Re: old linux scsi headers

[Christoph Hellwig <hch@lst.de>]

On Fri, Jan 09, 2015 at 09:38:50AM -0800, Andy Grover wrote:
> Hello glibc people,
>
> This concerns sysdeps/unix/sysv/linux/scsi/{scsi, scsi_ioctl, sg}.h
>
> They define common SCSI values, as well as Linux's SCSI-related ioctls.
>
> Apparently they were copied from the Linux kernel tree back in 1999, so 
> they're pretty stale.
>
> I'm wondering if I should submit a patch to update these to what's current 
> from the Linux tree, or if maybe it wouldn't be better to have users just 
> directly get these as "uapi" headers from the Linux kernel source directly?
>
> The latter method has issues with being a breaking change for code that 
> relies on what's in glibc now, which may or may not be something we can 
> ease, but would ensure the headers would not become stale again in the 
> future.
>
> What do you think about the best way to proceed?

FYI, I'd like to repeat my propsal from the scsi list here, and a
few alternatives:

(1) separate namespaces (my proposal):

 - we add uapi linux/scsi_ioctl.h and linux/sg.h files that just
   add the ioctl defintions and data structures required for them.
 - because they are linux/ instead of scsi/ are not required to keep
   things like the old opcode or SCSI-2 defintions, which glibc
   can keep in the scsi/* wrappers, and hopefully slowly deprecate
   over the long run

(2) just export what we have in the kernel now (Andys patch):

 - add uapi scsi/scsi.h and scsi/scsi_ioctl.h (and scsi/sg.h for v2),
   exporting what we have in them right now, which might be a little
   different from glibc
 - remove glibcs scsi/*.h

(2a)

 - like 2, but only export the ioctls APIs, the other constants
   will go away at this point

(2b)

 - like 2a, but also add defines compatible to glibc under
   #ifndef __KERNEL__ to the uapi headers.