[RFC net-next 2/4] devlink: Add eswitch mode boot default

[Mark Bloch <mbloch@nvidia.com>]

Add support for configuring the devlink eswitch mode from the
devlink= kernel command line parameter.

The supported syntax is:

  devlink=[<handle>]:esw:mode:<mode>

where <mode> is one of legacy, switchdev or switchdev_inactive. The
default is applied through the existing eswitch_mode_set() devlink
operation, matching the userspace devlink eswitch set command.

Document the devlink= syntax and the eswitch mode default.

Signed-off-by: Mark Bloch <mbloch@nvidia.com>
---
 .../admin-guide/kernel-parameters.txt         |  24 ++++
 .../networking/devlink/devlink-defaults.rst   |  99 +++++++++++++++
 Documentation/networking/devlink/index.rst    |   1 +
 net/devlink/core.c                            | 114 ++++++++++++++++++
 4 files changed, 238 insertions(+)
 create mode 100644 Documentation/networking/devlink/devlink-defaults.rst

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 7834ee927310..150202882870 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1278,6 +1278,30 @@ Kernel parameters
 	dell_smm_hwmon.fan_max=
 			[HW] Maximum configurable fan speed.
 
+	devlink=	[NET]
+			Format:
+			<entry>[,<entry>...]
+
+			<entry>:
+			[<handle>[,<handle>...]]:<cmd>:<cmd-options>
+
+			<handle>:
+			<bus-name>/<dev-name>
+
+			Configure default devlink settings for matching
+			devlink instances during device initialization.
+
+			Currently supported settings:
+			esw:mode:{ legacy | switchdev | switchdev_inactive }
+
+			Examples:
+			devlink=[pci/0000:08:00.0]:esw:mode:switchdev
+			devlink=[pci/0000:08:00.0,pci/0000:08:00.1]:esw:mode:legacy
+			devlink=[pci/0000:08:00.0]:esw:mode:switchdev,[pci/0000:08:00.1]:esw:mode:switchdev_inactive
+
+			See Documentation/networking/devlink/devlink-defaults.rst
+			for the full syntax and duplicate handling rules.
+
 	dfltcc=		[HW,S390]
 			Format: { on | off | def_only | inf_only | always }
 			on:       s390 zlib hardware support for compression on
diff --git a/Documentation/networking/devlink/devlink-defaults.rst b/Documentation/networking/devlink/devlink-defaults.rst
new file mode 100644
index 000000000000..7d6ccaddca86
--- /dev/null
+++ b/Documentation/networking/devlink/devlink-defaults.rst
@@ -0,0 +1,99 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+================
+Devlink Defaults
+================
+
+Devlink defaults allow selected devlink settings to be provided on the
+kernel command line and applied to matching devlink instances during device
+initialization.
+
+The devlink device is selected by its devlink handle. For PCI devices this is
+the same handle shown by ``devlink dev show``, for example
+``pci/0000:08:00.0``.
+
+Kernel command line syntax
+==========================
+
+Defaults are specified with the ``devlink=`` kernel command line parameter.
+
+The general syntax is::
+
+  devlink=<default>[,<default>...]
+
+Each default has the following form::
+
+  [<handle-list>]:<cmd>:<cmd-options>
+
+``<handle-list>`` is one or more devlink handles::
+
+  <bus-name>/<dev-name>[,<bus-name>/<dev-name>...]
+
+All handles in the same ``[]`` list receive the same command setting.
+
+Multiple defaults may be specified by separating complete defaults with a
+comma after the value::
+
+  devlink=[pci/0000:08:00.0]:esw:mode:switchdev,[pci/0000:08:00.1]:esw:mode:legacy
+
+Syntax rules
+------------
+
+The following syntax rules apply:
+
+* Specify all defaults in one ``devlink=`` parameter. Repeated ``devlink=``
+  parameters are not accumulated.
+* The ``devlink=`` value is limited by the kernel command line size.
+* Whitespace is not allowed within the parameter value.
+* ``<bus-name>`` and ``<dev-name>`` must not be empty.
+* ``<bus-name>`` must not contain ``:``.
+* ``<dev-name>`` may contain ``:``. This allows PCI names such as
+  ``0000:08:00.0``.
+* Handles must not contain whitespace, ``[``, ``]`` or more than one ``/``.
+* A comma inside ``[]`` separates handles.
+* A comma after the ``<value>`` separates defaults.
+* Defaults for the same handle are applied in command-line order.
+* The same ``esw`` attribute may be specified only once for a given devlink
+  handle.
+* Duplicate entries for the same handle are rejected and all devlink defaults
+  are ignored.
+
+Supported defaults
+==================
+
+The supported command is ``esw``:
+
+.. list-table::
+   :widths: 10 25 35
+   :header-rows: 1
+
+   * - Command
+     - Options
+     - Values
+   * - ``esw``
+     - ``mode:<mode>``
+     - ``legacy``, ``switchdev``, ``switchdev_inactive``
+
+The ``esw:mode`` default corresponds to the userspace command::
+
+  devlink dev eswitch set <handle> mode <value>
+
+
+Examples
+========
+
+Set one PCI devlink instance to switchdev mode::
+
+  devlink=[pci/0000:08:00.0]:esw:mode:switchdev
+
+Set two PCI devlink instances to legacy mode::
+
+  devlink=[pci/0000:08:00.0,pci/0000:08:00.1]:esw:mode:legacy
+
+Set different modes for different PCI devlink instances::
+
+  devlink=[pci/0000:08:00.0]:esw:mode:switchdev,[pci/0000:08:00.1]:esw:mode:switchdev_inactive
+
+The following is invalid because the same handle receives ``esw:mode`` twice::
+
+  devlink=[pci/0000:08:00.0]:esw:mode:legacy,[pci/0000:08:00.0]:esw:mode:switchdev
diff --git a/Documentation/networking/devlink/index.rst b/Documentation/networking/devlink/index.rst
index f7ba7dcf477d..0d27a7008b14 100644
--- a/Documentation/networking/devlink/index.rst
+++ b/Documentation/networking/devlink/index.rst
@@ -56,6 +56,7 @@ general.
    :maxdepth: 1
 
