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From: Dan Williams <>
To: Ben Widawsky <>
	Jonathan Cameron <>,
	Alison Schofield <>,
	Ira Weiny <>,
	Vishal Verma <>
Subject: Re: [PATCH v2] cxl: Rename mem to pci
Date: Thu, 20 May 2021 12:39:21 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, May 20, 2021 at 11:41 AM Ben Widawsky <> wrote:
> As the driver has undergone development, it's become clear that the
> majority [entirety?] of the current functionality in mem.c is actually a
> layer encapsulating functionality exposed through PCI based
> interactions. This layer can be used either in isolation or to provide
> functionality for higher level functionality.
> CXL capabilities exist in a parallel domain to PCIe. CXL devices are
> enumerable and controllable via "legacy" PCIe mechanisms; however, their
> CXL capabilities are a superset of PCIe. For example, a CXL device may
> be connected to a non-CXL capable PCIe root port, and therefore will not
> be able to participate in CXL.mem or CXL.cache operations, but can still
> be accessed through PCIe mechanisms for operations.
> To properly represent the PCI nature of this driver, and in preparation for
> introducing a new driver for the CXL.mem / HDM decoder (Host-managed Device
> Memory) capabilities of a CXL memory expander, rename mem.c to pci.c so that
> mem.c is available for this new driver.
> The result of the change is that there is a clear layering distinction
> in the driver, and a systems administrator may load only the cxl_pci
> module and gain access to such operations as, firmware update, offline
> provisioning of devices, and error collection. In addition to freeing up
> the file name for another purpose, there are two primary reasons this is
> useful,
>     1. Acting upon devices which don't have full CXL capabilities. This
>        may happen for instance if the CXL device is connected in a CXL
>        unaware part of the platform topology.
>     2. Userspace-first provisioning for devices without kernel driver
>        interference. This may be useful when provisioning a new device
>        in a specific manner that might otherwise be blocked or prevented
>        by the real CXL mem driver.
> Signed-off-by: Ben Widawsky <>
> ---
> v2: Makes it clear that the main motivation for this patch is for proper
> layering and that administrative PCI-only activities is a secondary benefit.
> I'm proposing we take the hit now and merge this as our next patch for cxl/next.

Looks good to me, and I think low risk to expedite into cxl/next to
remove the burden on git to cope with other development touching these

Reviewed-by: Dan Williams <>

  reply	other threads:[~2021-05-20 19:39 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-04 18:57 [PATCH] cxl: Rename mem to pci Ben Widawsky
2021-05-10 17:29 ` Jonathan Cameron
2021-05-20 18:41   ` [PATCH v2] " Ben Widawsky
2021-05-20 19:39     ` Dan Williams [this message]
2021-05-26 17:44       ` [PATCH v3] " Ben Widawsky
2021-05-26 18:01         ` Ben Widawsky

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