linux-kernel - Re: [PATCH] CCISS: Don't print driver version until we actually find a device

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Date:	Thu, 27 Jul 2006 09:56:50 -0400
From:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
To:	"gmu 2k6" <gmu2006@...il.com>
Cc:	"Jeff Garzik" <jeff@...zik.org>,
	"Arjan van de Ven" <arjan@...radead.org>,
	"Jesper Juhl" <jesper.juhl@...il.com>,
	"Bjorn Helgaas" <bjorn.helgaas@...com>,
	"Andrew Morton" <akpm@...l.org>,
	"Mike Miller" <mike.miller@...com>, iss_storagedev@...com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] CCISS: Don't print driver version until we actually find a device

On 7/27/06, gmu 2k6 <gmu2006@...il.com> wrote:
> On 7/27/06, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > On 7/26/06, Jeff Garzik <jeff@...zik.org> wrote:
> > > Arjan van de Ven wrote:
> > > > On Wed, 2006-07-26 at 00:43 +0200, Jesper Juhl wrote:
> > > >> On 26/07/06, Bjorn Helgaas <bjorn.helgaas@...com> wrote:
> > > >>> If we don't find any devices, we shouldn't print anything.
> > > >>>
> > > >> I disagree.
> > > >> I find it quite nice to be able to see that the driver loaded even if
> > > >> it finds nothing. At least then when there's a problem, I can quickly
> > > >> see that at least it is not because I didn't forget to load the
> > > >> driver, it's something else. Saves time since I can start looking for
> > > >> reasons why the driver didn't find anything without first spending
> > > >> additional time checking if I failed to cause it to load for some
> > > >> reason.
> > > >
> > > > I'll add a second reason: it is a REALLY nice property to be able to see
> > > > which driver is started last in case of a crash/hang, so that the guilty
> > > > party is more obvious..
> > >
> > > OTOH, it is not a property that scales well at all.
> > >
> > > When you build extra drivers into the kernel, or distros load drivers
> > > you don't need (_every_ distro does this), you wind up with a bunch of
> > > version strings for drivers for hardware you don't have.
> > >
> >
> > Given that boot tracing is best done with initcall_debug and
> > drivers that care about their version string can report it through
> > /sys/modules/<driver>/version why should version string be printed at
> > load time at all?
>
> not every driver provides that file (btw, I guess you mean
> /sys/module, don't you?) there anyway so it's still inconsistent.

Yes, you are right, we drop version string when !MODULE. We need to
keep it if we want to have consistent sysfs data.

> what if you can see up until loading of the driver and it halts there
> without /sys being mounted yet. I don't think you can rely on sysfs
> being mounted or modules being loaded.

Right, so you boot with debug_initcall to see what was the last thing
that we tried to initialize. Hmm, we might need to add debug_modcall
to print names of modules being loaded as well.

-- 
Dmitry
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