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SubjectRe: the userspace side of driverfs
> The main ideal that we're shooting for is to have one ASCII value per
> file. The ASCII part is mandatory, but there will definitely be exceptions
> where we will have an array of or multiple values per file. We want to
> minimize those instances, though. Both for the sake of easy parsing, but
> also for easy formatting within the drivers.

On IA-64, I've got the arch/ia64/kernel/efivars.c module that exports
/proc/efi/vars/{NVRAM-variables}. It violates several rules of /proc
which I'd like to address in 2.5.x via driverfs.
1) It's in /proc but isn't process-related.
2) It exports its data as binary, not ascii.

Proc was chosen because it was simple, didn't require a major/minor
number, showed easily the set of NVRAM variables that were available
without needing a separate program to go and query a /dev/efivars file
to list them; cat and tar are sufficient for making copies of
variables and restoring them back again. These exact features make
driverfs make sense too.

1) is easy to fix. 2) a little less so. The data structure being
exported is a little over 2KB in length; The data is binary (itself a
variable length set of structures each with no ascii representation).
An ascii representation in "%02x" format will be longer than a 4K page
given to fill out and return. Undoubtedly there's a better way to
handle this, and I'm open to suggestions. The thing being exported is

For such cases where the data being exported is really binary,
having a common set of parse/unparse routines would be nice.


Matt Domsch
Sr. Software Engineer, Lead Engineer, Architect
Dell Linux Solutions
Linux on Dell mailing lists @
#1 US Linux Server provider for 2001 and Q1-2/2002! (IDC Aug 2002)

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