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Diffstat (limited to 'Documentation/filesystems/fat_cvf.txt')
| -rw-r--r-- | Documentation/filesystems/fat_cvf.txt | 54 |
1 files changed, 37 insertions, 17 deletions
diff --git a/Documentation/filesystems/fat_cvf.txt b/Documentation/filesystems/fat_cvf.txt index 7eef569b6..c1cf27bd7 100644 --- a/Documentation/filesystems/fat_cvf.txt +++ b/Documentation/filesystems/fat_cvf.txt @@ -1,4 +1,4 @@ -This is the main documentation for the CVF-FAT filesystem extension. 31DEC1997 +This is the main documentation for the CVF-FAT filesystem extension. 18Nov1998 Table of Contents: @@ -37,14 +37,9 @@ like compression and decompression silently. CVF filesystems cannot do bmap. It's impossible in principle. Thus all actions that require bmap do not work (swapping, writable mmapping). Read-only mmapping works because the FAT driver has a hack for this - situation :) Well, with some tricks writable mmapping could work, - (proof: they did under old dmsdos), but..... (hint: readpage/writepage - interface functions) ...... but the FAT driver has to support them - first without bmap :-) - - We'll see. If someone points me to an application that needs this, I - might be persuaded to implement it :). CVF-FAT is already prepared - for using readpage. + situation :) Well, writable mmapping should now work using the readpage + interface function which has been hacked into the FAT driver just for + CVF-FAT :) - attention, DOSEmu users @@ -66,11 +61,28 @@ driver's standard options: cvf_format=xxx Forces the driver to use the CVF module "xxx" instead of auto-detection. - This is only necessary if the CVF format is not recognized correctly + Without this option, the CVF-FAT interface asks all currently loaded + CVF modules whether they recognize the CVF. Therefore, this option is + only necessary if the CVF format is not recognized correctly because of bugs or incompatibilities in the CVF modules. (It skips the detect_cvf call.) "xxx" may be the text "none" (without the quotes) to inhibit using any of the loaded CVF modules, just in case a CVF - module insists on mounting plain FAT filesystems by misunderstanding :) + module insists on mounting plain FAT filesystems by misunderstanding. + "xxx" may also be the text "autoload", which has a special meaning for + a module loader, but does not skip auto-detection. + + If the kernel supports kmod, the cvf_format=xxx option also controls + on-demand CVF module loading. Without this option, nothing is loaded + on demand. With cvf_format=xxx, a module "xxx" is requested automatically + before mounting the compressed filesystem (unless "xxx" is "none"). In + case there is a difference between the CVF format name and the module + name, setup aliases in your modules configuration. If the string "xxx" + is "autoload", a non-existent module "cvf_autoload" is requested which + can be used together with a special modules configuration (alias and + pre-install statements) in order to load more than one CVF module, let + them detect automatically which kind of CVF is to be mounted, and only + keep the "right" module in memory. For examples please refer to the + dmsdos documentation (ftp and http addresses see below). cvf_options=yyy Option string passed to the CVF module. I.e. only the "yyy" is passed @@ -80,8 +92,8 @@ driver's standard options: misinterpretation by the FAT driver, which would recognize the text after a comma as a FAT driver option and might get confused or print strange error messages. The documentation for the CVF module should - offer a different separation symbol, for example the dot ".", which - is only valid inside the string "yyy". + offer a different separation symbol, for example the dot "." or the + plus sign "+", which is only valid inside the string "yyy". 4. Description of the CVF-FAT interface @@ -120,11 +132,11 @@ It contains... is set, mmap is set to generic_file_mmap and readpage is caught and redirected to the cvf_readpage function. If it is not set, readpage is set to generic_readpage and mmap is caught and redirected - to cvf_mmap. + to cvf_mmap. (If you want writable mmap use the readpage interface.) - detect_cvf: A function that is called to decide whether the filesystem is a CVF of the type the module supports. The detect_cvf function must return 0 - for "NO, I DON'T KNOW THIS GARBAGE" or anything !=0 for "YES, THIS IS + for "NO, I DON'T KNOW THIS GARBAGE" or anything >0 for "YES, THIS IS THE KIND OF CVF I SUPPORT". The function must maintain the module usage counters for safety, i.e. do MOD_INC_USE_COUNT at the beginning and MOD_DEC_USE_COUNT at the end. The function *must not* assume that @@ -180,11 +192,19 @@ int unregister_cvf_format(struct cvf_format*cvf_format); that has not been previously registered. The code uses the version id to distinguish the modules, so be sure to keep it unique. -5. CVS Modules +5. CVF Modules ------------------------------------------------------------------------------ Refer to the dmsdos module (the successor of the dmsdos filesystem) for a sample implementation. It can currently be found at - ftp://fb9nt.uni-duisburg.de/pub/linux/dmsdos + ftp://fb9nt.uni-duisburg.de/pub/linux/dmsdos/dmsdos-x.y.z.tgz + ftp://sunsite.unc.edu/pub/Linux/system/Filesystems/dosfs/dmsdos-x.y.z.tgz + ftp://ftp.uni-stuttgart.de/pub/systems/linux/local/system/dmsdos-x.y.z.tgz + +(where x.y.z is to be replaced with the actual version number). Full +documentation about dmsdos is included in the dmsdos package, but can also +be found at + http://fb9nt.uni-duisburg.de/mitarbeiter/gockel/software/dmsdos/index.html + http://www.yk.rim.or.jp/~takafumi/dmsdos/index.html (in Japanese). |