From: Jean DELVARE <jdelvare@suse.com>
To: Greg KH <gregkh@linuxfoundation.org>,
Paul Menzel <pmenzel@molgen.mpg.de>
Cc: stable@vger.kernel.org, Wolfram Sang <wsa@kernel.org>,
linux-i2c@vger.kernel.org
Subject: Re: Please backport commit 13e3a512a290 (i2c: smbus: Support up to 8 SPD EEPROMs)
Date: Thu, 28 Mar 2024 15:51:35 +0100 [thread overview]
Message-ID: <cf21b9dd6499d3e6fa8d9e8c46d77eb035e9c7b5.camel@suse.com> (raw)
In-Reply-To: <2024032814-colony-observant-4e42@gregkh>
Hi Greg, Paul,
On Thu, 2024-03-28 at 07:10 +0100, Greg KH wrote:
> On Wed, Mar 27, 2024 at 09:35:38PM +0100, Paul Menzel wrote:
> > Am 27.03.24 um 17:52 schrieb Greg KH:
> > > On Wed, Mar 27, 2024 at 04:13:26PM +0100, Paul Menzel wrote:
> >
> > > > Please apply commit 13e3a512a290 (i2c: smbus: Support up to 8
> > > > SPD EEPROMs) [1] to the stable series to get rid of a warning
> > > > and to support more SPDs.
> > > > That commit is present since v6.8-rc1.
> > >
> > > How far back?
> >
> > I’d say 6.1.
> >
> > > But isn't this a new feature, why is it needed in older kernels?
> > > It's not a fix for a regression.
> > decode-dimm does not work on systems with more than four SPD
> > EEPROMs, so I’d say it’s a fix.
>
> But it's never worked on such systems so it's not a regression fix,
> right?
It's hard to qualify whether this is a regression or not.
On the one hand, automatic detection of SPD EEPROMs only ever supported
4 modules maximum (since kernel v5.8):
01590f361e94 ("i2c: i801: Instantiate SPD EEPROMs automatically")
5ace60859e84 ("i2c: smbus: Add a way to instantiate SPD EEPROMs automatically")
OTOH, this was implemented using the at24 driver, which replaced the
legacy eeprom driver. Said legacy driver was removed in kernel v6.7:
0113a99b8a75 ("eeprom: Remove deprecated legacy eeprom driver")
As it would be possible to see up to 8 SPD EEPROMs using the legacy
eeprom driver, and only 4 when using the at24 driver, you could say
that kernel v6.7 suffers from a regression. So backporting commit
13e3a512a290 to 6.7-stable would make sense.
> Anyway, I'll defer to the i2c maintainers as to what they want to
> have happen here, as they did not originally tag this commit for
> stable inclusion.
I'm definitely in favor of backporting 13e3a512a290 to 6.7-stable.
For older kernels, I'm not so sure, as there's a fairly easy
workaround: loading the legacy eeprom driver should let decode-dimms
see all memory modules (modules 1-4 using the at24 driver and modules
5-8 using the eeprom driver). Paul, can you try and confirm that this
does work?
--
Jean Delvare
SUSE L3 Support
prev parent reply other threads:[~2024-03-28 14:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3bea11ec-32fe-4288-bc03-8c3ba63979f6@molgen.mpg.de>
[not found] ` <2024032713-atom-saxophone-0c15@gregkh>
2024-03-27 20:35 ` Please backport commit 13e3a512a290 (i2c: smbus: Support up to 8 SPD EEPROMs) Paul Menzel
2024-03-28 6:10 ` Greg KH
2024-03-28 14:51 ` Jean DELVARE [this message]
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