linux-kernel - Re: [PATCH v10 2/4] PCI/DOE: Rename Discovery Response Data Object Contents to type

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Date: Thu, 23 May 2024 12:02:26 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Alistair Francis <alistair23@...il.com>
CC: <bhelgaas@...gle.com>, <linux-pci@...r.kernel.org>, <lukas@...ner.de>,
	<alex.williamson@...hat.com>, <christian.koenig@....com>, <kch@...dia.com>,
	<gregkh@...uxfoundation.org>, <logang@...tatee.com>,
	<linux-kernel@...r.kernel.org>, <chaitanyak@...dia.com>,
	<rdunlap@...radead.org>, Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v10 2/4] PCI/DOE: Rename Discovery Response Data Object
 Contents to type

On Wed, 22 May 2024 20:11:40 +1000
Alistair Francis <alistair23@...il.com> wrote:

> PCIe r6.1 (which was published July 24) describes a "Vendor ID", a
> "Data Object Type" and "Next Index" as the fields in the DOE
> Discovery Response Data Object. The DOE driver currently uses
> both the terms type and prot for the second element.
> 
> This patch renames all uses of the DOE Discovery Response Data Object
> to use type as the second element of the object header, instead of
> type/prot as it currently is.
> 
> Signed-off-by: Alistair Francis <alistair.francis@....com>

Other than the below query on it being a potentially breaking change
for userspace code this looks fine to me.

> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 94c00996e633..4fa1ec622177 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -1146,7 +1146,7 @@
>  #define PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX		0x000000ff
>  #define PCI_DOE_DATA_OBJECT_DISC_REQ_3_VER		0x0000ff00
>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_VID		0x0000ffff
> -#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL		0x00ff0000
> +#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE		0x00ff0000

Safe to change a userspace header?  I've no idea if any external project
is using this define but probably shouldn't make this change or should
leave a compatibility define in place.

>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX	0xff000000
>  
>  /* Compute Express Link (CXL r3.1, sec 8.1.5) */