Re: [PATCH v2 16/16] fwctl/cxl: Add documentation to FWCTL CXL

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

One minor comment.  With a sentence added on that (assuming I didn't miss
it somewhere)
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> diff --git a/Documentation/userspace-api/fwctl/fwctl-cxl.rst b/Documentation/userspace-api/fwctl/fwctl-cxl.rst
> new file mode 100644
> index 000000000000..8d9aeb77bc6d
> --- /dev/null
> +++ b/Documentation/userspace-api/fwctl/fwctl-cxl.rst
> @@ -0,0 +1,135 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +================
> +fwctl cxl driver
> +================
> +
> +:Author: Dave Jiang
> +
> +Overview
> +========
> +
> +The CXL spec defines a set of commands that can be issued to the mailbox of a
> +CXL device or switch. It also left room for vendor specific commands to be
> +issued to the mailbox as well. fwctl provides a path to issue a set of allowed
> +mailbox commands from user space to the device moderated by the kernel driver.
> +
> +The following 3 commands will be used to support CXL Features:
> +CXL spec r3.1 8.2.9.6.1 Get Supported Features (Opcode 0500h)
> +CXL spec r3.1 8.2.9.6.2 Get Feature (Opcode 0501h)
> +CXL spec r3.1 8.2.9.6.3 Set Feature (Opcode 0502h)
> +
> +The "Get Supported Features" return data may be filtered by the kernel driver to
> +drop any features that are forbidden by the kernel or being exclusively used by
> +the kernel. The "Get Supported Features" command and the "Get Features" falls
> +under the fwctl policy of FWCTL_RPC_CONFIGURATION.

Document what 'filtered' means given change to zero sized set?

> +
> +For "Set Feature" command, the access policy currently is broken down into two
> +categories depending on the Set Feature effects reported by the device. If the
> +Set Feature will cause immediate change to the device, the fwctl access policy
> +must be FWCTL_RPC_DEBUG_WRITE_FULL. The effects for this level are
> +"immediate config change", "immediate data change", "immediate policy change",
> +or "immediate log change" for the set effects mask. If the effects are "config
> +change with cold reset" or "config change with conventional reset", then the
> +fwctl access policy must be FWCTL_RPC_DEBUG_WRITE or higher.