Re: kern/55958: pciback.hide parsing error

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

The following reply was made to PR kern/55958; it has been noted by GNATS.

From: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
To: Aleksey Arens <aza.sea.agenda%gmail.com@localhost>
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost,
        gnats-bugs%netbsd.org@localhost
Subject: Re: kern/55958: pciback.hide parsing error
Date: Wed, 27 Jan 2021 08:45:55 +0100

 On Tue, Jan 26, 2021 at 06:36:26PM -0800, Aleksey Arens wrote:
 > I wonder if the following solution may be acceptable.  Since the
 > change implies a difference in ABI, would it be possible to schedule
 > it for a next major release (for instance, release 10)?  I also
 > wonder, if the change could go into -current at this point; as I
 > understand, -current is not expected to maintain strict binary
 > compatibility.
 > 
 > I suppose that the proper approach to adding this might involve adding
 > #ifdef-s that checks for COMPAT_XX options.  Though, I think that a
 > more proper implementation would be to check at runtime for the module
 > version, and decide upon what buffer length for parameter passing
 > could be used accordingly.  I could work this code out, in principle;
 > I would appreciate a suggestion on what would be the best, most
 > compatible with the tradition, way to handle the hard-coded constant
 > in the header file.
 
 We must be able to boot a new kernel with an older /boot (this is a requirement
 for upgrade anyway), so some compat mechanism at the boot structure 
 level is neeed.
 
 And actually it's easy: leave bi_modulelist alone, and define a
 btinfo_modulelist2, associated with a BTINFO_MODULELIST2
 Have the boot loader fill both, and the kernel check first BTINFO_MODULELIST2
 and then BTINFO_MODULELIST. This way you can boot an old kernel with
 newer /boot, or the opposite.
 While there, put path[] at the end of bi_modulelist_entry2, so it can
 be arbitrary long.
 
 -- 
 Manuel Bouyer <bouyer%antioche.eu.org@localhost>
      NetBSD: 26 ans d'experience feront toujours la difference
 --