linux-kernel - Re: [PATCH 4/4] GenWQE: Increase driver version number

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Date:	Wed, 9 Jul 2014 14:13:29 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Frank Haverkamp <haver@...ux.vnet.ibm.com>
Cc:	Kleber Sacilotto de Souza <klebers@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, schwidefsky@...ibm.com
Subject: Re: [PATCH 4/4] GenWQE: Increase driver version number

On Fri, Jun 06, 2014 at 02:40:35PM +0200, Frank Haverkamp wrote:
> Hi Greg,
> 
> Am Freitag, den 06.06.2014, 14:07 +0200 schrieb Frank Haverkamp:
> > Hi Greg,
> > 
> > Am Donnerstag, den 05.06.2014, 09:00 -0700 schrieb Greg KH:
> > > On Thu, Jun 05, 2014 at 11:23:04AM +0200, Frank Haverkamp wrote:
> > > > Hi Greg,
> > > > 
> > > > Am Mittwoch, den 04.06.2014, 08:54 -0700 schrieb Greg KH:
> > > > > On Wed, Jun 04, 2014 at 10:57:53AM -0300, Kleber Sacilotto de Souza wrote:
> > > > > > Increase genwqe driver version number.
> > > > > > 
> > > > > > Signed-off-by: Kleber Sacilotto de Souza <klebers@...ux.vnet.ibm.com>
> > > > > > ---
> > > > > >  drivers/misc/genwqe/genwqe_driver.h |    2 +-
> > > > > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > > > > 
> > > > > > diff --git a/drivers/misc/genwqe/genwqe_driver.h b/drivers/misc/genwqe/genwqe_driver.h
> > > > > > index cd52631..a506e9a 100644
> > > > > > --- a/drivers/misc/genwqe/genwqe_driver.h
> > > > > > +++ b/drivers/misc/genwqe/genwqe_driver.h
> > > > > > @@ -36,7 +36,7 @@
> > > > > >  #include <asm/byteorder.h>
> > > > > >  #include <linux/genwqe/genwqe_card.h>
> > > > > >  
> > > > > > -#define DRV_VERS_STRING		"2.0.15"
> > > > > > +#define DRV_VERS_STRING		"2.0.21"
> > > > > 
> > > > > Why is this even needed?  Can't you go off of the kernel version number
> > > > > now?  Who needs / wants this number?
> > > > 
> > > > I am aware that if just considering the mainline kernels, we could use
> > > > the kernel version itself for the purpose of identifying which code we
> > > > are running.
> > > 
> > > Which is what you are patching here :)
> > > 
> > > > But in our lab we are running multiple back-ported versions of this
> > > > driver on different Linux distributions using different kernel versions.
> > > 
> > > Then deal with that in the backported code, the upstream kernel doesn't
> > > care about this.
> > > 
> > > > Our user-space software needs to know if the driver has or has not
> > > > bug-fixes or features. For this purpose, we are using this extra number.
> > > 
> > > Why would you rely on a version number for this, shouldn't you be able
> > > to tell with your api what features are present?
> > 
> > For version "2.0.15" there is no automatic recovery for certain
> > problems, for "2.0.21" there is.
> > 
> > I personally use the driver versions sysfs entry if a user complains
> > that something e.g. the recovery is not working right. First thing I am
> > asking for is the version of the code/driver  as part of the debug data.
> > If that is not matching my expectations, I will tell the user to update
> > the code.
> > 
> > In the current example new applications could more gracefully handle
> > failing recovery scenarios by knowing that the old version of the code
> > cannot properly handle certain problems. And it could this without
> > knowing if it is using a driver which is in the mainline tree or if it
> > is a back-ported version.
> > 
> > Therefore I find it much more convenient for us to handle such things
> > and I would kindly ask you to accept patch 4/4.
> > 
> 
> I talked a bit with a colleague about version numbers for kernel
> drivers. He pointed me on to the fact that when other people contribute
> to our code, they will mostly not alter my version number, which is
> certainly ok. That in turn makes it impossible for me to figure out the
> exact code version from my own (internal) version number.
> 
> So at the end it is the kernel version number or maybe the git checksum
> used to build the code what enables me to identify the exact version of
> the code. If this be the case, than I wonder, if we should not remove
> the "version" sysfs entry entirely. I mean, if you reject the update to
> it anyways ;-).

I suggest just removing the version entirely.  I'll take this patch, but
can you send a follow-on one removing it?

thanks,

greg k-h
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