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  1. /*
  2.  * Copyright (c) 2008 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup fs
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    fat_ops.c
  35.  * @brief   Implementation of VFS operations for the FAT file system server.
  36.  */
  37.  
  38. #include "fat.h"
  39. #include "../../vfs/vfs.h"
  40. #include <libfs.h>
  41. #include <ipc/ipc.h>
  42. #include <ipc/services.h>
  43. #include <ipc/devmap.h>
  44. #include <async.h>
  45. #include <errno.h>
  46. #include <string.h>
  47. #include <byteorder.h>
  48. #include <libadt/hash_table.h>
  49. #include <libadt/list.h>
  50. #include <assert.h>
  51. #include <futex.h>
  52. #include <sys/mman.h>
  53.  
  54. #define BS_BLOCK        0
  55. #define BS_SIZE         512
  56.  
  57. /** Futex protecting the list of cached free FAT nodes. */
  58. static futex_t ffn_futex = FUTEX_INITIALIZER;
  59.  
  60. /** List of cached free FAT nodes. */
  61. static LIST_INITIALIZE(ffn_head);
  62.  
  63. #define FAT_NAME_LEN        8
  64. #define FAT_EXT_LEN     3
  65.  
  66. #define FAT_PAD         ' '
  67.  
  68. #define FAT_DENTRY_UNUSED   0x00
  69. #define FAT_DENTRY_E5_ESC   0x05
  70. #define FAT_DENTRY_DOT      0x2e
  71. #define FAT_DENTRY_ERASED   0xe5
  72.  
  73. #define min(a, b)       ((a) < (b) ? (a) : (b))
  74.  
  75. static void dentry_name_canonify(fat_dentry_t *d, char *buf)
  76. {
  77.     int i;
  78.  
  79.     for (i = 0; i < FAT_NAME_LEN; i++) {
  80.         if (d->name[i] == FAT_PAD)
  81.             break;
  82.         if (d->name[i] == FAT_DENTRY_E5_ESC)
  83.             *buf++ = 0xe5;
  84.         else
  85.             *buf++ = d->name[i];
  86.     }
  87.     if (d->ext[0] != FAT_PAD)
  88.         *buf++ = '.';
  89.     for (i = 0; i < FAT_EXT_LEN; i++) {
  90.         if (d->ext[i] == FAT_PAD) {
  91.             *buf = '\0';
  92.             return;
  93.         }
  94.         if (d->ext[i] == FAT_DENTRY_E5_ESC)
  95.             *buf++ = 0xe5;
  96.         else
  97.             *buf++ = d->ext[i];
  98.     }
  99.     *buf = '\0';
  100. }
  101.  
  102. static int dev_phone = -1;      /* FIXME */
  103. static void *dev_buffer = NULL;     /* FIXME */
  104.  
  105. /* TODO move somewhere else */
  106. typedef struct {
  107.     void *data;
  108.     size_t size;
  109. } block_t;
  110.  
  111. static block_t *block_get(dev_handle_t dev_handle, off_t offset, size_t bs)
  112. {
  113.     /* FIXME */
  114.     block_t *b;
  115.     off_t bufpos = 0;
  116.     size_t buflen = 0;
  117.     off_t pos = offset * bs;
  118.  
  119.     assert(dev_phone != -1);
  120.     assert(dev_buffer);
  121.  
  122.     b = malloc(sizeof(block_t));
  123.     if (!b)
  124.         return NULL;
  125.    
  126.     b->data = malloc(bs);
  127.     if (!b->data) {
  128.         free(b);
  129.         return NULL;
  130.     }
  131.     b->size = bs;
  132.  
  133.     if (!libfs_blockread(dev_phone, dev_buffer, &bufpos, &buflen, &pos,
  134.         b->data, bs, bs)) {
  135.         free(b->data);
  136.         free(b);
  137.         return NULL;
  138.     }
  139.  
  140.     return b;
  141. }
  142.  
  143. static void block_put(block_t *block)
  144. {
  145.     /* FIXME */
  146.     free(block->data);
  147.     free(block);
  148. }
  149.  
  150. #define FAT_BS(b)       ((fat_bs_t *)((b)->data))
  151.  
  152. #define FAT_CLST_RES0   0x0000
  153. #define FAT_CLST_RES1   0x0001
  154. #define FAT_CLST_FIRST  0x0002
  155. #define FAT_CLST_BAD    0xfff7
  156. #define FAT_CLST_LAST1  0xfff8
  157. #define FAT_CLST_LAST8  0xffff
  158.  
