The path-id plugin does not work for mmc cards anymore: # new-udevadm test-builtin path_id /sys/block/mmcblk0 calling: test-builtin load module index unload module index # new-udevadm --version 186 (from cd96b3b86abb4a88cac2722bdfb6e5d4413f6831 git) An old version returns: # udevadm test-builtin path_id /sys/block/mmcblk0 run_command: calling: test-builtin builtin_kmod_init: load module index udev_device_new_from_syspath: device 0x5663f0 has devpath '/devices/platform/mxs-mmc.0/mmc_host/mmc0/mmc0:b368/block/mmcblk0' udev_device_new_from_syspath: device 0x5673c8 has devpath '/devices/platform/mxs-mmc.0/mmc_host/mmc0/mmc0:b368' udev_device_new_from_syspath: device 0x567730 has devpath '/devices/platform/mxs-mmc.0/mmc_host/mmc0' udev_device_new_from_syspath: device 0x567a88 has devpath '/devices/platform/mxs-mmc.0' udev_device_new_from_syspath: device 0x567dc0 has devpath '/devices/platform' udev_builtin_add_property: ID_PATH=platform-mxs-mmc.0 ID_PATH=platform-mxs-mmc.0 udev_builtin_add_property: ID_PATH_TAG=platform-mxs-mmc_0 ID_PATH_TAG=platform-mxs-mmc_0 builtin_kmod_exit: unload module index # new-udevadm --version 182
We suppress all the "useless" links now. The path to a platform device is pretty pointless, it just repeats the kernel device name and usually does not provide any add-on value. The by-path links are mainly for complex storage topologies, and identify more positions on a bus than a device. They probably have no real meaning for things like mmc. What would you need it for? Why would by-path/ here any better than the kernel device name?
The kernel device name does not identify the physical device but depends on random events. E.g. I have a platform with two sdhci controllers with different purposes. First slot is an external slot while second one is internal with a non-removable card. When there is a card in the external slot at boot, the non-removable card is named 'mmcblk1'; without the external card it is 'mmcblk0'. Vice versa for the external card. Mounting the correct card requires knowledge about physical position which worked fine previously with the /dev/disk/by-path symlink.
Ok, convinced, sounds useful. This should fix it: http://cgit.freedesktop.org/systemd/systemd/commit/?id=2a3fe9a75951cb085b81569939f6af3ce2eb2b02
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