Re: [PATCH 05/18] cxl/region: Add volatile region creation support

[Dan Williams <dan.j.williams@intel.com>]

Dave Jiang wrote:
> 
> 
> On 2/5/23 6:02 PM, Dan Williams wrote:
> > Expand the region creation infrastructure to enable 'ram'
> > (volatile-memory) regions. The internals of create_pmem_region_store()
> > and create_pmem_region_show() are factored out into helpers
> > __create_region() and __create_region_show() for the 'ram' case to
> > reuse.
> > 
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> 
> Minor comment below, otherwise:
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> 
[..]
> > diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> > index 4c4e1cbb1169..3acf2f17a73f 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-cxl
> > +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> > @@ -285,20 +285,20 @@ Description:
> >   		interleave_granularity).
> >   
> >   
> > -What:		/sys/bus/cxl/devices/decoderX.Y/create_pmem_region
> > -Date:		May, 2022
> > -KernelVersion:	v6.0
> > +What:		/sys/bus/cxl/devices/decoderX.Y/create_{pmem,ram}_region
> > +Date:		May, 2022, January, 2023
> > +KernelVersion:	v6.0 (pmem), v6.3 (ram)
> >   Contact:	linux-cxl@vger.kernel.org
> >   Description:
> >   		(RW) Write a string in the form 'regionZ' to start the process
> > -		of defining a new persistent memory region (interleave-set)
> > -		within the decode range bounded by root decoder 'decoderX.Y'.
> > -		The value written must match the current value returned from
> > -		reading this attribute. An atomic compare exchange operation is
> > -		done on write to assign the requested id to a region and
> > -		allocate the region-id for the next creation attempt. EBUSY is
> > -		returned if the region name written does not match the current
> > -		cached value.
> > +		of defining a new persistent, or volatile memory region
> > +		(interleave-set) within the decode range bounded by root decoder
> > +		'decoderX.Y'. The value written must match the current value
> > +		returned from reading this attribute. An atomic compare exchange
> > +		operation is done on write to assign the requested id to a
> > +		region and allocate the region-id for the next creation attempt.
> > +		EBUSY is returned if the region name written does not match the
> 
> -EBUSY?

Userspace errno values are positive. So "$?" after "echo $region >
create_pmem_region" will be 16 not -16 in the busy case.