out of tree [LWN.net]

out of tree

Posted Aug 1, 2009 10:04 UTC (Sat) by nix (subscriber, #2304)
In reply to: out of tree by mikov
Parent article: A tempest in a tty pot

Let's say I am a manufacturer and I receive a bug report from a customer. How am I supposed to fix it? Submit a patch to LKML and tell the customer to wait for a new kernel version? That is absurd. So, I have to maintain an out-of-tree driver in any case. I want my customers to use the same driver in all kernel versions.

What? You maintain a git repo, the same way anyone else doing kernel development does, and feed one branch to Linus and the other to your customers. This is really not even slightly rocket science, and git has plenty of tools to help keep the branches in sync.

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out of tree

Posted Aug 1, 2009 16:29 UTC (Sat) by mikov (subscriber, #33179) [Link]

Oh, come on, the issue here is not the source control tool. Git is not magically going port your driver between versions. (BTW, I am a git fanatic, but that's another subject).

A successful compilation is not sufficient. Every release has to be exhaustively tested. Maintaining several slightly different versions of the same driver, plus tracking the yet different version which may or may not have been accepted in the mainline, is a lot of work. Especially if you have direct customers.

You absolutely need to maintain an out-of-tree driver. There is no two ways about it.

Look, this is not theoretical. This is my real experience and it has been that out of tree drivers are much more convenient for the users. If I need support for a piece of hardware, I download the module source, compile it and use it. No kernel upgrades, no backports, no crap. If I am going to install an out-of-tree driver, I actually prefer the mainline not to have one.

So, anything that makes it easier to maintain out of tree drivers would be good in my book. Of course everything must be GPL, and it would be nice if there was a centralized repository for these drivers so you don't have to hunt for them.

out of tree

Posted Aug 2, 2009 1:39 UTC (Sun) by foom (subscriber, #14868) [Link]

This is my real experience and it has been that out of tree drivers are much more convenient for the users.

As a user: yuck. Not only are out of tree drivers more irritating to use/install/upgrade than in-tree ones, my experience has been that they're also always buggier.

And I don't want to have to download the module source, compile it, and use it: I want the device to just work when I plug it in, without even thinking about it.

On the other hand, I do like it, when the driver is brand new, if an out-of-tree version is made available for use with older kernel versions. Certainly it's helpful to provide an out-of-tree version for the first year or two until everyone's upgraded to a kernel with the driver included already.

out of tree

Posted Aug 2, 2009 14:03 UTC (Sun) by alex (subscriber, #1355) [Link]

It would be nice if the distros could compile out-of-tree snapshots in a nice user friendly way. But for this to work they have to be GPL source code and not arbitrary binary blobs.

Certainly for me as a developer the current wireless testing tree/compat layer is an example of doing it right. I can run wireless with my distro kernel but still have the latest greatest without upgrading the kernel if I want. I wonder if more out-of-tree's could follow the wireless model.