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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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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: David Howells <dhowells@redhat.com>

David Howells 0858caa4 b9bbe6ed

+55
+55
include/uapi/linux/watch_queue.h
··· 1 + /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ 2 + #ifndef _UAPI_LINUX_WATCH_QUEUE_H 3 + #define _UAPI_LINUX_WATCH_QUEUE_H 4 + 5 + #include <linux/types.h> 6 + 7 + enum watch_notification_type { 8 + WATCH_TYPE_META = 0, /* Special record */ 9 + WATCH_TYPE__NR = 1 10 + }; 11 + 12 + enum watch_meta_notification_subtype { 13 + WATCH_META_REMOVAL_NOTIFICATION = 0, /* Watched object was removed */ 14 + WATCH_META_LOSS_NOTIFICATION = 1, /* Data loss occurred */ 15 + }; 16 + 17 + /* 18 + * Notification record header. This is aligned to 64-bits so that subclasses 19 + * can contain __u64 fields. 20 + */ 21 + struct watch_notification { 22 + __u32 type:24; /* enum watch_notification_type */ 23 + __u32 subtype:8; /* Type-specific subtype (filterable) */ 24 + __u32 info; 25 + #define WATCH_INFO_LENGTH 0x0000007f /* Length of record */ 26 + #define WATCH_INFO_LENGTH__SHIFT 0 27 + #define WATCH_INFO_ID 0x0000ff00 /* ID of watchpoint */ 28 + #define WATCH_INFO_ID__SHIFT 8 29 + #define WATCH_INFO_TYPE_INFO 0xffff0000 /* Type-specific info */ 30 + #define WATCH_INFO_TYPE_INFO__SHIFT 16 31 + #define WATCH_INFO_FLAG_0 0x00010000 /* Type-specific info, flag bit 0 */ 32 + #define WATCH_INFO_FLAG_1 0x00020000 /* ... */ 33 + #define WATCH_INFO_FLAG_2 0x00040000 34 + #define WATCH_INFO_FLAG_3 0x00080000 35 + #define WATCH_INFO_FLAG_4 0x00100000 36 + #define WATCH_INFO_FLAG_5 0x00200000 37 + #define WATCH_INFO_FLAG_6 0x00400000 38 + #define WATCH_INFO_FLAG_7 0x00800000 39 + }; 40 + 41 + 42 + /* 43 + * Extended watch removal notification. This is used optionally if the type 44 + * wants to indicate an identifier for the object being watched, if there is 45 + * such. This can be distinguished by the length. 46 + * 47 + * type -> WATCH_TYPE_META 48 + * subtype -> WATCH_META_REMOVAL_NOTIFICATION 49 + */ 50 + struct watch_notification_removal { 51 + struct watch_notification watch; 52 + __u64 id; /* Type-dependent identifier */ 53 + }; 54 + 55 + #endif /* _UAPI_LINUX_WATCH_QUEUE_H */