Subject: Re: [patch net-next v2 02/10] net: introduce generic switch devices support

From: Roopa Prabhu <[email-masked]>
Date: Wed, 19 Nov 2014 05:28:10 -0800

On 11/9/14, 2:51 AM, Jiri Pirko wrote:
> The goal of this is to provide a possibility to support various switch
> chips. Drivers should implement relevant ndos to do so. Now there is
> only one ndo defined:
> - for getting physical switch id is in place.
>
> Note that user can use random port netdevice to access the switch.
>
> Signed-off-by: Jiri Pirko <[email-masked]>
> ---
>   Documentation/networking/switchdev.txt | 59 ++++++++++++++++++++++++++++++++++
>   MAINTAINERS                            |  7 ++++
>   include/linux/netdevice.h              | 10 ++++++
>   include/net/switchdev.h                | 30 +++++++++++++++++
>   net/Kconfig                            |  1 +
>   net/Makefile                           |  3 ++
>   net/switchdev/Kconfig                  | 13 ++++++++
>   net/switchdev/Makefile                 |  5 +++
>   net/switchdev/switchdev.c              | 33 +++++++++++++++++++
>   9 files changed, 161 insertions(+)
>   create mode 100644 Documentation/networking/switchdev.txt
>   create mode 100644 include/net/switchdev.h
>   create mode 100644 net/switchdev/Kconfig
>   create mode 100644 net/switchdev/Makefile
>   create mode 100644 net/switchdev/switchdev.c
>
> diff --git a/Documentation/networking/switchdev.txt b/Documentation/networking/switchdev.txt
> new file mode 100644
> index 0000000..98be76c
> --- /dev/null
> +++ b/Documentation/networking/switchdev.txt
> @@ -0,0 +1,59 @@
> +Switch (and switch-ish) device drivers HOWTO
> +===========================
> +
> +Please note that the word "switch" is here used in very generic meaning.
> +This include devices supporting L2/L3 but also various flow offloading chips,
> +including switches embedded into SR-IOV NICs.
> +
> +Lets describe a topology a bit. Imagine the following example:
> +
> +       +----------------------------+    +---------------+
> +       |     SOME switch chip       |    |      CPU      |
> +       +----------------------------+    +---------------+
> +       port1 port2 port3 port4 MNGMNT    |     PCI-E     |
> +         |     |     |     |     |       +---------------+
> +        PHY   PHY    |     |     |         |  NIC0 NIC1
> +                     |     |     |         |   |    |
> +                     |     |     +- PCI-E -+   |    |
> +                     |     +------- MII -------+    |
> +                     +------------- MII ------------+
> +
> +In this example, there are two independent lines between the switch silicon
> +and CPU. NIC0 and NIC1 drivers are not aware of a switch presence. They are
> +separate from the switch driver. SOME switch chip is by managed by a driver
> +via PCI-E device MNGMNT. Note that MNGMNT device, NIC0 and NIC1 may be
> +connected to some other type of bus.
> +
> +Now, for the previous example show the representation in kernel:
> +
> +       +----------------------------+    +---------------+
> +       |     SOME switch chip       |    |      CPU      |
> +       +----------------------------+    +---------------+
> +       sw0p0 sw0p1 sw0p2 sw0p3 MNGMNT    |     PCI-E     |
> +         |     |     |     |     |       +---------------+
> +        PHY   PHY    |     |     |         |  eth0 eth1
> +                     |     |     |         |   |    |
> +                     |     |     +- PCI-E -+   |    |
> +                     |     +------- MII -------+    |
> +                     +------------- MII ------------+
> +
> +Lets call the example switch driver for SOME switch chip "SOMEswitch". This
> +driver takes care of PCI-E device MNGMNT. There is a netdevice instance sw0pX
> +created for each port of a switch. These netdevices are instances
> +of "SOMEswitch" driver. sw0pX netdevices serve as a "representation"
> +of the switch chip. eth0 and eth1 are instances of some other existing driver.
> +
> +The only difference of the switch-port netdevice from the ordinary netdevice
> +is that is implements couple more NDOs:
> +
> +	ndo_sw_parent_get_id - This returns the same ID for two port netdevices
> +			       of the same physical switch chip. This is
> +			       mandatory to be implemented by all switch drivers
> +			       and serves the caller for recognition of a port
> +			       netdevice.
> +	ndo_sw_parent_* - Functions that serve for a manipulation of the switch
> +			  chip itself (it can be though of as a "parent" of the
> +			  port, therefore the name). They are not port-specific.
> +			  Caller might use arbitrary port netdevice of the same
> +			  switch and it will make no difference.
> +	ndo_sw_port_* - Functions that serve for a port-specific manipulation.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3a41fb0..776e078 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9003,6 +9003,13 @@ F:	lib/swiotlb.c
>   F:	arch/*/kernel/pci-swiotlb.c
>   F:	include/linux/swiotlb.h
>   
> +SWITCHDEV
> +M:	Jiri Pirko <[email-masked]>
> +L:	[email-masked]
> +S:	Supported
> +F:	net/switchdev/
> +F:	include/net/switchdev.h
> +
>   SYNOPSYS ARC ARCHITECTURE
>   M:	Vineet Gupta <[email-masked]>
>   S:	Supported
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 71922e0..97eade9 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1017,6 +1017,12 @@ typedef u16 (*select_queue_fallback_t)(struct net_device *dev,
>    *	performing GSO on a packet. The device returns true if it is
>    *	able to GSO the packet, false otherwise. If the return value is
>    *	false the stack will do software GSO.
> + *
> + * int (*ndo_sw_parent_id_get)(struct net_device *dev,
> + *			       struct netdev_phys_item_id *psid);
> + *	Called to get an ID of the switch chip this port is part of.
> + *	If driver implements this, it indicates that it represents a port
> + *	of a switch chip.
>    */
>   struct net_device_ops {
>   	int			(*ndo_init)(struct net_device *dev);
> @@ -1168,6 +1174,10 @@ struct net_device_ops {
>   	int			(*ndo_get_lock_subclass)(struct net_device *dev);
>   	bool			(*ndo_gso_check) (struct sk_buff *skb,
>   						  struct net_device *dev);
> +#ifdef CONFIG_NET_SWITCHDEV
> +	int			(*ndo_sw_parent_id_get)(struct net_device *dev,
> +							struct netdev_phys_item_id *psid);
Can we keep the name generic and not include "sw" which implies switch 
here ?.
I understand that it is under CONFIG_NET_SWITCHDEV but we might find use 
for them in other offload scenarios in the future.
This particular ndo can be just ndo_parent_id_get().
And the others that do specific offloads can have "offload" in them if 
required..?.

