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Diffstat (limited to 'Documentation/filesystems/qnx6.txt')
| -rw-r--r-- | Documentation/filesystems/qnx6.txt | 28 |
1 files changed, 14 insertions, 14 deletions
diff --git a/Documentation/filesystems/qnx6.txt b/Documentation/filesystems/qnx6.txt index 050223ea03c7..e59f2f09f56e 100644 --- a/Documentation/filesystems/qnx6.txt +++ b/Documentation/filesystems/qnx6.txt @@ -17,7 +17,7 @@ concepts of blocks, inodes and directories. On QNX it is possible to create little endian and big endian qnx6 filesystems. This feature makes it possible to create and use a different endianness fs for the target (QNX is used on quite a range of embedded systems) plattform -running on a different endianess. +running on a different endianness. The Linux driver handles endianness transparently. (LE and BE) Blocks @@ -26,7 +26,7 @@ Blocks The space in the device or file is split up into blocks. These are a fixed size of 512, 1024, 2048 or 4096, which is decided when the filesystem is created. -Blockpointers are 32bit, so the maximum space that can be adressed is +Blockpointers are 32bit, so the maximum space that can be addressed is 2^32 * 4096 bytes or 16TB The superblocks @@ -47,16 +47,16 @@ inactive superblock. Each superblock holds a set of root inodes for the different filesystem parts. (Inode, Bitmap and Longfilenames) Each of these root nodes holds information like total size of the stored -data and the adressing levels in that specific tree. -If the level value is 0, up to 16 direct blocks can be adressed by each +data and the addressing levels in that specific tree. +If the level value is 0, up to 16 direct blocks can be addressed by each node. -Level 1 adds an additional indirect adressing level where each indirect -adressing block holds up to blocksize / 4 bytes pointers to data blocks. -Level 2 adds an additional indirect adressig block level (so, already up -to 16 * 256 * 256 = 1048576 blocks that can be adressed by such a tree)a +Level 1 adds an additional indirect addressing level where each indirect +addressing block holds up to blocksize / 4 bytes pointers to data blocks. +Level 2 adds an additional indirect addressing block level (so, already up +to 16 * 256 * 256 = 1048576 blocks that can be addressed by such a tree). Unused block pointers are always set to ~0 - regardless of root node, -indirect adressing blocks or inodes. +indirect addressing blocks or inodes. Data leaves are always on the lowest level. So no data is stored on upper tree levels. @@ -64,7 +64,7 @@ The first Superblock is located at 0x2000. (0x2000 is the bootblock size) The Audi MMI 3G first superblock directly starts at byte 0. Second superblock position can either be calculated from the superblock information (total number of filesystem blocks) or by taking the highest -device address, zeroing the last 3 bytes and then substracting 0x1000 from +device address, zeroing the last 3 bytes and then subtracting 0x1000 from that address. 0x1000 is the size reserved for each superblock - regardless of the @@ -83,8 +83,8 @@ size, number of blocks used, access time, change time and modification time. Object mode field is POSIX format. (which makes things easier) There are also pointers to the first 16 blocks, if the object data can be -adressed with 16 direct blocks. -For more than 16 blocks an indirect adressing in form of another tree is +addressed with 16 direct blocks. +For more than 16 blocks an indirect addressing in form of another tree is used. (scheme is the same as the one used for the superblock root nodes) The filesize is stored 64bit. Inode counting starts with 1. (whilst long @@ -118,13 +118,13 @@ no block pointers and the directory file record pointing to the target file inode. Character and block special devices do not exist in QNX as those files -are handled by the QNX kernel/drivers and created in /dev independant of the +are handled by the QNX kernel/drivers and created in /dev independent of the underlaying filesystem. Long filenames -------------- -Long filenames are stored in a seperate adressing tree. The staring point +Long filenames are stored in a separate addressing tree. The staring point is the longfilename root node in the active superblock. Each data block (tree leaves) holds one long filename. That filename is limited to 510 bytes. The first two starting bytes are used as length field |