Messages in this thread | | | Date | Fri, 26 Nov 1999 15:28:37 -0600 (CST) | From | Oliver Xymoron <> | Subject | Re: Request for comments (kdev_t and friends...) |
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On Fri, 26 Nov 1999, Richard Gooch wrote:
> Oliver Xymoron writes: > > In fact, we should add at least a void *private so that devices can > > be freed of managing their instance data with static arrays indexed > > off minor number. > > With devfs this is really clean. A driver can allocate an instance > structure at probe time, and pass the pointer to devfs_register(). > When the device node is opened, file->private_data is initialised with > that pointer. So the driver open() method already has a handle to the > device instance structure, without any lookups being required.
That part of the scheme is good, but I'm still not convinced the lookup is a big deal. To open a file, you still end up doing a lookup that matches name to device (ie a dentry hash lookup). There's no reason opening a device couldn't use a similarly fast (or even identical!) method without requiring that the /dev dir be managed inside the kernel. In fact, I think I earlier suggested it's possible to cache the lookup in the inode.
-- "Love the dolphins," she advised him. "Write by W.A.S.T.E.."
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