Re: [PATCH v3 16/28] cxl/mbox: Introduce the mbox_send operation

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

On Tue, 24 Aug 2021 09:06:52 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> In preparation for implementing a unit test backend transport for ioctl
> operations, and making the mailbox available to the cxl/pmem
> infrastructure, move the existing PCI specific portion of mailbox handling
> to an "mbox_send" operation.
> 
> With this split all the PCI-specific transport details are comprehended
> by a single operation and the rest of the mailbox infrastructure is
> 'struct cxl_mem' and 'struct cxl_memdev' generic.
> 
> Acked-by: Ben Widawsky <ben.widawsky@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/cxl/cxlmem.h |   42 ++++++++++++++++++++++++++++
>  drivers/cxl/pci.c    |   76 ++++++++++++++------------------------------------
>  2 files changed, 63 insertions(+), 55 deletions(-)
> 
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 8397daea9d9b..a56d8f26a157 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -66,6 +66,45 @@ struct cxl_memdev *
>  devm_cxl_add_memdev(struct device *host, struct cxl_mem *cxlm,
>  		    const struct cdevm_file_operations *cdevm_fops);
>  
> +/**
> + * struct mbox_cmd - A command to be submitted to hardware.

struct cxl_mbox_cmd

> + * @opcode: (input) The command set and command submitted to hardware.
> + * @payload_in: (input) Pointer to the input payload.
> + * @payload_out: (output) Pointer to the output payload. Must be allocated by
> + *		 the caller.
> + * @size_in: (input) Number of bytes to load from @payload_in.
> + * @size_out: (input) Max number of bytes loaded into @payload_out.
> + *            (output) Number of bytes generated by the device. For fixed size
> + *            outputs commands this is always expected to be deterministic. For
> + *            variable sized output commands, it tells the exact number of bytes
> + *            written.
> + * @return_code: (output) Error code returned from hardware.
> + *
> + * This is the primary mechanism used to send commands to the hardware.
> + * All the fields except @payload_* correspond exactly to the fields described in
> + * Command Register section of the CXL 2.0 8.2.8.4.5. @payload_in and
> + * @payload_out are written to, and read from the Command Payload Registers
> + * defined in CXL 2.0 8.2.8.4.8.
> + */
> +struct cxl_mbox_cmd {
> +	u16 opcode;
> +	void *payload_in;
> +	void *payload_out;
> +	size_t size_in;
> +	size_t size_out;
> +	u16 return_code;
> +#define CXL_MBOX_SUCCESS 0
> +};