[Buildroot] editing device_table_dev.txt
stefan.froberg at petroprogram.com
Thu Feb 21 10:14:35 UTC 2013
21.2.2013 1:37, John Stile kirjoitti:
> I need a better way to auto-populate /dev, using buildroot-2011.11, with
> 2.6.30 kernel, but it seems not matter what I do, /dev/ is not populated
> My config looks like this:
> # BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_DEVTMPFS is not set
> # BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV is not set
> # BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_UDEV is not set
> BR2_ROOTFS_DEVICE_TABLE="target/generic/device_table.txt target/generic/device_table_dev.txt"
> # BR2_ROOTFS_SKELETON_DEFAULT is not set
> To use hwclock I had to create dev/rtc0.
> Although my kernel argument contains mtdparts, the mtd* and mtdblock*
> devices are not created.
> There are others too.
> What should my config look like in order to auto-populate /dev?
Well, if you don't want to manually create your device nodes then there
are several ways to autopopulate /dev
Maybe the simplest would be just let the kernel handle it by mounting
/dev with tmpfs
So selecting BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_DEVTMPFS=y is the
Also kernel .config file should also have CONFIG_DEVTMPFS and DEVTMPFS
If you are using initramfs as your root system then kernel .config is
not enough but the /dev must be mounted manually
in /etc/fstab or somehwere in init-script (I think buildroot already
mount -t devtmpfs devtmpfs /dev
Next easiest is mdev. It needs /etc/mdev.conf file and somewhere in your
init script your should have
echo /sbin/mdev > /proc/sys/kernel/hotplug
BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV=y should be selected in that case.
Most complete but also maybe most complex in configuration is udev
Unlike previous two methods, devtmpfs and mdev, udev daemon (udevd) is
usually running continually and polling any events from
kernel when devices are plugged/unplugged.
Ofcourse if all you need is just the initial auto-creation of devices at
the boot time,
then devtmpfs or mdev would be perfectly enough.
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