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remove broken %e enumeration
This commit is contained in:
Kay Sievers
parent
f1e9ccb94d
commit
c8ff4b3db4
32
FAQ
32
FAQ
@ -14,7 +14,7 @@ A: udev works entirely in userspace, using hotplug events the kernel sends
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All device naming policy permission control and event handling is done in
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userspace. devfs is operated from within the kernel.
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Q: Why was devfs marked OBSOLETE/removed if udev can't do everthing devfs did?
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Q: Why was devfs removed if udev can't do everthing devfs did?
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A: To quote Al Viro (Linux VFS kernel maintainer):
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- it was determined that the same thing could be done in userspace
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- devfs had been shoved into the tree in hope that its quality will
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@ -46,31 +46,25 @@ A: The devfs approach caused a lot of spurious modprobe attempts as
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spurious.
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Q: I really like the devfs naming scheme, will udev do that?
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A: Yes, udev can create /dev nodes using the devfs naming policy. A
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configuration file needs to be created to map the kernel default names
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to the devfs names. See the udev.rules.devfs file in the udev
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release.
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Note that the devfs scheme is not recommended or officially supported
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because it is a really stupid idea to simply enumerate devices in a world
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where devices can come and go at any time. These numbers give you nothing
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but problems, and are not useful to identify a device. Have a look at the
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persistent disk rules for an example how to do it correctly in userspace
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without any stupid device enumeration.
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A: Yes, udev can create /dev nodes using the devfs naming policy. But you
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will need a custom configuration and scripts that enumerate your devices
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sequentially while events run in parallel, without a predictable order.
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The devfs scheme is not recommended or supported because it is a stupid
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idea to simply enumerate devices in a world where devices can come and go
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at any time. These numbers give you nothing but problems, and are not
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useful to identify a device. Have a look at the persistent rules for
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examples how to create persistent device names in userspace without any
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device enumeration depending on the device probing order.
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Q: What kinds of devices does udev create nodes for?
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A: All devices that are shown in sysfs will work with udev. If more
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support is added for devices to the kernel, udev will automatically
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start working for them. All block devices are currently supported, and
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almost all major char devices are supported. Kernel developers are
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working on adding support for all char devices at this time. See the
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linux-kernel mailing list for patches and status of these patches.
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A: All devices that are shown in the kernel's sysfs tree will work with udev.
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Q: Will udev remove the limit on the number of anonymous devices?
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A: udev is entirely in userspace. If the kernel supports a greater number
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of anonymous devices, udev will support it.
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Q: Will udev support symlinks?
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A: Yes, It now does. Multiple symlinks per device node are supported.
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Q: Does udev support symlinks?
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A: Yes, multiple symlinks per device node are supported.
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Q: How will udev handle the /dev filesystem?
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A: /dev is recomended to be a tmpfs filesystem that is recreated on every reboot.
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3
TODO
3
TODO
@ -7,9 +7,6 @@ These things need to be done, or would be nice to have:
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These things are deprecated and scheduled for removal in a future
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udev version:
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o remove broken %e enumeration
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(simple enumerations can't work reliably and should go)
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o remove udevstart
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(we rely on the kernel "uevent" triggers of kernel 2.6.15 and no longer
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want to guess event properties from sysfs like udevstart is doing it)
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@ -101,7 +101,7 @@ And now for udev:
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want to deviate away from this standard (for example when naming
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some devices in a persistent manner), it is easily possible to do
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so.
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3) udev is small (49Kb binary) and is entirely in userspace, which
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3) udev is small and is entirely in userspace, which
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is swapable, and doesn't have to be running at all times.
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Nice, 7 out of 7 for udev. Makes you think the problems and constraints
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@ -1008,74 +1008,6 @@ EOF
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exp_target => "node",
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rules => <<EOF
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BUS=="scsi", PROGRAM=="/bin/echo -n node link1 link2 link3 link4", RESULT=="node *", NAME="%c{1}", SYMLINK+="%c{2+}"
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EOF
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},
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{
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desc => "enumeration char test (single test)",
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subsys => "block",
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devpath => "/block/sda",
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exp_name => "cdrom",
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rules => <<EOF
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KERNEL=="sda", NAME="cdrom%e"
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EOF
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},
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{
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desc => "enumeration char test sequence 1/5 (keep)",
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subsys => "block",
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devpath => "/block/sda",
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exp_name => "cdrom",
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option => "keep",
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rules => <<EOF
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KERNEL=="sda", NAME="cdrom%e"
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EOF
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},
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{
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desc => "enumeration char test sequence 2/5 (keep)",
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subsys => "block",
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devpath => "/block/sda/sda1",
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exp_name => "enum",
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option => "keep",
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rules => <<EOF
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KERNEL=="sda1", NAME="enum%e"
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EOF
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},
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{
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desc => "enumeration char test sequence 3/5 (keep)",
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subsys => "block",
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devpath => "/block/sda/sda2",
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exp_name => "cdrom1",
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option => "keep",
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rules => <<EOF
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KERNEL=="sda2", NAME="cdrom%e"
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EOF
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},
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{
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desc => "enumeration char test sequence 4/5 (keep)",
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subsys => "block",
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devpath => "/block/sda/sda3",
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exp_name => "enum1",
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option => "keep",
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rules => <<EOF
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KERNEL=="sda3", NAME="enum%e"
