linux-kernel - Re: [PATCH v3 06/18] cxl/region: Rename function to cxl_find_decoder

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Message-ID: <Z8hIHQkMxrfhKlq6@rric.localdomain>
Date: Wed, 5 Mar 2025 13:48:29 +0100
From: Robert Richter <rrichter@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.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 v3 06/18] cxl/region: Rename function to
 cxl_find_decoder_early()

On 14.02.25 15:58:08, Jonathan Cameron wrote:
> On Tue, 11 Feb 2025 10:53:36 +0100
> Robert Richter <rrichter@....com> wrote:
> 
> > Current function cxl_region_find_decoder() is used to find a port's
> > decoder during region setup. The decoder is later used to attach the
> > port to a region.
> > 
> > Rename function to cxl_find_decoder_early() to emphasize its use only
> > during region setup in the early setup stage. Once a port is attached
> > to a region, the region reference can be used to lookup a region's
> > port and decoder configuration (see struct cxl_region_ref).
> 
> Early doesn't seem that well defined to me. Can we indicate what the state
> is more explicitly?

'early' is used here as common term in the kernel to run pre-init
code. Here that means, an endpoint is not yet attached to a region
(cxl_region_attach()).

> 
> Or does it actually matter?  Whilst there is a better way to get
> it later, does this function then return the wrong answer?

There region references are setup and should be used then.

> 
> Or if we have both cases of 'finding' it, can we just make this
> code do both?

No, there is no user.

I will update description and comment in the code to better explain
the 'early' state.

-Robert

> 
> Jonathan
> 
> > 
> > Signed-off-by: Robert Richter <rrichter@....com>
> > Reviewed-by: Gregory Price <gourry@...rry.net>
> > Tested-by: Gregory Price <gourry@...rry.net>
> > ---
> >  drivers/cxl/core/region.c | 17 ++++++++++++-----
> >  1 file changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index 54afdb0fa61c..13e3ba984a53 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -850,10 +850,17 @@ static int match_auto_decoder(struct device *dev, const void *data)
> >  	return 0;
> >  }
> >  
> > +/*
> > + * Use cxl_find_decoder_early() only during region setup in the early
> > + * setup stage. Once a port is attached to a region, the region
> > + * reference can be used to lookup a region's port and decoder
> > + * configuration (see struct cxl_region_ref).
> > +*/
> > +
> >  static struct cxl_decoder *
> > -cxl_region_find_decoder(struct cxl_port *port,
> > -			struct cxl_endpoint_decoder *cxled,
> > -			struct cxl_region *cxlr)
> > +cxl_find_decoder_early(struct cxl_port *port,
> > +		       struct cxl_endpoint_decoder *cxled,
> > +		       struct cxl_region *cxlr)
> >  {
> >  	struct device *dev;
> >  
> > @@ -917,7 +924,7 @@ alloc_region_ref(struct cxl_port *port, struct cxl_region *cxlr,
> >  		if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
> >  			struct cxl_decoder *cxld;
> >  
> > -			cxld = cxl_region_find_decoder(port, cxled, cxlr);
> > +			cxld = cxl_find_decoder_early(port, cxled, cxlr);
> >  			if (auto_order_ok(port, iter->region, cxld))
> >  				continue;
> >  		}
> > @@ -1005,7 +1012,7 @@ static int cxl_rr_alloc_decoder(struct cxl_port *port, struct cxl_region *cxlr,
> >  {
> >  	struct cxl_decoder *cxld;
> >  
> > -	cxld = cxl_region_find_decoder(port, cxled, cxlr);
> > +	cxld = cxl_find_decoder_early(port, cxled, cxlr);
> >  	if (!cxld) {
> >  		dev_dbg(&cxlr->dev, "%s: no decoder available\n",
> >  			dev_name(&port->dev));
>