Subject: Re: PR 31468 -- distributed LKMs are not useful because of incompatible config
To: Chuck Silvers <>
From: Nathan J. Williams <>
List: tech-kern
Date: 10/30/2005 12:39:11
Chuck Silvers <> writes:

> does anyone object to turning off DIAGNOSTIC in all the GENERIC configs?
> this seems like reasonable anyway, and it fixes this issue in nicely.

Why is this preferable to turning *on* DIAGNOSTIC in all the GENERIC

>  - these structures have an extra field if DIAGNOSTIC is on:
> 	struct irframe_softc
> 	struct usbd_xfer
> 	struct wsemul_vt100_emuldata
> 	struct cpu_data

The one DIAGNOSTIC field in usbd_xfer is only accessed by the host
controller driver (including allocation and deallocation), so its
presence or absence just affects offsets. Would it be sufficent to
move it to the end of the structure? Alternately, keeping 4 extra
bytes on a 112-byte structure (on ILP32) isn't much to worry about.

For the rest it seems pretty clear that the structures aren't numerous
enough for size to be a big concern. It's probably worth marking that
those members aren't filled with valid data if DIAGNOSTIC is off.

        - Nathan