Messages in this thread | | | Date | Tue, 10 Feb 2004 10:29:44 -0800 | From | Mike Bell <> | Subject | Re: devfs vs udev, thoughts from a devfs user |
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On Tue, Feb 10, 2004 at 10:12:42AM -0800, Greg KH wrote: > No, that is not true. devfs exports the device node itself. It does > not just export the major:minor number.
That's a pretty minor difference, from the kernel's point of view. It's basically putting the same numbers in different fields.
> devfs also does not export the position within the entire device tree, > which sysfs does.
devfs tried to do just that. sysfs does it better though. I don't see what that has to do with my point.
> They are two completely different filesystems, doing two completely > different things. Please do not confuse them.
sysfs and devfs are very different. I said they both accomplish one common goal, sysfs for udev and devfs for devfsd.
> But the main point is that udev is in userspace, and devfs is in the > kernel. You forgot that :)
No I didn't. udev is userspace, devfsd is userspace. devfs is kernel space, sysfs is kernel space. They're the same.
> sysfs has no such "naming policy". It merely exports the name that the > kernel happened to give the device, using the LSB naming scheme. It > does not rely on driver substems to create subdirectories for their > devices, nor export their own nested naming schemes.
But sysfs is still setting naming policy in the kernel. Because you didn't write the kernelspace static names in question, they don't exist?
> sysfs merely exports the info that the kernel knows about a device, by > which udev creates a device node.
devfs merely exports information the kernel knows, by which devfsd can create device nodes.
> devfs exports the device node, and then lets devfsd override that node > and create other stuff.
And sysfs exports files that are (from a kernel point of view) very nearly a device node.
> Please also do not overlook the fragility of the devfs->devfsd > interface. It is binary, relies on 1 sender and 1 receiver, and doesn't > allow any other programs to get this info.
Didn't say the current devfs was a good implementation of the concept. Said I liked a devfs-like concept.
> But the point is that udev does not require such a interface as devfs to > get the job done. devfsd does.
Yes it does, it requires sysfs.
> Providing specific examples of what you find lacking in udev would be > constructive. Saying, "I don't like it as it doesn't feel right to me" > is merely wanting to pick a fight.
udev tries to do the job without a devfs. I said that already. I think there should be a kernel exported filesystem with kernel-created device nodes, and that udev's role should continue to do something similar to what it does now (manage permissions and user-supplied names), only on that kernel-exported filesystem. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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