Static Device Nodes

This page is under construction

FIXTHIS - This boot-time reduction method needs to be verified. Does it actually save time to statically create the device nodes? Does it avoid probing or setup time at boot time?

See this lore thread for a discussion on different ways to populate the device nodes for a system on startup.

Description

Use static device nodes instead of a dynamic device discovery mechanism like udev, mdev or devtmpfs. In an embedded system it is often known what devices are present and in any case you know what drivers are available, so you know what device entries might be needed in /dev. These should be created statically, not dynamically.

How to implement or use

Start your system the regular way, using either udev, mdev of devtmpfs. Take note of the device nodes in /dev. Write a script to mknod them manually, and use this script when creating the root filesystem for your system.

If it's possible for your embedded Linux system to have devices hotplugged at runtime (for example, if your product has a USB bus that things can be plugged into), then run your chosen hotplug tool after finishing your critical boot phase.

Expected Improvement

Describe the expected improvement, and any factors that affect it (such as memory size, number of processors, CPU frequency, etc.

Resources

Projects

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Specifications

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Patches

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Case Studies

Case 1

Hardware	hardware description
Kernel Version	put kernel version here
Configuration	list relevant kernel config options here
Time without using technique	xxxxxxx usec
Time using the technique	xxxxxxx usec
Time savings	mmm milliseconds
Submitter	name and company of submitter