Commit 8375e74f authored by Saravana Kannan's avatar Saravana Kannan Committed by Greg Kroah-Hartman
Browse files

driver core: Add fw_devlink kernel commandline option 



fwnode_operations.add_links allows creating device links from
information provided by firmware.

fwnode_operations.add_links is currently implemented only by
OF/devicetree code and a specific case of efi. However, there's nothing
preventing ACPI or other firmware types from implementing it.

The OF implementation is currently controlled by a kernel commandline
parameter called of_devlink.

Since this feature is generic isn't limited to OF, add a generic
fw_devlink kernel commandline parameter to control this feature across
firmware types.

Signed-off-by: default avatarSaravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200222014038.180923-3-saravanak@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1745d299

Documentation/admin-guide/kernel-parameters.txt

+18 −0
Original line number Diff line number Diff line
@@ -1350,6 +1350,24 @@ 
			can be changed at run time by the max_graph_depth file

			in the tracefs tracing directory. default: 0 (no limit)



	fw_devlink=	[KNL] Create device links between consumer and supplier

			devices by scanning the firmware to infer the

			consumer/supplier relationships. This feature is

			especially useful when drivers are loaded as modules as

			it ensures proper ordering of tasks like device probing

			(suppliers first, then consumers), supplier boot state

			clean up (only after all consumers have probed),

			suspend/resume & runtime PM (consumers first, then

			suppliers).

			Format: { off | permissive | on | rpm }

			off --	Don't create device links from firmware info.

			permissive -- Create device links from firmware info

				but use it only for ordering boot state clean

				up (sync_state() calls).

			on -- 	Create device links from firmware info and use it

				to enforce probe and suspend/resume ordering.

			rpm --	Like "on", but also use to order runtime PM.



	gamecon.map[2|3]=

			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad

			support via parallel port (up to 5 devices per port)

drivers/base/core.c

+26 −1
Original line number Diff line number Diff line
@@ -2332,6 +2332,31 @@ static int device_private_init(struct device *dev) 
	return 0;

}



u32 fw_devlink_flags;

static int __init fw_devlink_setup(char *arg)

{

	if (!arg)

		return -EINVAL;



	if (strcmp(arg, "off") == 0) {

		fw_devlink_flags = 0;

	} else if (strcmp(arg, "permissive") == 0) {

		fw_devlink_flags = DL_FLAG_SYNC_STATE_ONLY;

	} else if (strcmp(arg, "on") == 0) {

		fw_devlink_flags = DL_FLAG_AUTOPROBE_CONSUMER;

	} else if (strcmp(arg, "rpm") == 0) {

		fw_devlink_flags = DL_FLAG_AUTOPROBE_CONSUMER |

				   DL_FLAG_PM_RUNTIME;

	}

	return 0;

}

early_param("fw_devlink", fw_devlink_setup);



u32 fw_devlink_get_flags(void)

{

	return fw_devlink_flags;

}



/**

 * device_add - add device to device hierarchy.

 * @dev: device.
@@ -2480,7 +2505,7 @@ int device_add(struct device *dev) 
	 */

	device_link_add_missing_supplier_links();



	if (fwnode_has_op(dev->fwnode, add_links)) {

	if (fw_devlink_flags && fwnode_has_op(dev->fwnode, add_links)) {

		fw_ret = fwnode_call_int_op(dev->fwnode, add_links, dev);

		if (fw_ret == -ENODEV)

			device_link_wait_for_mandatory_supplier(dev);

include/linux/fwnode.h

+2 −0
Original line number Diff line number Diff line
@@ -170,4 +170,6 @@ struct fwnode_operations { 
	} while (false)

#define get_dev_from_fwnode(fwnode)	get_device((fwnode)->dev)



extern u32 fw_devlink_get_flags(void);



#endif

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