linux-kernel - Re: [PATCH RFC v2 07/18] cxl/mem: Expose device dynamic capacity configuration

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Date:   Tue, 5 Sep 2023 13:45:40 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        <ira.weiny@...el.com>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Navneet Singh <navneet.singh@...el.com>,
        Fan Ni <fan.ni@...sung.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dave Jiang <dave.jiang@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 07/18] cxl/mem: Expose device dynamic capacity
 configuration

Jonathan Cameron wrote:
> On Mon, 28 Aug 2023 22:20:58 -0700
> ira.weiny@...el.com wrote:
> 
> > From: Navneet Singh <navneet.singh@...el.com>
> > 
> > To properly configure CXL regions on Dynamic Capacity Devices (DCD),
> > user space will need to know the details of the DC Regions available on
> > a device.
> > 
> > Expose driver dynamic capacity configuration through sysfs
> > attributes.
> > 
> > Co-developed-by: Navneet Singh <navneet.singh@...el.com>
> > Signed-off-by: Navneet Singh <navneet.singh@...el.com>
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > 
> One trivial comment inline.  I wondered a bit if it would
> be better to not present dc at all on devices that don't support
> dynamic capacity, but for now there isn't an elegant way to do that
> (some discussions and patches are flying around however so maybe this
>  will be resolved before this series merges giving us that elegant
>  option).

For now I will keep this yes.  But if there is a better way then sure.

> 
> With commented code tidied up
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> 

Thanks.

> > diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> > index 492486707fd0..397262e0ebd2 100644
> > --- a/drivers/cxl/core/memdev.c
> > +++ b/drivers/cxl/core/memdev.c
> > @@ -101,6 +101,20 @@ static ssize_t pmem_size_show(struct device *dev, struct device_attribute *attr,
> >  static struct device_attribute dev_attr_pmem_size =
> >  	__ATTR(size, 0444, pmem_size_show, NULL);
> >  
> > +static ssize_t region_count_show(struct device *dev, struct device_attribute *attr,
> > +				 char *buf)
> > +{
> > +	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
> > +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
> > +	int len = 0;
> > +
> > +	len = sysfs_emit(buf, "%d\n", mds->nr_dc_region);
> > +	return len;
> 
> return sysfs_emit(buf, "...);
> 	

Done thanks!
Ira