> +#endif
>   };
>   
>   /**
> diff --git a/include/net/switchdev.h b/include/net/switchdev.h
> new file mode 100644
> index 0000000..79bf9bd
> --- /dev/null
> +++ b/include/net/switchdev.h
> @@ -0,0 +1,30 @@
> +/*
> + * include/net/switchdev.h - Switch device API
> + * Copyright (c) 2014 Jiri Pirko <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +#ifndef _LINUX_SWITCHDEV_H_
> +#define _LINUX_SWITCHDEV_H_
> +
> +#include <linux/netdevice.h>
> +
> +#ifdef CONFIG_NET_SWITCHDEV
> +
> +int netdev_sw_parent_id_get(struct net_device *dev,
> +			    struct netdev_phys_item_id *psid);
> +
> +#else
> +
> +static inline int netdev_sw_parent_id_get(struct net_device *dev,
> +					  struct netdev_phys_item_id *psid)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +#endif
> +
> +#endif /* _LINUX_SWITCHDEV_H_ */
> diff --git a/net/Kconfig b/net/Kconfig
> index 99815b5..ff9ffc1 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -228,6 +228,7 @@ source "net/vmw_vsock/Kconfig"
>   source "net/netlink/Kconfig"
>   source "net/mpls/Kconfig"
>   source "net/hsr/Kconfig"
> +source "net/switchdev/Kconfig"
>   
>   config RPS
>   	boolean
> diff --git a/net/Makefile b/net/Makefile
> index 7ed1970..95fc694 100644
> --- a/net/Makefile
> +++ b/net/Makefile
> @@ -73,3 +73,6 @@ obj-$(CONFIG_OPENVSWITCH)	+= openvswitch/
>   obj-$(CONFIG_VSOCKETS)	+= vmw_vsock/
>   obj-$(CONFIG_NET_MPLS_GSO)	+= mpls/
>   obj-$(CONFIG_HSR)		+= hsr/
> +ifneq ($(CONFIG_NET_SWITCHDEV),)
> +obj-y				+= switchdev/
> +endif
> diff --git a/net/switchdev/Kconfig b/net/switchdev/Kconfig
> new file mode 100644
> index 0000000..1557545
> --- /dev/null
> +++ b/net/switchdev/Kconfig
> @@ -0,0 +1,13 @@
> +#
> +# Configuration for Switch device support
> +#
> +
> +config NET_SWITCHDEV
> +	boolean "Switch (and switch-ish) device support (EXPERIMENTAL)"
> +	depends on INET
> +	---help---
> +	  This module provides glue between core networking code and device
> +	  drivers in order to support hardware switch chips in very generic
> +	  meaning of the word "switch". This include devices supporting L2/L3 but
> +	  also various flow offloading chips, including switches embedded into
> +	  SR-IOV NICs.
> diff --git a/net/switchdev/Makefile b/net/switchdev/Makefile
> new file mode 100644
> index 0000000..5ed63ed
> --- /dev/null
> +++ b/net/switchdev/Makefile
> @@ -0,0 +1,5 @@
> +#
> +# Makefile for the Switch device API
> +#
> +
> +obj-$(CONFIG_NET_SWITCHDEV) += switchdev.o
> diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
> new file mode 100644
> index 0000000..5010f646
> --- /dev/null
> +++ b/net/switchdev/switchdev.c
> @@ -0,0 +1,33 @@
> +/*
> + * net/switchdev/switchdev.c - Switch device API
> + * Copyright (c) 2014 Jiri Pirko <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <linux/init.h>
> +#include <linux/netdevice.h>
> +#include <net/switchdev.h>
> +
> +/**
> + *	netdev_sw_parent_id_get - Get ID of a switch
> + *	@dev: port device
> + *	@psid: switch ID
> + *
> + *	Get ID of a switch this port is part of.
> + */
> +int netdev_sw_parent_id_get(struct net_device *dev,
> +			    struct netdev_phys_item_id *psid)
> +{
> +	const struct net_device_ops *ops = dev->netdev_ops;
> +
> +	if (!ops->ndo_sw_parent_id_get)
> +		return -EOPNOTSUPP;
> +	return ops->ndo_sw_parent_id_get(dev, psid);
> +}
> +EXPORT_SYMBOL(netdev_sw_parent_id_get);