    devlink-dpipe
+   devlink-defaults
    devlink-eswitch-attr
    devlink-flash
    devlink-health
diff --git a/net/devlink/core.c b/net/devlink/core.c
index 2421a1f8dbb7..4b404135181c 100644
--- a/net/devlink/core.c
+++ b/net/devlink/core.c
@@ -73,9 +73,123 @@ devlink_default_attr_free(struct devlink_default_attr_item *attr)
 	kfree(attr->value.param.value);
 }
 
+struct devlink_default_attr_spec {
+	const char *name;
+	enum devlink_attr attr;
+	int (*value_parse)(const char *value,
+			   struct devlink_default_attr_item *attr_item);
+};
+
+static int __init
+devlink_default_attr_parse(char *str,
+			   const struct devlink_default_attr_spec *attrs,
+			   size_t attrs_count,
+			   struct devlink_default_attr_item *attr_item)
+{
+	char *attr_name;
+	char *value;
+	size_t i;
+
+	attr_name = strsep(&str, ":");
+	if (!attr_name || !*attr_name || !str || !*str)
+		return -EINVAL;
+
+	value = str;
+	for (i = 0; i < attrs_count; i++) {
+		if (!strcmp(attr_name, attrs[i].name)) {
+			attr_item->attr = attrs[i].attr;
+			return attrs[i].value_parse(value, attr_item);
+		}
+	}
+
+	return -EINVAL;
+}
+
+static int __init
+devlink_default_esw_mode_to_value(const char *str,
+				  enum devlink_eswitch_mode *mode)
+{
+	if (!strcmp(str, "legacy")) {
+		*mode = DEVLINK_ESWITCH_MODE_LEGACY;
+		return 0;
+	}
+	if (!strcmp(str, "switchdev")) {
+		*mode = DEVLINK_ESWITCH_MODE_SWITCHDEV;
+		return 0;
+	}
+	if (!strcmp(str, "switchdev_inactive")) {
+		*mode = DEVLINK_ESWITCH_MODE_SWITCHDEV_INACTIVE;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int __init
+devlink_default_esw_mode_parse(const char *str,
+			       struct devlink_default_attr_item *attr_item)
+{
+	enum devlink_eswitch_mode mode;
+	int err;
+
+	err = devlink_default_esw_mode_to_value(str, &mode);
+	if (err)
+		return err;
+
+	attr_item->value.eswitch_mode = mode;
+	return 0;
+}
+
+static const struct devlink_default_attr_spec devlink_default_esw_attrs[] __initconst = {
+	{ "mode", DEVLINK_ATTR_ESWITCH_MODE, devlink_default_esw_mode_parse },
+};
+
+static int __init
+devlink_default_esw_attr_parse(char *str,
+			       struct devlink_default_attr_item *attr_item)
+{
+	return devlink_default_attr_parse(str, devlink_default_esw_attrs,
+					  ARRAY_SIZE(devlink_default_esw_attrs),
+					  attr_item);
+}
+
+static int
+devlink_default_eswitch_apply(struct devlink *devlink,
+			      const struct devlink_default_attr_item *attr)
+{
+	const struct devlink_ops *ops = devlink->ops;
+
+	switch (attr->attr) {
+	case DEVLINK_ATTR_ESWITCH_MODE:
+		if (!ops->eswitch_mode_set)
+			return -EOPNOTSUPP;
+
+		return ops->eswitch_mode_set(devlink, attr->value.eswitch_mode,
+					     NULL);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static const struct devlink_default_cmd_spec devlink_default_cmds[] __initconst = {
+	{
+		.name = "esw",
+		.cmd = DEVLINK_CMD_ESWITCH_SET,
+		.run = devlink_default_eswitch_apply,
+		.attr_parse = devlink_default_esw_attr_parse,
+	},
+};
+
 static const struct devlink_default_cmd_spec *__init
 devlink_default_cmd_spec_find(const char *name)
 {
+	size_t i;
+
+	for (i = 0; i < ARRAY_SIZE(devlink_default_cmds); i++) {
+		if (!strcmp(name, devlink_default_cmds[i].name))
+			return &devlink_default_cmds[i];
+	}
+
 	return NULL;
 }
 
-- 
2.34.1