🚀 go-pugleaf

In article <1992Nov16.212802.8912@black.ox.ac.uk>, u91pag@ecs.ox.ac.uk (Paul Gilkerson) writes:
[ Tried hacking the FreeSpace module to handle his IDEFS ]

> What I want to know is if there is anyone out there who knows anything
> about showfree and how it works, or if anyone has solved the same
> problem before.

The FreeSpace module knows, initially, how to deal with ADFS, RAMFS, NETFS,
NFS and SCSIFS. Other filing systems have to register by calling:

SWI Free_Register
  r0 = Filing system number
  r1 = Address of handler routine
  r2 = r12 on entry to handler routine

...and deregister by calling:

SWI Free_DeRegister
  r0 = Filing system number

The handler routine is called with:
  r0 = 0      - No-op (just return)
       1      - Get device name
                r0 <- 1
                r1 <- FS number
                r2 <- Buffer for result
                r3 <- Device name / id
                r0 -> length of name
                r1 preserved
                r2 preserved
                r3 preserved
       2      - Get free space for device
                r0 <- 2
                r1 <- FS number
                r2 <- Buffer
                r3 <- Device name / id
                r0-r3 preserved, or r2=0 for free space not changed
                [r2] should be set to total device size
                [r2,4]  "  "  free space
                [r2,8]  "  "  used space
       3      - Compare device
                r0 <- 3
                r1 <- FS number
                r2 <- filename
                r3 <- Device id
                r6 <- Special field
                r0-3,r6 preserved
                Z is set on exit if r2,r6 indicate a file on device r3, clear
                otherwise.

Now - whether or not you can use that to build a free-space monitor for your
IDEFS is a different matter, of course. (-8

--Clive.