139.00007ad6@huawei.com>
Date: Fri, 7 Feb 2025 17:51:39 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Robert Richter <rrichter@....com>
CC: Alison Schofield <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Dave Jiang <dave.jiang@...el.com>, "Davidlohr
 Bueso" <dave@...olabs.net>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Gregory Price <gourry@...rry.net>, "Fabio M.
 De Francesco" <fabio.m.de.francesco@...ux.intel.com>, Terry Bowman
	<terry.bowman@....com>
Subject: Re: [PATCH v1 28/29] cxl/region: Show message on broken target list

On Thu, 6 Feb 2025 22:23:40 +0100
Robert Richter <rrichter@....com> wrote:

> On 14.01.25 11:16:41, Jonathan Cameron wrote:
> > On Tue, 7 Jan 2025 15:10:14 +0100
> > Robert Richter <rrichter@....com> wrote:
> >   
> > > Broken target lists are hard to discover as the driver fails at a
> > > later initialization stage. Add an error message for this.
> > > 
> > > Signed-off-by: Robert Richter <rrichter@....com>
> > > ---
> > >  drivers/cxl/core/region.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > > index 775450a1a887..2af3b6c14f46 100644
> > > --- a/drivers/cxl/core/region.c
> > > +++ b/drivers/cxl/core/region.c
> > > @@ -1870,6 +1870,13 @@ static int find_pos_and_ways(struct cxl_port *port, struct range *range,
> > >  	}
> > >  	put_device(dev);
> > >  
> > > +	if (rc)
> > > +		dev_err(port->uport_dev,
> > > +			"failed to find %s:%s in target list of %s\n",
> > > +			dev_name(&port->dev),
> > > +			dev_name(port->parent_dport->dport_dev),
> > > +			dev_name(&cxlsd->cxld.dev));
> > > +
> > >  	return rc;
> > >  }  
> > This function would benefit from some __free() magic dust.
> > Then we could return in the good path in the loop and not need the if (rc)
> > check here.  
> 
> That does not really simplify the code. It would just this one
> indentation. On the other side there is a central exit for the code
> and we just need only that one put_device(). Plus, I like to have the
> 'success' code path returning at the end of block.

Seems simpler to me to return early on finding a match.

static int find_pos_and_ways(struct cxl_port *port, struct range *range,
			     int *pos, int *ways)
{
	struct cxl_switch_decoder *cxlsd;
	struct cxl_port *parent;

	parent = next_port(port);
	if (!parent)
		return -ENXIO;

	struct device *dev __free(device) =
		device_find_child(&parent->dev, range,
				  match_switch_decoder_by_range);
	if (!dev) {
		dev_err(port->uport_dev,
			"failed to find decoder mapping %#llx-%#llx\n",
			range->start, range->end);
		return -ENODEV;
	}
	cxlsd = to_cxl_switch_decoder(dev);
	*ways = cxlsd->cxld.interleave_ways;

	for (int i = 0; i < *ways; i++) {
		if (cxlsd->target[i] == port->parent_dport) {
			*pos = i;
			return 0;
		}
	}
	dev_err(port->uport_dev,
		"failed to find %s:%s in target list of %s\n",
		dev_name(&port->dev),
		dev_name(port->parent_dport->dport_dev),
		dev_name(&cxlsd->cxld.dev));

	return -ENXIO;
}

I don't mind that much though.  I'd also suggest returning -ENXIO
doesn't seem the right choice for failing to find something.


> 
> -Robert
> 
> > 
> > Otherwise looks fine.
> > 
> > Jonathan
> >   
> > >    
> >   
>