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From: Tony Battersby <tonyb@cybernetics.com>
To: Jiri Slaby <jirislaby@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org,
	Jari Ruusu <jariruusu@protonmail.com>,
	David Laight <David.Laight@ACULAB.COM>,
	Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>
Subject: Re: Kernel version numbers after 4.9.255 and 4.4.255
Date: Fri, 5 Feb 2021 12:31:05 -0500	[thread overview]
Message-ID: <0b12bac9-1b4e-ec4a-8a45-5eb3f1dbbeca@cybernetics.com> (raw)
In-Reply-To: <a85b7749-38b2-8ce9-c15a-8acb9a54c5b5@kernel.org>

On 2/4/21 6:00 AM, Jiri Slaby wrote:
> Agreed. But currently, sublevel won't "wrap", it will "overflow" to 
> patchlevel. And that might be a problem. So we might need to update the 
> header generation using e.g. "sublevel & 0xff" (wrap around) or 
> "sublevel > 255 : 255 : sublevel" (be monotonic and get stuck at 255).
>
> In both LINUX_VERSION_CODE generation and KERNEL_VERSION proper.

My preference would be to be monotonic and get stuck at 255 to avoid
breaking out-of-tree modules.  If needed, add another macro that
increases the number of bits that can be used to check for sublevels >
255, while keeping the old macros for compatibility reasons.  Since
sublevels > 255 have never existed before, any such checks must be
newly-added, so they can be required to use the new macros.

I do not run the 4.4/4.9 kernels usually, but I do sometimes test a wide
range of kernels from 3.18 (gasp!) up to the latest when bisecting,
benchmarking, or debugging problems.  And I use a number of out-of-tree
modules that rely on the KERNEL_VERSION to make everything work.  Some
out-of-tree modules like an updated igb network driver might be needed
to make it possible to test the old kernel on particular hardware.

In the worst case, I can patch LINUX_VERSION_CODE and KERNEL_VERSION
locally to make out-of-tree modules work.  Or else just not test kernels
with sublevel > 255.

Tony Battersby
Cybernetics



  parent reply	other threads:[~2021-02-05 17:51 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-04  5:59 Jari Ruusu
2021-02-04  6:20 ` Greg Kroah-Hartman
2021-02-04  7:26   ` Jiri Slaby
2021-02-04  8:51     ` Greg Kroah-Hartman
2021-02-04 11:00       ` Jiri Slaby
2021-02-04 16:28         ` David Laight
2021-02-04 16:48           ` Greg Kroah-Hartman
2021-02-04 20:19           ` Christoph Biedl
2021-02-05  6:52             ` Greg KH
2021-02-05 17:31         ` Tony Battersby [this message]
2021-02-05 18:11           ` Mauro Carvalho Chehab
2021-02-06  7:20             ` Greg Kroah-Hartman
2021-02-06  9:24               ` Mauro Carvalho Chehab
2021-02-06  9:29                 ` Greg Kroah-Hartman
2021-02-06  9:48                   ` Mauro Carvalho Chehab
2021-02-06 10:18                     ` Hans Verkuil
2021-02-06 11:18                       ` Mauro Carvalho Chehab
2021-02-06  7:22           ` Greg Kroah-Hartman
2021-02-05  9:06       ` Pavel Machek
2021-02-05  9:33         ` Greg Kroah-Hartman
2021-02-05 18:44           ` Pavel Machek
2021-02-06  7:23             ` Greg Kroah-Hartman

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