Re: [RFC][PATCH 1/2] firmware version management: add firmware_version()

[Martin Langer <martin-langer@gmx.de>]

On Sat, Jul 08, 2006 at 03:49:57PM +0200, Marcel Holtmann wrote:
> Hi Arjan,
> 
> > > It would be good if a driver knows which firmware version will be 
> > > written to the hardware. I'm talking about external firmware files 
> > > claimed by request_firmware(). 
> > > 
> > > We know so many different firmware files for bcm43xx and it becomes 
> > > more and more complicated without some firmware version management.
> > > 
> > > This patch can create the md5sum of a firmware file. Then it looks into 
> > > a table to figure out which version number is assigned to the hashcode.
> > > That table is placed in the driver code and an example for bcm43xx comes 
> > > in my next mail. Any comments?
> > 
> > why does this have to happen on the kernel side? Isn't it a lot easier
> > and better to let the userspace side of things do this work, and even
> > have a userspace file with the md5->version mapping? Or are there some
> > practical considerations that make that hard to impossible?
> 
> I fully agree that we shouldn't put firmware versioning into the kernel
> drivers. The pattern you give to request_firmware() can be mapped to any
> file on the file system. And you also have the link to the device object
> and I prefer you export a sysfs file for the version so that the helper
> application loading the firmware can pick the right file.

Bcm43xx has no helper application to upload the firmware. This is done 
in the driver. It's RAM based hardware without a Flash-ROM. The driver 
has to upload the firmware in the init phase after each reset.

The driver gets a firmware file from /lib/firmware/ without knowing 
which version this is. It's not possible to say enable this in the 
driver if you find a firmware x and disable that if it's only version 
y. That was my motivation to start thinking about firmware versioning.

But in the meantime I think it's a security issue, too. A driver 
should only accept firmware files with certified checksums. I guess it 
would be really difficult to enter a machine by firmware hijacking. So, 
I'm still in hope that this is only a paranoia on my side. But it's 
worth to think about it.


Martin