netdev - Re: [patch] e1000=y && e1000e=m regression fix

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Date:	Fri, 11 Apr 2008 21:25:19 +0200
From:	Willy Tarreau <w@....eu>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	Ingo Molnar <mingo@...e.hu>, Jeff Garzik <jeff@...zik.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	NetDev <netdev@...r.kernel.org>,
	e1000-list <e1000-devel@...ts.sourceforge.net>,
	linux-pci maillist <linux-pci@...ey.karlin.mff.cuni.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	"Ronciak, John" <john.ronciak@...el.com>,
	"Allan, Bruce W" <bruce.w.allan@...el.com>,
	Greg KH <greg@...ah.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [patch] e1000=y && e1000e=m regression fix

On Fri, Apr 11, 2008 at 01:01:28PM -0600, Matthew Wilcox wrote:
> On Fri, Apr 11, 2008 at 11:51:07AM -0700, Linus Torvalds wrote:
> > Because your version has exactly the same problem that the current code 
> > has: it asks questions that aren't sensible to people who don't care. It 
> > also keeps the old E1000 name for "PCI chips only", which means that 
> > people who just use an old config and ignore new questions will suddenly 
> > lose their ability to use the E1000 driver if they have a PCI-E card.
> 
> We only support people keeping their old configs after they run 'make
> oldconfig', right?  At which point they'd be prompted for E1000_SUPPORT.
> Presumably they'd think "That's odd.  I'm sure I had that selected
> before", then select it.  Then oldconfig skips over CONFIG_E1000 because
> it already knows the answer to that one and they're prompted with a
> question about PCIe support.  Now something is clearly strange.  Perhaps
> they look at the help text at this point and it says to go with 'Y' or
> 'M' if they're not sure.

I don't think this will happen like that. People will simply think as
usual "ah, they have added support for new hardware, but since everything
in my machine was supported, I don't need it".

I think that the correct solution to help people is not at build time,
but at run time. The e1000 driver should just *check* if there are PCI-IDs
that it used to manage and that it does not anymore, for unclaimed devices,
and report a warning message clearly indicating that these devices are not
handled anymore and that for this, the user must load e1000e. It will :

  a) help people know what to load if they need to update modprobe.conf
  b) just require a new "make menuconfig;make modules" after the poor guy
     has been caught.

It's not a problem to have to tweak the config and reboot several times,
provided that the user is guided. Almost none of us has ever blindly
upgraded without a few post-boot adjustments.

> That's the most important bit of help texts for me.  Do I want Control
> Groups?  Will my machine break if I don't select them?  I have no idea
> what a 'process cgroup subsystem' is, and I don't care.  But the help
> text tells me I can say "n" and nothing will break.

Here if people don't know, they will reply "no" too.

> > So most users:
> >  - want to just say "E1000", and not care about type.
> >  - want to have old configurations continue working (ie if you haev had 
> >    "E1000" driving your hardware before, it should _continue_ to do so, 
> >    with no need to select a _new_ E1000E question!
> > 
> > Nobody wants to care deeply whether it's a PCI-E or PCI chip. In fact, 
> > it's almost impossible to tell. Here, quickly, tell me which one mine is 
> > (this is from /sbin/lspci):
> > 
> > 	00:19.0 Ethernet controller: Intel Corporation 82566DM Gigabit Network Connection (rev 02)
> 
> I quite agree.  I have no idea either.  All I know is that my ICH9 box
> didn't work until e1000e was released ;-)

I'm pretty sure it's PCI-E, because Linus got caught first ;-) But of
course, that should not be an accepted guess method.

Willy

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