netdev - Re: [PATCH v23 17/22] cxl/region: Factor out interleave ways setup

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Message-ID: <383d7089-d7ca-43ab-8284-694e60729770@amd.com>
Date: Wed, 11 Feb 2026 16:11:21 -0600
From: "Cheatham, Benjamin" <benjamin.cheatham@....com>
To: <alejandro.lucero-palau@....com>
CC: Alejandro Lucero <alucerop@....com>, Zhi Wang <zhiw@...dia.com>, "Jonathan
 Cameron" <Jonathan.Cameron@...wei.com>, Alison Schofield
	<alison.schofield@...el.com>, <linux-cxl@...r.kernel.org>,
	<netdev@...r.kernel.org>, <dan.j.williams@...el.com>, <edward.cree@....com>,
	<davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<edumazet@...gle.com>, <dave.jiang@...el.com>
Subject: Re: [PATCH v23 17/22] cxl/region: Factor out interleave ways setup

On 2/1/2026 9:54 AM, alejandro.lucero-palau@....com wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> Region creation based on Type3 devices is triggered from user space
> allowing memory combination through interleaving.
> 
> In preparation for kernel driven region creation, that is Type2 drivers
> triggering region creation backed with its advertised CXL memory, factor
> out a common helper from the user-sysfs region setup for interleave ways.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> Reviewed-by: Zhi Wang <zhiw@...dia.com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Reviewed-by: Ben Cheatham <benjamin.cheatham@....com>
> Reviewed-by: Alison Schofield <alison.schofield@...el.com>
> ---
>  drivers/cxl/core/region.c | 43 ++++++++++++++++++++++++---------------
>  1 file changed, 27 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index f53b2e9fd9e6..ece1d3df7cf1 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -485,22 +485,14 @@ static ssize_t interleave_ways_show(struct device *dev,
>  
>  static const struct attribute_group *get_cxl_region_target_group(void);
>  
> -static ssize_t interleave_ways_store(struct device *dev,
> -				     struct device_attribute *attr,
> -				     const char *buf, size_t len)
> +static int set_interleave_ways(struct cxl_region *cxlr, int val)

@val should probably stay an unsigned int. You pass an unsigned int in the sysfs function, and the
function was originally coded with that in mind (same with @save below). With that cleaned up:
Reviewed-by: Ben Cheatham <benjamin.cheatham@....com>

>  {
> -	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev->parent);
> +	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
>  	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
> -	struct cxl_region *cxlr = to_cxl_region(dev);
>  	struct cxl_region_params *p = &cxlr->params;
> -	unsigned int val, save;
> -	int rc;
> +	int save, rc;
>  	u8 iw;
>  
> -	rc = kstrtouint(buf, 0, &val);
> -	if (rc)
> -		return rc;
> -
>  	rc = ways_to_eiw(val, &iw);
>  	if (rc)
>  		return rc;
> @@ -515,9 +507,7 @@ static ssize_t interleave_ways_store(struct device *dev,
>  		return -EINVAL;
>  	}
>  
> -	ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region);
> -	if ((rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem)))
> -		return rc;
> +	lockdep_assert_held_write(&cxl_rwsem.region);
>  
>  	if (p->state >= CXL_CONFIG_INTERLEAVE_ACTIVE)
>  		return -EBUSY;
> @@ -525,10 +515,31 @@ static ssize_t interleave_ways_store(struct device *dev,
>  	save = p->interleave_ways;
>  	p->interleave_ways = val;
>  	rc = sysfs_update_group(&cxlr->dev.kobj, get_cxl_region_target_group());
> -	if (rc) {
> +	if (rc)
>  		p->interleave_ways = save;
> +
> +	return rc;
> +}
> +
> +static ssize_t interleave_ways_store(struct device *dev,
> +				     struct device_attribute *attr,
> +				     const char *buf, size_t len)
> +{
> +	struct cxl_region *cxlr = to_cxl_region(dev);
> +	unsigned int val;
> +	int rc;
> +
> +	rc = kstrtouint(buf, 0, &val);
> +	if (rc)
> +		return rc;
> +
> +	ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region);
> +	if ((rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem)))
> +		return rc;
> +
> +	rc = set_interleave_ways(cxlr, val);
> +	if (rc)
>  		return rc;
> -	}
>  
>  	return len;
>  }