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 = TAKE_PTR(hwdb_internal);
  77
  78         udev_list_init(udev, &hwdb->properties_list, true);
  79
  80         return hwdb;
  81 }
  82
  83 /**
  84  * udev_hwdb_ref:
  85  * @hwdb: context
  86  *
  87  * Take a reference of a hwdb context.
  88  *
  89  * Returns: the passed enumeration context
  90  **/
  91 _public_ struct udev_hwdb *udev_hwdb_ref(struct udev_hwdb *hwdb) {
  92         if (!hwdb)
  93                 return NULL;
  94         hwdb->refcount++;
  95         return hwdb;
  96 }
  97
  98 /**
  99  * udev_hwdb_unref:
 100  * @hwdb: context
 101  *
 102  * Drop a reference of a hwdb context. If the refcount reaches zero,
 103  * all resources of the hwdb context will be released.
 104  *
 105  * Returns: #NULL
 106  **/
 107 _public_ struct udev_hwdb *udev_hwdb_unref(struct udev_hwdb *hwdb) {
 108         if (!hwdb)
 109                 return NULL;
 110         hwdb->refcount--;
 111         if (hwdb->refcount > 0)
 112                 return NULL;
 113         sd_hwdb_unref(hwdb->hwdb);
 114         udev_list_cleanup(&hwdb->properties_list);
 115         return mfree(hwdb);
 116 }
 117
 118 /**
 119  * udev_hwdb_get_properties_list_entry:
 120  * @hwdb: context
 121  * @modalias: modalias string
 122  * @flags: (unused)
 123  *
 124  * Lookup a matching device in the hardware database. The lookup key is a
 125  * modalias string, whose formats are defined for the Linux kernel modules.
 126  * Examples are: pci:v00008086d00001C2D*, usb:v04F2pB221*. The first entry
 127  * of a list of retrieved properties is returned.
 128  *
 129  * Returns: a udev_list_entry.
 130  */
 131 _public_ struct udev_list_entry *udev_hwdb_get_properties_list_entry(struct udev_hwdb *hwdb, const char *modalias, unsigned int flags) {
 132         const char *key, *value;
 133         struct udev_list_entry *e;
 134
 135         if (!hwdb || !modalias) {
 136                 errno = EINVAL;
 137                 return NULL;
 138         }
 139
 140         udev_list_cleanup(&hwdb->properties_list);
 141
 142         SD_HWDB_FOREACH_PROPERTY(hwdb->hwdb, modalias, key, value) {
 143                 if (udev_list_entry_add(&hwdb->properties_list, key, value) == NULL) {
 144                         errno = ENOMEM;
 145                         return NULL;
 146                 }
 147         }
 148
 149         e = udev_list_get_entry(&hwdb->properties_list);
 150         if (!e)
 151                 errno = ENODATA;
 152
 153         return e;
 154 }