Re: [ndctl PATCH 3/7] libcxl: apply CXL_CAPACITY_MULTIPLIER to partition alignment field

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Thu, 2022-01-06 at 12:40 -0800, Ira Weiny wrote:
> On Mon, Jan 03, 2022 at 12:16:14PM -0800, Schofield, Alison wrote:
> > From: Alison Schofield <alison.schofield@intel.com>
> > 
> > The IDENTIFY mailbox command returns the partition alignment field
> > expressed in multiples of 256 MB.
> 
> Interesting...
> 
> I don't think anyone is using this function just yet but this does technically
> change the behavior of this function.
> 
> Will that break anyone or cxl-cli?
> 
> > Use CXL_CAPACITY_MULTIPLIER when
> > returning this field.
> > 
> > This is in sync with all the other partitioning related fields using
> > the multiplier.
> 
> To me the fact that this was not in bytes implies that the original API of
> libcxl was intended to not convert these values.
> 
> Vishal may have an opinion.  Should these be in bytes or 'CXL Capacity' units
> (ie 256MB's)?
> 
> I think I prefer bytes as well.

Hm yeah there's not an internal (i.e. cxl-cli) user yet. I think bytes
makes sense. It is common for libcxl to convert spec-isms to whatever
makes sense at the library/cxl-cli level, and for that bytes makes
sense.

> 
> Ira
> 
> > 
> > Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> > ---
> >  cxl/lib/libcxl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
> > index 715d8e4..85a6c0e 100644
> > --- a/cxl/lib/libcxl.c
> > +++ b/cxl/lib/libcxl.c
> > @@ -1086,7 +1086,7 @@ CXL_EXPORT unsigned long long cxl_cmd_identify_get_partition_align(
> >  	if (cmd->status < 0)
> >  		return cmd->status;
> >  
> > -	return le64_to_cpu(id->partition_align);
> > +	return le64_to_cpu(id->partition_align) * CXL_CAPACITY_MULTIPLIER;
> >  }
> >  
> >  CXL_EXPORT unsigned int cxl_cmd_identify_get_label_size(struct cxl_cmd *cmd)
> > -- 
> > 2.31.1
> >