Re: [PATCH net-next v8 1/2] net: Add a WWAN subsystem

Greg KH
2021-04-02T14:03:00Z

On Fri, Apr 02, 2021 at 04:06:36PM +0200, Loic Poulain wrote:
> This change introduces initial support for a WWAN framework. Given the
> complexity and heterogeneity of existing WWAN hardwares and interfaces,
> there is no strict definition of what a WWAN device is and how it should
> be represented. It's often a collection of multiple devices that perform
> the global WWAN feature (netdev, tty, chardev, etc).
>
> One usual way to expose modem controls and configuration is via high
> level protocols such as the well known AT command protocol, MBIM or
> QMI. The USB modems started to expose that as character devices, and
> user daemons such as ModemManager learnt how to deal with them. This
> initial version adds the concept of WWAN port, which can be created
> by any driver to expose one of these protocols. The WWAN core takes
> care of the generic part, including character device management, and
> rely on port operations to received and submit protocol data.
>
> Since the different components/devices do no necesserarly know about
> each others, and can be created/removed in different orders, the
> WWAN core ensures that all WAN ports that contribute to the 'whole'
> WWAN feature are grouped under the same virtual WWAN device, relying
> on the provided parent device (e.g. mhi controller, USB device). It's
> a 'trick' I copied from Johannes's earlier WWAN subsystem proposal.
>
> This initial version is purposely minimalist, it's essentially moving
> the generic part of the previously proposed mhi_wwan_ctrl driver inside
> a common WWAN framework, but the implementation is open and flexible
> enough to allow extension for further drivers.
>
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

Always run checkpatch before sending stuff off :(

Anyway, one thing did stand out:

> --- /dev/null
> +++ b/include/linux/wwan.h
> @@ -0,0 +1,127 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
> +
> +#ifndef __WWAN_H
> +#define __WWAN_H
> +
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/skbuff.h>
> +
> +/**
> + * enum wwan_port_type - WWAN port types
> + * @WWAN_PORT_AT: AT commands
> + * @WWAN_PORT_MBIM: Mobile Broadband Interface Model control
> + * @WWAN_PORT_QMI: Qcom modem/MSM interface for modem control
> + * @WWAN_PORT_QCDM: Qcom Modem diagnostic interface
> + * @WWAN_PORT_FIREHOSE: XML based command protocol
> + * @WWAN_PORT_MAX
> + */
> +enum wwan_port_type {
> + WWAN_PORT_AT,
> + WWAN_PORT_MBIM,
> + WWAN_PORT_QMI,
> + WWAN_PORT_QCDM,
> + WWAN_PORT_FIREHOSE,
> + WWAN_PORT_MAX,
> +};
> +
> +/**
> + * struct wwan_port - The structure that defines a WWAN port
> + * @type: Port type
> + * @start_count: Port start counter
> + * @flags: Store port state and capabilities
> + * @ops: Pointer to WWAN port operations
> + * @ops_lock: Protect port ops
> + * @dev: Underlying device
> + * @rxq: Buffer inbound queue
> + * @waitqueue: The waitqueue for port fops (read/write/poll)
> + */
> +struct wwan_port {
> + enum wwan_port_type type;
> + unsigned int start_count;
> + unsigned long flags;
> + const struct wwan_port_ops *ops;
> + struct mutex ops_lock;
> + struct device dev;
> + struct sk_buff_head rxq;
> + wait_queue_head_t waitqueue;
> +};

No need to put the actual definition of struct wwan_port in this .h
file, keep it private in your .c file to keep wwan drivers from poking
around in it where they shouldn't be :)

thanks,

greg k-h