Hans, The inline source file at the end of this post is a small program I used to play with libudev to see if it would complement the media controller concept (as you suspected it would). Documentation on the libudev calls is here: http://www.kernel.org/pub/linux/utils/kernel/hotplug/libudev/ The test program I wrote takes a (type,major,minor) tuple and lists the device node and device symlinks as fetched by libudev. My test setup was a little strange since libudev is no longer maintained separately but is bundled in with udev. On my Fedora 9 system I have udev v124 (Fedora 9 stock) and libudev v143 (custom built from the udev 143 source). Here's some output: $ ./finddev -c -M 1 -m 3 Requested device: type 'c', major 1, minor 3 Device directory path: '/dev' Device node: '/dev/null' Device link: '/dev/XOR' $ ls -al /dev/ | grep '[ /]null' crw-rw-rw- 1 root root 1, 3 2009-07-04 08:34 null lrwxrwxrwx 1 root root 4 2009-07-04 08:34 X0R -> null lrwxrwxrwx 1 root root 4 2009-07-04 08:34 XOR -> null (Hmmm, not perfect for /dev/null) $ ./finddev -b -M 11 -m 0 Requested device: type 'b', major 11, minor 0 Device directory path: '/dev' Device node: '/dev/sr0' Device link: '/dev/scd0' Device link: '/dev/disk/by-path/pci-0000:00:14.1-scsi-1:0:0:0' Device link: '/dev/cdrom' Device link: '/dev/cdrw' $ ls -alR /dev/* | grep '[ /]sr0' lrwxrwxrwx 1 root root 3 2009-07-04 08:34 /dev/cdrom -> sr0 lrwxrwxrwx 1 root root 3 2009-07-04 08:34 /dev/cdrw -> sr0 lrwxrwxrwx 1 root root 3 2009-07-04 08:34 /dev/scd0 -> sr0 brw-rw----+ 1 root disk 11, 0 2009-07-04 08:34 /dev/sr0 lrwxrwxrwx 1 root root 9 2009-07-04 08:34 pci-0000:00:14.1-scsi-1:0:0:0 -> ../../sr0 (OK for the CDROM drive.) $ ./finddev -c -M 81 -m 9 Requested device: type 'c', major 81, minor 9 Device directory path: '/dev' Device node: '/dev/video0' Device link: '/dev/video' $ ls -alR /dev/* | grep '[ /]video0' lrwxrwxrwx 1 root root 6 2009-07-04 08:34 /dev/video -> video0 crw-rw----+ 1 root root 81, 9 2009-07-04 08:34 /dev/video0 (OK for video nodes) $ ./finddev -c -M 116 -m 6 Requested device: type 'c', major 116, minor 6 Device directory path: '/dev' Device node: '/dev/snd/pcmC0D0p' $ ls -alR /dev/* | grep '[ /]pcmC0D0p' crw-rw----+ 1 root root 116, 6 2009-07-04 13:43 pcmC0D0p (OK for ALSA PCM stream nodes). Do you have any other particular questions about libudev's capabilities? Regards, Andy /* * finddev.c - Find a device node given (type,major,minor) using libudev * Copyright (C) 2009 Andy Walls <awalls@xxxxxxxxx> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. * * Compilation: * gcc -o finddev finddev.c -Wall -ludev * * Example invocation (/dev/null on my system): * ./finddev -c -M 1 -m 3 */ #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <libudev.h> struct parsed_args { int major; int minor; char type; }; int parse_args(int argc, char *argv[], struct parsed_args *args) { int c, ret; ret = 0; args->major = args->minor = -1; args->type = 'c'; while ((c = getopt(argc, argv, "bcM:m:")) != -1) { switch (c) { case 'b': args->type = 'b'; break; case 'c': args->type = 'c'; break; case 'M': args->major = atoi(optarg); break; case 'm': args->minor = atoi(optarg); break; default: ret = -1; break; } } if (ret || args->major == -1 || args->minor == -1) { fprintf(stderr, "Usage: %s [-b|-c] -M major -m minor\n", argv[0]); ret = -1; } return ret; } int main(int argc, char *argv[]) { struct parsed_args args; dev_t devnum; struct udev *udev; struct udev_device *udev_device; const char *s; struct udev_list_entry *udev_list_entry; if (parse_args(argc,argv, &args)) exit(1); printf("Requested device: type '%c', major %d, minor %d\n", args.type, args.major, args.minor); devnum = makedev(args.major, args.minor); udev = udev_new(); if (udev == NULL) { fprintf(stderr, "udev_new() failed\n"); exit(2); } printf("Device directory path: '%s'\n", udev_get_dev_path(udev)); udev_device = udev_device_new_from_devnum(udev, args.type, devnum); if (udev_device == NULL) { fprintf(stderr, "udev_device_new_from_devnum() failed\n"); udev_unref(udev); exit(3); } s = udev_device_get_devnode(udev_device); if (s) { printf("Device node: '%s'\n", s); } else { fprintf(stderr, "udev_device_get_devnode() failed\n"); udev_device_unref(udev_device); udev_unref(udev); exit(4); } udev_list_entry_foreach(udev_list_entry, udev_device_get_devlinks_list_entry(udev_device)) { s = udev_list_entry_get_name(udev_list_entry); printf("Device link: '%s'\n", s); } udev_device_unref(udev_device); udev_unref(udev); exit(0); } -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
