Topic       : TOS - The Operating System
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Version     : tos.hyp (December 19, 2008)
Subject     : Programmieren/Atari
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Compiled on : Atari
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View Ref-File11.5.15.1.4  dfs_drv_close                                         TOS

 Name:        »dfs_drv_close«

 Parameters:

                  d0  =  int mode 
                  a0  =  DMD *d 
               -> d0  =  long errcode 

 Description: The dfs_drv_close function too fulfills two tasks, 
              depending on mode:

              1. mode == 0:
              The DOS_XFS asks the DFS whether the drive may be 
              closed. If this is not permitted, then EACCDN must be 
              returned, else E_OK (required e.g. for Dlock). Opened 
              files were already recognized be the kernel and DOS_XFS, 
              i.e. in that case dfs_drv_close will not be called at 
              all.

              For this reason, generally no altered sector buffers may 
              exist, even those that are currently being read or 
              written (this is always done via files!). In this case 
              it suffices, therefore, always to return an E_OK. Things 
              become more problematic if one uses a write-back cache. 
              With this it may happen that no file is open any more, 
              but a buffer still holds data that have to be written 
              back. The kernel makes a sync call (xfs_sync, which is 
              passed on to dfs_sync) before the inquiry is made; thus 
              no altered buffers ought to exist any more - if they do, 
              then for safety's sake the DFS should return EACCON.

              Das DOS_XFS fragt das DFS, ob das Laufwerk geschlossen 
              werden darf. Wenn dies nicht erlaubt ist, muß EACCDN 
              geliefert werden, sonst E_OK (nötig z.B. für Dlock()). 
              Geöffnete Dateien wurden bereits von Kernel und DOS_XFS 
              erkannt, d.h. in solch einem Fall wird dfs_drv_close 
              überhaupt nicht aufgerufen.

              2. mode == 1:
              The DOS_XFS forces the closing of the drive, the DFS 
              must return E_OK. No caches may be written back, since 
              the drive is already invalid (after a media change has 
              been reported already).

              With Dlock, dfs_drv_close is first called in mode 0, 
              then - if no error has occurred - with mode 1. This 
              strategy will be carried out also even if at some time a 
              mechanism is built in that monitors the eject button of 
              interchangeable-media drives or CD-ROMs, and bars 
              ejection if necessary.

 Group:       Make-up of a DFS

 See also:    MagiC's DFS-concept