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EOF
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},
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{
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desc => "enumeration char test sequence 5/5 (clean)",
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subsys => "block",
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devpath => "/block/sda/sda4",
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exp_name => "cdrom2",
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option => "clean",
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rules => <<EOF
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KERNEL=="sda4", NAME="cdrom%e"
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EOF
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},
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{
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desc => "enumeration char test after cleanup (single test)",
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subsys => "block",
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devpath => "/block/sda",
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exp_name => "cdrom",
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rules => <<EOF
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KERNEL=="sda", NAME="cdrom%e"
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EOF
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},
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{
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92
udev_rules.c
92
udev_rules.c
@ -263,88 +263,6 @@ static int import_parent_into_env(struct udevice *udev, const char *filter)
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return rc;
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}
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static int match_name_and_get_number(const char *base, const char *devname)
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{
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size_t baselen;
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char *endptr;
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int num;
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baselen = strlen(base);
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if (strncmp(base, devname, baselen) != 0)
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return -1;
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if (devname[baselen] == '\0')
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return 0;
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if (!isdigit(devname[baselen]))
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return -1;
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num = strtoul(&devname[baselen], &endptr, 10);
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if (endptr[0] != '\0')
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return -1;
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return num;
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}
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/* finds the lowest positive device number such that <name>N isn't present in the udevdb
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* if <name> doesn't exist, 0 is returned, N otherwise */
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static int find_free_number(const char *base, const char *devpath)
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{
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char db_devpath[PATH_SIZE];
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char filename[PATH_SIZE];
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struct udevice *udev_db;
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int num = 0;
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static int warn = 1;
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if (warn) {
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err("%%e is deprecated, will be removed and is unlikely to work correctly. Don't use it.");
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warn = 0;
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}
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/* check if the device already owns a matching name */
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udev_db = udev_device_init();
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if (udev_db == NULL)
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return -1;
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if (udev_db_get_device(udev_db, devpath) == 0) {
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struct name_entry *name_loop;
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int devnum;
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devnum = match_name_and_get_number(base, udev_db->name);
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if (devnum >= 0) {
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num = devnum;
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dbg("device '%s', already has the node '%s' with num %u, use it", devpath, base, num);
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goto out;
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}
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list_for_each_entry(name_loop, &udev_db->symlink_list, node) {
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devnum = match_name_and_get_number(base, name_loop->name);
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if (devnum >= 0) {
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num = devnum;
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dbg("device '%s', already has a symlink '%s' with num %u, use it", devpath, base, num);
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goto out;
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}
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}
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}
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/* just search the database again and again until a free name is found */
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strlcpy(filename, base, sizeof(filename));
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while (1) {
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dbg("look for existing node '%s'", filename);
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if (udev_db_lookup_name(filename, db_devpath, sizeof(db_devpath)) != 0) {
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dbg("free num=%d", num);
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break;
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}
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num++;
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if (num > 100000) {
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err("find_free_number aborted at num=%d", num);
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num = -1;
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break;
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}
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snprintf(filename, sizeof(filename), "%s%d", base, num);
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filename[sizeof(filename)-1] = '\0';
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}
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out:
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udev_device_cleanup(udev_db);
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return num;
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}
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#define WAIT_LOOP_PER_SECOND 50
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static int wait_for_sysfs(struct udevice *udev, const char *file, int timeout)
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{
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@ -386,7 +304,6 @@ void udev_rules_apply_format(struct udevice *udev, char *string, size_t maxsize)
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int len;
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int i;
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int count;
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unsigned int next_free_number;
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enum subst_type {
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SUBST_UNKNOWN,
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SUBST_DEVPATH,
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@ -397,7 +314,6 @@ void udev_rules_apply_format(struct udevice *udev, char *string, size_t maxsize)
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SUBST_MINOR,
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SUBST_RESULT,
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SUBST_SYSFS,
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SUBST_ENUM,
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SUBST_PARENT,
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SUBST_TEMP_NODE,
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SUBST_ROOT,
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@ -416,7 +332,6 @@ void udev_rules_apply_format(struct udevice *udev, char *string, size_t maxsize)
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{ .name = "minor", .fmt = 'm', .type = SUBST_MINOR },
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{ .name = "result", .fmt = 'c', .type = SUBST_RESULT },
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{ .name = "sysfs", .fmt = 's', .type = SUBST_SYSFS },
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{ .name = "enum", .fmt = 'e', .type = SUBST_ENUM },
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{ .name = "parent", .fmt = 'P', .type = SUBST_PARENT },
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{ .name = "tempnode", .fmt = 'N', .type = SUBST_TEMP_NODE },
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{ .name = "root", .fmt = 'r', .type = SUBST_ROOT },
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@ -572,13 +487,6 @@ found:
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dbg("substitute sysfs value '%s'", temp2);
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}
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break;
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case SUBST_ENUM:
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next_free_number = find_free_number(string, udev->dev->devpath);
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if (next_free_number > 0) {
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sprintf(temp2, "%d", next_free_number);
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strlcat(string, temp2, maxsize);
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}
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break;
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case SUBST_PARENT:
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{
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struct sysfs_device *dev_parent;
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