linux-kernel - Re: [PATCH 06/26] cxl/port: Add Dynamic Capacity mode support to endpoint decoders

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Date: Fri, 5 Apr 2024 12:50:06 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: fan <nifan.cxl@...il.com>, <ira.weiny@...el.com>
CC: Dave Jiang <dave.jiang@...el.com>, Fan Ni <fan.ni@...sung.com>, "Jonathan
 Cameron" <Jonathan.Cameron@...wei.com>, Navneet Singh
	<navneet.singh@...el.com>, Dan Williams <dan.j.williams@...el.com>, Davidlohr
 Bueso <dave@...olabs.net>, Alison Schofield <alison.schofield@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>, <linux-btrfs@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/26] cxl/port: Add Dynamic Capacity mode support to
 endpoint decoders

fan wrote:
> On Sun, Mar 24, 2024 at 04:18:09PM -0700, ira.weiny@...el.com wrote:
> > From: Navneet Singh <navneet.singh@...el.com>
> > 

[snip]

> > diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> > index 66b8419fd0c3..e22b6f4f7145 100644
> > --- a/drivers/cxl/core/hdm.c
> > +++ b/drivers/cxl/core/hdm.c
> > @@ -255,6 +255,14 @@ static void devm_cxl_dpa_release(struct cxl_endpoint_decoder *cxled)
> >  	__cxl_dpa_release(cxled);
> >  }
> >  
> > +static int dc_mode_to_region_index(enum cxl_decoder_mode mode)
> > +{
> > +	if (mode < CXL_DECODER_DC0 || CXL_DECODER_DC7 < mode)
> 
> To me, it is more natural to have something like x<a || x>b other than
> x<a || b < x for out of range check.

Ok.


[snip]

> >  
> >  	guard(rwsem_write)(&cxl_dpa_rwsem);
> >  	if (cxled->cxld.flags & CXL_DECODER_F_ENABLE)
> > @@ -433,6 +442,16 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
> >  			return -ENXIO;
> >  		}
> >  		break;
> > +	case CXL_DECODER_DC0 ... CXL_DECODER_DC7:
> > +		rc = dc_mode_to_region_index(mode);
> > +		if (rc < 0)
> > +			return rc;
> > +
> > +		if (resource_size(&cxlds->dc_res[rc]) == 0) {
> 
> The other similar checks above use "!resource_size(...)".
> 

Yea good catch.
Ira