e77b146f82
This tries to address the "bind"/"unbind" uevent kernel API breakage, by changing the semantics of device tags. Previously, tags would be applied on uevents (and the database entries they result in) only depending on the immediate context. This means that if one uevent causes the tag to be set and the next to be unset, this would immediately effect what apps would see and the database entries would contain each time. This is problematic however, as tags are a filtering concept, and if tags vanish then clients won't hence notice when a device stops being relevant to them since not only the tags disappear but immediately also the uevents for it are filtered including the one necessary for the app to notice that the device lost its tag and hence relevance. With this change tags become "sticky". If a tag is applied is once applied to a device it will stay in place forever, until the device is removed. Tags can never be removed again. This means that an app watching a specific set of devices by filtering for a tag is guaranteed to not only see the events where the tag is set but also all follow-up events where the tags might be removed again. This change of behaviour is unfortunate, but is required due to the kernel introducing new "bind" and "unbind" uevents that generally have the effect that tags and properties disappear and apps hence don't notice when a device looses relevance to it. "bind"/"unbind" events were introduced in kernel 4.12, and are now used in more and more subsystems. The introduction broke userspace widely, and this commit is an attempt to provide a way for apps to deal with it. While tags are now "sticky" a new automatic device property CURRENT_TAGS is introduced (matching the existing TAGS property) that always reflects the precise set of tags applied on the most recent events. Thus, when subscribing to devices through tags, all devices that ever had the tag put on them will be be seen, and by CURRENT_TAGS it may be checked whether the device right at the moment matches the tag requirements. See: #7587 #7018 #8221
128 lines
6 KiB
C
128 lines
6 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#ifndef foosddevicehfoo
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#define foosddevicehfoo
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/***
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <inttypes.h>
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#include <sys/sysmacros.h>
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#include <sys/types.h>
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#include "sd-event.h"
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#include "_sd-common.h"
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_SD_BEGIN_DECLARATIONS;
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typedef struct sd_device sd_device;
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typedef struct sd_device_enumerator sd_device_enumerator;
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typedef struct sd_device_monitor sd_device_monitor;
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/* callback */
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typedef int (*sd_device_monitor_handler_t)(sd_device_monitor *m, sd_device *device, void *userdata);
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/* device */
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sd_device *sd_device_ref(sd_device *device);
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sd_device *sd_device_unref(sd_device *device);
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int sd_device_new_from_syspath(sd_device **ret, const char *syspath);
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int sd_device_new_from_devnum(sd_device **ret, char type, dev_t devnum);
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int sd_device_new_from_subsystem_sysname(sd_device **ret, const char *subsystem, const char *sysname);
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int sd_device_new_from_device_id(sd_device **ret, const char *id);
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int sd_device_get_parent(sd_device *child, sd_device **ret);
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int sd_device_get_parent_with_subsystem_devtype(sd_device *child, const char *subsystem, const char *devtype, sd_device **ret);
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int sd_device_get_syspath(sd_device *device, const char **ret);
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int sd_device_get_subsystem(sd_device *device, const char **ret);
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int sd_device_get_devtype(sd_device *device, const char **ret);
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int sd_device_get_devnum(sd_device *device, dev_t *devnum);
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int sd_device_get_ifindex(sd_device *device, int *ifindex);
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int sd_device_get_driver(sd_device *device, const char **ret);
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int sd_device_get_devpath(sd_device *device, const char **ret);
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int sd_device_get_devname(sd_device *device, const char **ret);
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int sd_device_get_sysname(sd_device *device, const char **ret);
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int sd_device_get_sysnum(sd_device *device, const char **ret);
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int sd_device_get_is_initialized(sd_device *device);
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int sd_device_get_usec_since_initialized(sd_device *device, uint64_t *usec);
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const char *sd_device_get_tag_first(sd_device *device);
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const char *sd_device_get_tag_next(sd_device *device);
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const char *sd_device_get_current_tag_first(sd_device *device);
