src/libudev/libudev-hwdb.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright Tom Gundersen <teg@jklm.no>
   6
   7   systemd is free software; you can redistribute it and/or modify it
   8   under the terms of the GNU Lesser General Public License as published by
   9   the Free Software Foundation; either version 2.1 of the License, or
  10   (at your option) any later version.
  11
  12   systemd is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   Lesser General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  19 ***/
  20
  21 #include "sd-hwdb.h"
  22
  23 #include "alloc-util.h"
  24 #include "hwdb-util.h"
  25 #include "libudev-private.h"
  26
  27 /**
  28  * SECTION:libudev-hwdb
  29  * @short_description: retrieve properties from the hardware database
  30  *
  31  * Libudev hardware database interface.
  32  */
  33
  34 /**
  35  * udev_hwdb:
  36  *
  37  * Opaque object representing the hardware database.
  38  */
  39 struct udev_hwdb {
  40         struct udev *udev;
  41         int refcount;
  42
  43         sd_hwdb *hwdb;
  44
  45         struct udev_list properties_list;
  46 };
  47
  48 /**
  49  * udev_hwdb_new:
  50  * @udev: udev library context
  51  *
  52  * Create a hardware database context to query properties for devices.
  53  *
  54  * Returns: a hwdb context.
  55  **/
  56 _public_ struct udev_hwdb *udev_hwdb_new(struct udev *udev) {
  57         _cleanup_(sd_hwdb_unrefp) sd_hwdb *hwdb_internal = NULL;
  58         struct udev_hwdb *hwdb;
  59         int r;
  60
  61         assert_return_errno(udev, NULL, EINVAL);
  62
  63         r = sd_hwdb_new(&hwdb_internal);
  64         if (r < 0) {
  65                 errno = -r;
  66                 return NULL;
  67         }
  68
  69         hwdb = new0(struct udev_hwdb, 1);
  70         if (!hwdb) {
  71                 errno = ENOMEM;
  72                 return NULL;
  73         }
  74
  75         hwdb->refcount = 1;
  76         hwdb->hwdb = hwdb_internal;
  77         hwdb_internal = NULL;
  78
  79         udev_list_init(udev, &hwdb->properties_list, true);
  80
  81         return hwdb;
  82 }
  83
  84 /**
  85  * udev_hwdb_ref:
  86  * @hwdb: context
  87  *
  88  * Take a reference of a hwdb context.
  89  *
  90  * Returns: the passed enumeration context
  91  **/
  92 _public_ struct udev_hwdb *udev_hwdb_ref(struct udev_hwdb *hwdb) {
  93         if (!hwdb)
  94                 return NULL;
  95         hwdb->refcount++;
  96         return hwdb;
  97 }
  98
  99 /**
 100  * udev_hwdb_unref:
 101  * @hwdb: context
 102  *
 103  * Drop a reference of a hwdb context. If the refcount reaches zero,
 104  * all resources of the hwdb context will be released.
 105  *
 106  * Returns: #NULL
 107  **/
 108 _public_ struct udev_hwdb *udev_hwdb_unref(struct udev_hwdb *hwdb) {
 109         if (!hwdb)
 110                 return NULL;
 111         hwdb->refcount--;
 112         if (hwdb->refcount > 0)
 113                 return NULL;
 114         sd_hwdb_unref(hwdb->hwdb);
 115         udev_list_cleanup(&hwdb->properties_list);
 116         free(hwdb);
 117         return NULL;
 118 }
 119
 120 /**
 121  * udev_hwdb_get_properties_list_entry:
 122  * @hwdb: context
 123  * @modalias: modalias string
 124  * @flags: (unused)
 125  *
 126  * Lookup a matching device in the hardware database. The lookup key is a
 127  * modalias string, whose formats are defined for the Linux kernel modules.
 128  * Examples are: pci:v00008086d00001C2D*, usb:v04F2pB221*. The first entry
 129  * of a list of retrieved properties is returned.
 130  *
 131  * Returns: a udev_list_entry.
 132  */
 133 _public_ struct udev_list_entry *udev_hwdb_get_properties_list_entry(struct udev_hwdb *hwdb, const char *modalias, unsigned int flags) {
 134         const char *key, *value;
 135         struct udev_list_entry *e;
 136
 137         if (!hwdb || !modalias) {
 138                 errno = EINVAL;
 139                 return NULL;
 140         }
 141
 142         udev_list_cleanup(&hwdb->properties_list);
 143
 144         SD_HWDB_FOREACH_PROPERTY(hwdb->hwdb, modalias, key, value) {
 145                 if (udev_list_entry_add(&hwdb->properties_list, key, value) == NULL) {
 146                         errno = ENOMEM;
 147                         return NULL;
 148                 }
 149         }
 150
 151         e = udev_list_get_entry(&hwdb->properties_list);
 152         if (!e)
 153                 errno = ENODATA;
 154
 155         return e;
 156 }