As well as updating some internal docs so they're current, this patch adds the physical path to the data available through hotplugging. This feature was requested at the LinuxKongress hotplug BOF, and was also on my 2.5 list.And is already present with the DEVPATH environment variable, right?No, DEVPATH isn't as stable as the physical path. And will not be available on 2.4 ... which will be important for a few years yet, particularly for layers above the kernel.Ok, but this was a patch for 2.5, right? We have DEVPATH, and don't need to have USB_PATH for 2.5.
They don't solve the same problems though, so we _do_ need something to solve the problem that usb_make_path() solves.
Plus, you were at pains to explain to me how DEVPATH should not be perceived as a physical path. They don't even try to address the same problems.Sure, but what is the problem? It's as stable as what you are trying to use, right?
No, as I had described. USB bus numbers are not stable, so having them in identifers is counter-productive: they reduce identifer stability.
Here's part of what I got from hotplugging one keyboard: DEVICE=/proc/bus/usb/001/006 ACTION=add TYPE=9/0/0 USB_PATH=usb-02:00.0-1.4 DEVPATH=root/pci0/00:03.0/02:00.0/usb1/1-1/1-1.4/1-1.4:0 PRODUCT=58f/9213/101 At best, DEVPATH needs a _lot_ of mangling to turn into the physical ID. And using long IDs is always error prone.But the last file in DEVPATH is equal to what you wanted to use in USB_PATH, right? And if you really wanted the pci id, it's there too.
You mean "1-1.4:0"? Compare -- only the "1.4" is significant. And it's not necessarily a PCI ID ... remember that USB is usable without PCI. That's an example of where any approach of trying to mangle DEVPATH is guaranteed to lose.
At worst, remember that identifiers like "pci0" and "usb1" change a lot more readily than "02:00.0". (Even on cardbus and similar hotplug pci, since most people have control over which slots they use.) Using DEVPATH would ensure that many more "should-be-minor" changes in system config will need sysadmin and tool attention. That's generally not-good, particularly when needs for routine tool use are so easy to avoid ... save tool work for the important stuff!But I don't want to drag around two naming schemes for devices, let's stick to the one the rest of the kernel is going to use, DEVPATH.
The rest of the kernel has quite a few schemes for identifying devices, each appropriate to the problem at hand. DEVPATH isn't really helpful in all cases; it isn't used everywhere (can't be).
Simpler for you to just edit out the USB_PATH fragment of the patch.I do like your comment cleanups, if you want to send me that part of the patch again.
- Dave
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