Commit 0858caa4 authored by David Howells's avatar David Howells
Browse files

uapi: General notification queue definitions 



Add UAPI definitions for the general notification queue, including the
following pieces:

 (*) struct watch_notification.

     This is the metadata header for notification messages.  It includes a
     type and subtype that indicate the source of the message
     (eg. WATCH_TYPE_MOUNT_NOTIFY) and the kind of the message
     (eg. NOTIFY_MOUNT_NEW_MOUNT).

     The header also contains an information field that conveys the
     following information:

	- WATCH_INFO_LENGTH.  The size of the entry (entries are variable
          length).

	- WATCH_INFO_ID.  The watch ID specified when the watchpoint was
          set.

	- WATCH_INFO_TYPE_INFO.  (Sub)type-specific information.

	- WATCH_INFO_FLAG_*.  Flag bits overlain on the type-specific
          information.  For use by the type.

     All the information in the header can be used in filtering messages at
     the point of writing into the buffer.

 (*) struct watch_notification_removal

     This is an extended watch-removal notification record that includes an
     'id' field that can indicate the identifier of the object being
     removed if available (for instance, a keyring serial number).

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent b9bbe6ed

include/uapi/linux/watch_queue.h

0 → 100644
+55 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

#ifndef _UAPI_LINUX_WATCH_QUEUE_H

#define _UAPI_LINUX_WATCH_QUEUE_H



#include <linux/types.h>



enum watch_notification_type {

	WATCH_TYPE_META		= 0,	/* Special record */

	WATCH_TYPE__NR		= 1

};



enum watch_meta_notification_subtype {

	WATCH_META_REMOVAL_NOTIFICATION	= 0,	/* Watched object was removed */

	WATCH_META_LOSS_NOTIFICATION	= 1,	/* Data loss occurred */

};



/*

 * Notification record header.  This is aligned to 64-bits so that subclasses

 * can contain __u64 fields.

 */

struct watch_notification {

	__u32			type:24;	/* enum watch_notification_type */

	__u32			subtype:8;	/* Type-specific subtype (filterable) */

	__u32			info;

#define WATCH_INFO_LENGTH	0x0000007f	/* Length of record */

#define WATCH_INFO_LENGTH__SHIFT 0

#define WATCH_INFO_ID		0x0000ff00	/* ID of watchpoint */

#define WATCH_INFO_ID__SHIFT	8

#define WATCH_INFO_TYPE_INFO	0xffff0000	/* Type-specific info */

#define WATCH_INFO_TYPE_INFO__SHIFT 16

#define WATCH_INFO_FLAG_0	0x00010000	/* Type-specific info, flag bit 0 */

#define WATCH_INFO_FLAG_1	0x00020000	/* ... */

#define WATCH_INFO_FLAG_2	0x00040000

#define WATCH_INFO_FLAG_3	0x00080000

#define WATCH_INFO_FLAG_4	0x00100000

#define WATCH_INFO_FLAG_5	0x00200000

#define WATCH_INFO_FLAG_6	0x00400000

#define WATCH_INFO_FLAG_7	0x00800000

};





/*

 * Extended watch removal notification.  This is used optionally if the type

 * wants to indicate an identifier for the object being watched, if there is

 * such.  This can be distinguished by the length.

 *

 * type -> WATCH_TYPE_META

 * subtype -> WATCH_META_REMOVAL_NOTIFICATION

 */

struct watch_notification_removal {

	struct watch_notification watch;

	__u64	id;		/* Type-dependent identifier */

};



#endif /* _UAPI_LINUX_WATCH_QUEUE_H */

CRA Git | Maintained and supported by SUSTech CRA and CCSE