  159. /* internally used to mark root directory's parent */
  160. #define FAT_CLST_ROOTPAR    FAT_CLST_RES0
  161. /* internally used to mark root directory */
  162. #define FAT_CLST_ROOT       FAT_CLST_RES1
  163.  
  164. #define fat_block_get(np, off) \
  165.     _fat_block_get((np)->idx->dev_handle, (np)->firstc, (off))
  166.  
  167. static block_t *
  168. _fat_block_get(dev_handle_t dev_handle, fat_cluster_t firstc, off_t offset)
  169. {
  170.     block_t *bb;
  171.     block_t *b;
  172.     unsigned bps;
  173.     unsigned spc;
  174.     unsigned rscnt;     /* block address of the first FAT */
  175.     unsigned fatcnt;
  176.     unsigned rde;
  177.     unsigned rds;       /* root directory size */
  178.     unsigned sf;
  179.     unsigned ssa;       /* size of the system area */
  180.     unsigned clusters;
  181.     fat_cluster_t clst = firstc;
  182.     unsigned i;
  183.  
  184.     bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
  185.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  186.     spc = FAT_BS(bb)->spc;
  187.     rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);
  188.     fatcnt = FAT_BS(bb)->fatcnt;
  189.     rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);
  190.     sf = uint16_t_le2host(FAT_BS(bb)->sec_per_fat);
  191.     block_put(bb);
  192.  
  193.     rds = (sizeof(fat_dentry_t) * rde) / bps;
  194.     rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
  195.     ssa = rscnt + fatcnt * sf + rds;
  196.  
  197.     if (firstc == FAT_CLST_ROOT) {
  198.         /* root directory special case */
  199.         assert(offset < rds);
  200.         b = block_get(dev_handle, rscnt + fatcnt * sf + offset, bps);
  201.         return b;
  202.     }
  203.  
  204.     clusters = offset / spc;
  205.     for (i = 0; i < clusters; i++) {
  206.         unsigned fsec;  /* sector offset relative to FAT1 */
  207.         unsigned fidx;  /* FAT1 entry index */
  208.  
  209.         assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);
  210.         fsec = (clst * sizeof(fat_cluster_t)) / bps;
  211.         fidx = clst % (bps / sizeof(fat_cluster_t));
  212.         /* read FAT1 */
  213.         b = block_get(dev_handle, rscnt + fsec, bps);
  214.         clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
  215.         assert(clst != FAT_CLST_BAD);
  216.         assert(clst < FAT_CLST_LAST1);
  217.         block_put(b);
  218.     }
  219.  
  220.     b = block_get(dev_handle, ssa + (clst - FAT_CLST_FIRST) * spc +
  221.         offset % spc, bps);
  222.  
  223.     return b;
  224. }
  225.  
  226. static void fat_node_initialize(fat_node_t *node)
  227. {
  228.     futex_initialize(&node->lock, 1);
  229.     node->idx = NULL;
  230.     node->type = 0;
  231.     link_initialize(&node->ffn_link);
  232.     node->size = 0;
  233.     node->lnkcnt = 0;
  234.     node->refcnt = 0;
  235.     node->dirty = false;
  236. }
  237.  
  238. static uint16_t fat_bps_get(dev_handle_t dev_handle)
  239. {
  240.     block_t *bb;
  241.     uint16_t bps;
  242.    
  243.     bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
  244.     assert(bb != NULL);
  245.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  246.     block_put(bb);
  247.  
  248.     return bps;
  249. }
  250.  
  251. typedef enum {
  252.     FAT_DENTRY_SKIP,
  253.     FAT_DENTRY_LAST,
  254.     FAT_DENTRY_VALID
  255. } fat_dentry_clsf_t;
  256.  
  257. static fat_dentry_clsf_t fat_classify_dentry(fat_dentry_t *d)
  258. {
  259.     if (d->attr & FAT_ATTR_VOLLABEL) {
  260.         /* volume label entry */
  261.         return FAT_DENTRY_SKIP;
  262.     }
  263.     if (d->name[0] == FAT_DENTRY_ERASED) {
  264.         /* not-currently-used entry */
  265.         return FAT_DENTRY_SKIP;
  266.     }
  267.     if (d->name[0] == FAT_DENTRY_UNUSED) {
  268.         /* never used entry */
  269.         return FAT_DENTRY_LAST;
  270.     }
  271.     if (d->name[0] == FAT_DENTRY_DOT) {
  272.         /*
  273.          * Most likely '.' or '..'.
