linux-kernel - Re: [PATCH RFC 2/2] cxl/memdev: Remove temporary variables from cxl_memdev

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Message-ID: <679a582927d8b_1e2dd62943e@iweiny-mobl.notmuch>
Date: Wed, 29 Jan 2025 10:32:41 -0600
From: Ira Weiny <ira.weiny@...el.com>
To: Alejandro Lucero Palau <alucerop@....com>, Ira Weiny
	<ira.weiny@...el.com>, Dave Jiang <dave.jiang@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Davidlohr Bueso <dave@...olabs.net>, "Jonathan
 Cameron" <jonathan.cameron@...wei.com>, Alison Schofield
	<alison.schofield@...el.com>, Vishal Verma <vishal.l.verma@...el.com>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 2/2] cxl/memdev: Remove temporary variables from
 cxl_memdev_state

Alejandro Lucero Palau wrote:
> 
> On 1/28/25 18:51, Ira Weiny wrote:
> > As was mentioned by Dan[1] cxl_memdev_state stores values which are only
> > used during device probe.  This clutters the data structure and is a
> > hindrance on code maintenance.  Those values are best handled with
> > temporary variables.
> >
> > Adjust the query of memory devices to read byte sizes in one call which
> > takes partition information into account.  Use the values to create
> > partitions for device state initialization.  Take care to separate the
> > mailbox queries from the initialization of device state to steer the
> > mbox code toward taking mailbox objects rather than memdev states.
> > Update spec references while changing these calls.
> >
> > Link: https://lore.kernel.org/all/67871f05cd767_20f32947f@dwillia2-xfh.jf.intel.com.notmuch/ [1]
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> 
> 
> Reviewed-by: Alejandro Lucero <alucerop@....com>
> 
> 
> FWIW, I had (as part of current in-progress v10) similar struct than 
> used here for Type2 initialization when there is no mailbox.
> 
> 
> I had added a specific function for initialising that struct, but my 
> idea now with this change is to have cxl_mem_dev_info initialized by the 
> driver before calling cxl_dev_state_identify,

Why is the accelerator calling cxl_dev_state_identify?  I did not see that
in v9.  My idea was that was a mailbox only call which is only needed for
memdevs.  And cxl_add_partition() can be called by accelerators as a
convenience function to aid in creating cxl_dpa_info.  (This and cxl_test
needed that function shared so it just got left in mbox.c)

> and inside that function 

I'm not clear which 'that function' you are referring to here.

> checking if total_bytes already != 0 for avoiding call the mbox command 
> for getting the info. This will support both cases for Type2, with and 
> without mailbox.

I think I agree with you except the != 0 to avoid mailbox commands.

Unless I am miss-understanding Dan we need to get to a place where mailbox
commands stop filling in structures unless those work for both type 2 and
3 __and__ are optional.  Because putting in special checks for the type
within a cxl/core/mailbox call is wrong IMO.

Ira