linux-kernel - Re: [PATCH v3 06/11] cxl/region: Separate region parameter setup and region construction

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Message-ID: <aMfA1hlZWfNdnEy5@rric.localdomain>
Date: Mon, 15 Sep 2025 09:31:34 +0200
From: Robert Richter <rrichter@....com>
To: Dave Jiang <dave.jiang@...el.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>,
	Jonathan Cameron <Jonathan.Cameron@...wei.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>,
	Joshua Hahn <joshua.hahnjy@...il.com>
Subject: Re: [PATCH v3 06/11] cxl/region: Separate region parameter setup and
 region construction

On 12.09.25 14:10:06, Dave Jiang wrote:
> 
> 
> On 9/12/25 7:45 AM, Robert Richter wrote:
> > To construct a region, the region parameters such as address range and
> > interleaving config need to be determined. This is done while
> > constructing the region by inspecting the endpoint decoder
> > configuration. The endpoint decoder is passed as a function argument.
> > 
> > With address translation the endpoint decoder data is no longer
> > sufficient to extract the region parameters as some of the information
> > is obtained using other methods such as using firmware calls.
> > 
> > In a first step, separate code to determine and setup the region
> > parameters from the region construction. Temporarily store all the
> > data to create the region in the new struct cxl_region_context. Add a
> > new function setup_region_parameters() to fill that struct and later
> > use it to construct the region. This simplifies the extension of the
> > function to support other methods needed, esp. to support address
> > translation.
> > 
> > Patch is a prerequisite to implement address translation.
> > 
> > Signed-off-by: Robert Richter <rrichter@....com>
> > ---
> >  drivers/cxl/core/region.c | 50 +++++++++++++++++++++++++++++----------
> >  1 file changed, 38 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index 106692f1e310..57697504410b 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -3414,6 +3414,26 @@ static int match_region_by_range(struct device *dev, const void *data)
> >  	return 0;
> >  }
> >  
> > +struct cxl_region_context {
> > +	struct cxl_endpoint_decoder *cxled;
> > +	struct cxl_memdev *cxlmd;
> > +	struct range hpa_range;
> > +	int interleave_ways;
> > +	int interleave_granularity;
> > +};
> > +
> > +static int setup_region_params(struct cxl_endpoint_decoder *cxled,
> > +			       struct cxl_region_context *ctx)
> > +{
> > +	ctx->cxled = cxled;
> > +	ctx->cxlmd = cxled_to_memdev(cxled);
> > +	ctx->hpa_range = cxled->cxld.hpa_range;
> > +	ctx->interleave_ways = cxled->cxld.interleave_ways;
> > +	ctx->interleave_granularity = cxled->cxld.interleave_granularity;
> 
> You can init like this:
> 
> 	*ctx = (struct cxl_region_context) {
> 		.cxled = cxled,
> 		.cxlmd = cxled_to_memdev(cxled),
> 		.hpa_range = cxled->cxld.hpa_range,
> 		.interleave_ways = cxled->cxld.interleave_ways,
> 		.interleave_granularity = cxled->cxld.interleave_granularity,
> 	};

Will change that for readability and to zero-init possibly missing
members.

> 
> 
> > +
> > +	return 0;
> 
> Can probably make this function void if no expected errors and only assignments.

A later extension to the code may return an error code, so I prepared
the function interface already for this.

-Robert

> 
> DJ