  274.          * It cannot occur in a regular file name.
  275.          */
  276.         return FAT_DENTRY_SKIP;
  277.     }
  278.     return FAT_DENTRY_VALID;
  279. }
  280.  
  281. static void fat_node_sync(fat_node_t *node)
  282. {
  283.     /* TODO */
  284. }
  285.  
  286. /** Internal version of fat_node_get().
  287.  *
  288.  * @param idxp      Locked index structure.
  289.  */
  290. static void *fat_node_get_core(fat_idx_t *idxp)
  291. {
  292.     block_t *b;
  293.     fat_dentry_t *d;
  294.     fat_node_t *nodep;
  295.     unsigned bps;
  296.     unsigned dps;
  297.  
  298.     if (idxp->nodep) {
  299.         /*
  300.          * We are lucky.
  301.          * The node is already instantiated in memory.
  302.          */
  303.         futex_down(&idxp->nodep->lock);
  304.         if (!idxp->nodep->refcnt++)
  305.             list_remove(&nodep->ffn_link);
  306.         futex_up(&idxp->nodep->lock);
  307.         return idxp->nodep;
  308.     }
  309.  
  310.     /*
  311.      * We must instantiate the node from the file system.
  312.      */
  313.    
  314.     assert(idxp->pfc);
  315.  
  316.     futex_down(&ffn_futex);
  317.     if (!list_empty(&ffn_head)) {
  318.         /* Try to use a cached free node structure. */
  319.         fat_idx_t *idxp_tmp;
  320.         nodep = list_get_instance(ffn_head.next, fat_node_t, ffn_link);
  321.         if (futex_trydown(&nodep->lock) == ESYNCH_WOULD_BLOCK)
  322.             goto skip_cache;
  323.         idxp_tmp = nodep->idx;
  324.         if (futex_trydown(&idxp_tmp->lock) == ESYNCH_WOULD_BLOCK) {
  325.             futex_up(&nodep->lock);
  326.             goto skip_cache;
  327.         }
  328.         list_remove(&nodep->ffn_link);
  329.         futex_up(&ffn_futex);
  330.         if (nodep->dirty)
  331.             fat_node_sync(nodep);
  332.         idxp_tmp->nodep = NULL;
  333.         futex_up(&nodep->lock);
  334.         futex_up(&idxp_tmp->lock);
  335.     } else {
  336. skip_cache:
  337.         /* Try to allocate a new node structure. */
  338.         futex_up(&ffn_futex);
  339.         nodep = (fat_node_t *)malloc(sizeof(fat_node_t));
  340.         if (!nodep)
  341.             return NULL;
  342.     }
  343.     fat_node_initialize(nodep);
  344.  
  345.     bps = fat_bps_get(idxp->dev_handle);
  346.     dps = bps / sizeof(fat_dentry_t);
  347.  
  348.     /* Read the block that contains the dentry of interest. */
  349.     b = _fat_block_get(idxp->dev_handle, idxp->pfc,
  350.         (idxp->pdi * sizeof(fat_dentry_t)) / bps);
  351.     assert(b);
  352.  
  353.     d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);
  354.     if (d->attr & FAT_ATTR_SUBDIR) {
  355.         /*
  356.          * The only directory which does not have this bit set is the
  357.          * root directory itself. The root directory node is handled
  358.          * and initialized elsewhere.
  359.          */
  360.         nodep->type = FAT_DIRECTORY;
  361.         /*
  362.          * TODO: determine the size by walking FAT. Surprisingly, the
  363.          * 'size' filed of the FAT dentry is not defined for the
  364.          * directory entry type.
  365.          */
  366.         nodep->size = 64 * sizeof(fat_dentry_t);
  367.     } else {
  368.         nodep->type = FAT_FILE;
  369.         nodep->size = uint32_t_le2host(d->size);
  370.     }
  371.     nodep->firstc = uint16_t_le2host(d->firstc);
  372.     nodep->lnkcnt = 1;
  373.     nodep->refcnt = 1;
  374.  
  375.     block_put(b);
  376.  
  377.     /* Link the idx structure with the node structure. */
  378.     nodep->idx = idxp;
  379.     idxp->nodep = nodep;
  380.  
  381.     return nodep;
  382. }
  383.  
  384. /** Instantiate a FAT in-core node. */
  385. static void *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
  386. {
  387.     void *node;
  388.     fat_idx_t *idxp;
  389.  
