Subject: Re: USB feedback wanted
To: None <firstname.lastname@example.org>
From: Lennart Augustsson <email@example.com>
Date: 06/30/1998 18:51:48
> There are an awful lot of files that live under sys/dev (that get
> installed into <dev/...>) that have ioctls, interfaces, etc., for
OK, I can move the files to dev/usb.
> You never mentioned what locators the various devices use. It's
> important to have those well-defined, and to have your config scheme
> structured such that somebody can uniquely identify and hard-code the
> identities of devices on their busses.
I don't use any locators. I'm not sure how thay can be used for USB.
Each USB device is can be queried for a descriptor which contains
a lot of information like vendor and product id, device class/subclass,
revision etc. I guess these could be locators, but I don't
see the point. It seems to work well without any locators.
Do you have an example of how it should be used in a USB setting?
> (Given the nature of hubs,
> some part of me wonders if the bus is best represented as 'hubs' and
> 'things which attach to hubs', i.e. have root hub as the root of the
> tree, devices and other hubs attached to it, etc.)
No. I thought about this, but I don't think this is a good idea.
Even if the physical structure is a tree, the logical structure is not
(USB devices are addressed on the bus with a (dynamically assigned)
number 1-127) and I don't think attaching devices to hubs would
improve anything. I'd also like to support unplugging a device and
the plugging it in again and have it continue working (this is not
possible now). In this case the device could move in the physical
tree, but it should still look the same for the attachment.