linux-kernel - Re: [PATCH v6 07/10] cxl/pci: Split cxl_pci_setup

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Date:   Wed, 10 Nov 2021 17:14:37 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     <linux-cxl@...r.kernel.org>, Ben Widawsky <ben.widawsky@...el.com>,
        "Ira Weiny" <ira.weiny@...el.com>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 07/10] cxl/pci: Split cxl_pci_setup_regs()

On Fri, 15 Oct 2021 16:30:42 -0700
Dan Williams <dan.j.williams@...el.com> wrote:

> From: Ben Widawsky <ben.widawsky@...el.com>
> 
> In preparation for moving parts of register mapping to cxl_core, split
> cxl_pci_setup_regs() into a helper that finds register blocks,
> (cxl_find_regblock()), and a generic wrapper that probes the precise
> register sets within a block (cxl_setup_regs()).
> 
> Move the actual mapping (cxl_map_regs()) of the only register-set that
> cxl_pci cares about (memory device registers) up a level from the former
> cxl_pci_setup_regs() into cxl_pci_probe().
> 
> With this change the unused component registers are no longer mapped,
> but the helpers are primed to move into the core.
> 
> [djbw: drop cxl_map_regs() for component registers]
> 
> Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
> [djbw: rebase on the cxl_register_map refactor]
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Hi Ben / all,

This is probably the best patch to comment on for this
(note it is not a comment about this patch, but more the state we end up
in after it).

cxl_map_regs() is a generic function, but with the new split approach
as a result of this patch, we now always know at the caller which of
the types of map we are doing.

I think it would be clearer to embrace that situation and drop cxl_map_regs()
in favor of directly calling the relevant specific versions such as
cxl_map_device_regs().  I can't immediately see how the generic cxl_map_regs()
will be useful to us going forwards.

Jonathan