  390.     idxp = fat_idx_get_by_index(dev_handle, index);
  391.     if (!idxp)
  392.         return NULL;
  393.     /* idxp->lock held */
  394.     node = fat_node_get_core(idxp);
  395.     futex_up(&idxp->lock);
  396.     return node;
  397. }
  398.  
  399. static void fat_node_put(void *node)
  400. {
  401.     fat_node_t *nodep = (fat_node_t *)node;
  402.  
  403.     futex_down(&nodep->lock);
  404.     if (!--nodep->refcnt) {
  405.         futex_down(&ffn_futex);
  406.         list_append(&nodep->ffn_link, &ffn_head);
  407.         futex_up(&ffn_futex);
  408.     }
  409.     futex_up(&nodep->lock);
  410. }
  411.  
  412. static void *fat_create(int flags)
  413. {
  414.     return NULL;    /* not supported at the moment */
  415. }
  416.  
  417. static int fat_destroy(void *node)
  418. {
  419.     return ENOTSUP; /* not supported at the moment */
  420. }
  421.  
  422. static bool fat_link(void *prnt, void *chld, const char *name)
  423. {
  424.     return false;   /* not supported at the moment */
  425. }
  426.  
  427. static int fat_unlink(void *prnt, void *chld)
  428. {
  429.     return ENOTSUP; /* not supported at the moment */
  430. }
  431.  
  432. static void *fat_match(void *prnt, const char *component)
  433. {
  434.     fat_node_t *parentp = (fat_node_t *)prnt;
  435.     char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  436.     unsigned i, j;
  437.     unsigned bps;       /* bytes per sector */
  438.     unsigned dps;       /* dentries per sector */
  439.     unsigned blocks;
  440.     fat_dentry_t *d;
  441.     block_t *b;
  442.  
  443.     futex_down(&parentp->idx->lock);
  444.     bps = fat_bps_get(parentp->idx->dev_handle);
  445.     dps = bps / sizeof(fat_dentry_t);
  446.     blocks = parentp->size / bps + (parentp->size % bps != 0);
  447.     for (i = 0; i < blocks; i++) {
  448.         unsigned dentries;
  449.        
  450.         b = fat_block_get(parentp, i);
  451.         dentries = (i == blocks - 1) ?
  452.             parentp->size % sizeof(fat_dentry_t) :
  453.             dps;
  454.         for (j = 0; j < dentries; j++) {
  455.             d = ((fat_dentry_t *)b->data) + j;
  456.             switch (fat_classify_dentry(d)) {
  457.             case FAT_DENTRY_SKIP:
  458.                 continue;
  459.             case FAT_DENTRY_LAST:
  460.                 block_put(b);
  461.                 futex_up(&parentp->idx->lock);
  462.                 return NULL;
  463.             default:
  464.             case FAT_DENTRY_VALID:
  465.                 dentry_name_canonify(d, name);
  466.                 break;
  467.             }
  468.             if (stricmp(name, component) == 0) {
  469.                 /* hit */
  470.                 void *node;
  471.                 /*
  472.                  * Assume tree hierarchy for locking.  We
  473.                  * already have the parent and now we are going
  474.                  * to lock the child.  Never lock in the oposite
  475.                  * order.
  476.                  */
  477.                 fat_idx_t *idx = fat_idx_get_by_pos(
  478.                     parentp->idx->dev_handle, parentp->firstc,
  479.                     i * dps + j);
  480.                 futex_up(&parentp->idx->lock);
  481.                 if (!idx) {
  482.                     /*
  483.                      * Can happen if memory is low or if we
  484.                      * run out of 32-bit indices.
  485.                      */
  486.                     block_put(b);
  487.                     return NULL;
  488.                 }
  489.                 node = fat_node_get_core(idx);
  490.                 futex_up(&idx->lock);
  491.                 block_put(b);
  492.                 return node;
  493.             }
  494.         }
  495.         block_put(b);
  496.     }
  497.     futex_up(&parentp->idx->lock);
  498.     return NULL;
  499. }
  500.  
  501. static fs_index_t fat_index_get(void *node)
  502. {
  503.     fat_node_t *fnodep = (fat_node_t *)node;
  504.     if (!fnodep)
  505.         return 0;
  506.     return fnodep->idx->index;
  507. }
  508.  
  509. static size_t fat_size_get(void *node)
  510. {
  511.     return ((fat_node_t *)node)->size;
  512. }
  513.  
