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devtmpfs to lose EXPERIMENTAL tag

By Jake Edge
January 20, 2010
In a fairly short period of time, devtmpfs has gone from a controversial proposal in May to being merged into the mainline for 2.6.32. It was merged as an experimental feature, though, which is something the devtmpfs developers would like to see change. Kay Sievers posted a patch that would remove the experimental designation as well as make it the default: "All major distros enable devtmpfs on recent systems, so remove the EXPERIMENTAL flag, and enable it by default to reflect how it is used today."

Comments on the patch indicate that there is little complaint about removing the experimental designation, but making it the default was not particularly popular. Arjan van de Ven complained that enabling devtmpfs by default violated a kernel convention: "we use 'default y' only for those things that used to be on, and are now turned into a config option." Sievers, at least, had never heard of that convention, but is willing to follow it—if it exists.

Alan Cox pointed out that existing distributions do not use devtmpfs, only those in development, but Sievers sees no harm for older systems:

And it should not harm any old system if it is enabled. If initramfs is used it's completely invisible, if a custom kernel with kernel-mounted rootfs is used, the udev boot script usually over-mounts the devtmpfs at /dev with an empty tmpfs, like it has always done it before.

It is unclear whether this change is meant for 2.6.33 or is just being floated early for the 2.6.34 merge window, but the removal of EXPERIMENTAL seems to have no real opposition. Whether it becomes the default or not looks to be up in the air, but in a fairly short period of time, devtmpfs has cemented its place in the mainline kernel.


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