linux-kernel - Re: [17/26] b43: refuse to load unsupported firmware

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Date:	Sat, 19 Nov 2011 19:49:05 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	greg@...ah.com, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	linux-wireless@...r.kernel.org, b43-dev@...ts.infradead.org,
	roman-vl@...a.ua,
	Rafał Miłecki <zajec5@...il.com>
Subject: Re: [17/26] b43: refuse to load unsupported firmware

On Sat, 2011-11-19 at 11:05 -0800, Greg KH wrote:
> On Sat, Nov 19, 2011 at 05:22:10PM +0000, Ben Hutchings wrote:
> > On Fri, 2011-11-18 at 16:02 -0800, Greg KH wrote:
> > > 3.1-stable review patch.  If anyone has any objections, please let me know.
> > > 
> > > ------------------
> > > 
> > > [This patch is supposed to be applied in 3.1 (and maybe older) branches only.]
> > > 
> > > New kernels support newer firmware that users may try to incorrectly use
> > > with older kernels. Display error and explain the problem in such a case
> > > 
> > > Signed-off-by: RafaÅ MiÅecki <zajec5@...il.com>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> > > 
> > > ---
> > >  drivers/net/wireless/b43/main.c |    7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > --- a/drivers/net/wireless/b43/main.c
> > > +++ b/drivers/net/wireless/b43/main.c
> > > @@ -2508,6 +2508,13 @@ static int b43_upload_microcode(struct b
> > >  		b43_print_fw_helptext(dev->wl, 1);
> > >  		err = -EOPNOTSUPP;
> > >  		goto error;
> > > +	} else if (fwrev >= 598) {
> > > +		b43err(dev->wl, "YOUR FIRMWARE IS TOO NEW. Support for "
> > > +		       "firmware 598 and up requires kernel 3.2 or newer. You "
> > > +		       "have to install older firmware or upgrade kernel.\n");
> > > +		b43_print_fw_helptext(dev->wl, 1);
> > > +		err = -EOPNOTSUPP;
> > > +		goto error;
> > [...]
> > 
> > Again, I strongly object to this way of handling the incompatibility.
> > The revision check is fine, but the solution must be to assign a
> > different filename for the newer revisions.  The changes to 3.0/3.1
> > should be deferred until this is resolved.
> 
> You can object, however the driver author and maintainer wants it done
> this way for now, so that's a valid solution that I have to accept.  It
> solves real bugs that people have already hit when running the 3.0 and
> 3.1 kernels.

The revision check fixes a bug, yes.  What I'm concerned about is the
cop-out error message: 'We didn't deal with versioning properly, so you
get to solve the problem.'  It should be possible to reboot between
multiple installed kernel versions without modifying files.

> Propagating a userspace tool change for those systems
> would be much harder, if not impossible, don't you think? It would also
> require a much more intrusive change to the driver infrastructure to
> handle such a proposed change.

It is the new kernel version and firmware files that should be changed,
not the old ones.

There is another option which is to use the /lib/firmware/<kernel-ver>
directories to separate incompatible firmware versions.  That is not
nearly as good as using a API/ABI number in the filename, but it would
work and the error message could suggest it.

Ben.

-- 
Ben Hutchings
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