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const char *sd_device_get_current_tag_next(sd_device *device);
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const char *sd_device_get_devlink_first(sd_device *device);
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const char *sd_device_get_devlink_next(sd_device *device);
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const char *sd_device_get_property_first(sd_device *device, const char **value);
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const char *sd_device_get_property_next(sd_device *device, const char **value);
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const char *sd_device_get_sysattr_first(sd_device *device);
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const char *sd_device_get_sysattr_next(sd_device *device);
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int sd_device_has_tag(sd_device *device, const char *tag);
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int sd_device_has_current_tag(sd_device *device, const char *tag);
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int sd_device_get_property_value(sd_device *device, const char *key, const char **value);
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int sd_device_get_sysattr_value(sd_device *device, const char *sysattr, const char **_value);
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int sd_device_set_sysattr_value(sd_device *device, const char *sysattr, const char *value);
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/* device enumerator */
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int sd_device_enumerator_new(sd_device_enumerator **ret);
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sd_device_enumerator *sd_device_enumerator_ref(sd_device_enumerator *enumerator);
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sd_device_enumerator *sd_device_enumerator_unref(sd_device_enumerator *enumerator);
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sd_device *sd_device_enumerator_get_device_first(sd_device_enumerator *enumerator);
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sd_device *sd_device_enumerator_get_device_next(sd_device_enumerator *enumerator);
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sd_device *sd_device_enumerator_get_subsystem_first(sd_device_enumerator *enumerator);
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sd_device *sd_device_enumerator_get_subsystem_next(sd_device_enumerator *enumerator);
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int sd_device_enumerator_add_match_subsystem(sd_device_enumerator *enumerator, const char *subsystem, int match);
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int sd_device_enumerator_add_match_sysattr(sd_device_enumerator *enumerator, const char *sysattr, const char *value, int match);
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int sd_device_enumerator_add_match_property(sd_device_enumerator *enumerator, const char *property, const char *value);
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int sd_device_enumerator_add_match_sysname(sd_device_enumerator *enumerator, const char *sysname);
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int sd_device_enumerator_add_match_tag(sd_device_enumerator *enumerator, const char *tag);
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int sd_device_enumerator_add_match_parent(sd_device_enumerator *enumerator, sd_device *parent);
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int sd_device_enumerator_allow_uninitialized(sd_device_enumerator *enumerator);
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/* device monitor */
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int sd_device_monitor_new(sd_device_monitor **ret);
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sd_device_monitor *sd_device_monitor_ref(sd_device_monitor *m);
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sd_device_monitor *sd_device_monitor_unref(sd_device_monitor *m);
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int sd_device_monitor_set_receive_buffer_size(sd_device_monitor *m, size_t size);
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int sd_device_monitor_attach_event(sd_device_monitor *m, sd_event *event);
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int sd_device_monitor_detach_event(sd_device_monitor *m);
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sd_event *sd_device_monitor_get_event(sd_device_monitor *m);
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sd_event_source *sd_device_monitor_get_event_source(sd_device_monitor *m);
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int sd_device_monitor_start(sd_device_monitor *m, sd_device_monitor_handler_t callback, void *userdata);
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int sd_device_monitor_stop(sd_device_monitor *m);
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int sd_device_monitor_filter_add_match_subsystem_devtype(sd_device_monitor *m, const char *subsystem, const char *devtype);
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int sd_device_monitor_filter_add_match_tag(sd_device_monitor *m, const char *tag);
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int sd_device_monitor_filter_update(sd_device_monitor *m);
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int sd_device_monitor_filter_remove(sd_device_monitor *m);
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_SD_DEFINE_POINTER_CLEANUP_FUNC(sd_device, sd_device_unref);
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_SD_DEFINE_POINTER_CLEANUP_FUNC(sd_device_enumerator, sd_device_enumerator_unref);
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_SD_DEFINE_POINTER_CLEANUP_FUNC(sd_device_monitor, sd_device_monitor_unref);
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_SD_END_DECLARATIONS;
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#endif
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