  514. static unsigned fat_lnkcnt_get(void *node)
  515. {
  516.     return ((fat_node_t *)node)->lnkcnt;
  517. }
  518.  
  519. static bool fat_has_children(void *node)
  520. {
  521.     fat_node_t *nodep = (fat_node_t *)node;
  522.     unsigned bps;
  523.     unsigned dps;
  524.     unsigned blocks;
  525.     block_t *b;
  526.     unsigned i, j;
  527.  
  528.     if (nodep->type != FAT_DIRECTORY)
  529.         return false;
  530.  
  531.     futex_down(&nodep->idx->lock);
  532.     bps = fat_bps_get(nodep->idx->dev_handle);
  533.     dps = bps / sizeof(fat_dentry_t);
  534.  
  535.     blocks = nodep->size / bps + (nodep->size % bps != 0);
  536.  
  537.     for (i = 0; i < blocks; i++) {
  538.         unsigned dentries;
  539.         fat_dentry_t *d;
  540.    
  541.         b = fat_block_get(nodep, i);
  542.         dentries = (i == blocks - 1) ?
  543.             nodep->size % sizeof(fat_dentry_t) :
  544.             dps;
  545.         for (j = 0; j < dentries; j++) {
  546.             d = ((fat_dentry_t *)b->data) + j;
  547.             switch (fat_classify_dentry(d)) {
  548.             case FAT_DENTRY_SKIP:
  549.                 continue;
  550.             case FAT_DENTRY_LAST:
  551.                 block_put(b);
  552.                 futex_up(&nodep->idx->lock);
  553.                 return false;
  554.             default:
  555.             case FAT_DENTRY_VALID:
  556.                 block_put(b);
  557.                 futex_up(&nodep->idx->lock);
  558.                 return true;
  559.             }
  560.             block_put(b);
  561.             futex_up(&nodep->idx->lock);
  562.             return true;
  563.         }
  564.         block_put(b);
  565.     }
  566.  
  567.     futex_up(&nodep->idx->lock);
  568.     return false;
  569. }
  570.  
  571. static void *fat_root_get(dev_handle_t dev_handle)
  572. {
  573.     return fat_node_get(dev_handle, 0);
  574. }
  575.  
  576. static char fat_plb_get_char(unsigned pos)
  577. {
  578.     return fat_reg.plb_ro[pos % PLB_SIZE];
  579. }
  580.  
  581. static bool fat_is_directory(void *node)
  582. {
  583.     return ((fat_node_t *)node)->type == FAT_DIRECTORY;
  584. }
  585.  
  586. static bool fat_is_file(void *node)
  587. {
  588.     return ((fat_node_t *)node)->type == FAT_FILE;
  589. }
  590.  
  591. /** libfs operations */
  592. libfs_ops_t fat_libfs_ops = {
  593.     .match = fat_match,
  594.     .node_get = fat_node_get,
  595.     .node_put = fat_node_put,
  596.     .create = fat_create,
  597.     .destroy = fat_destroy,
  598.     .link = fat_link,
  599.     .unlink = fat_unlink,
  600.     .index_get = fat_index_get,
  601.     .size_get = fat_size_get,
  602.     .lnkcnt_get = fat_lnkcnt_get,
  603.     .has_children = fat_has_children,
  604.     .root_get = fat_root_get,
  605.     .plb_get_char = fat_plb_get_char,
  606.     .is_directory = fat_is_directory,
  607.     .is_file = fat_is_file
  608. };
  609.  
  610. void fat_mounted(ipc_callid_t rid, ipc_call_t *request)
  611. {
  612.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  613.     block_t *bb;
  614.     uint16_t bps;
  615.     uint16_t rde;
  616.     int rc;
  617.  
  618.     /*
  619.      * For now, we don't bother to remember dev_handle, dev_phone or
  620.      * dev_buffer in some data structure. We use global variables because we
  621.      * know there will be at most one mount on this file system.
  622.      * Of course, this is a huge TODO item.
  623.      */
  624.     dev_buffer = mmap(NULL, BS_SIZE, PROTO_READ | PROTO_WRITE,
  625.         MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
  626.    
  627.     if (!dev_buffer) {
  628.         ipc_answer_0(rid, ENOMEM);
  629.         return;
  630.     }
  631.  
  632.     dev_phone = ipc_connect_me_to(PHONE_NS, SERVICE_DEVMAP,
  633.         DEVMAP_CONNECT_TO_DEVICE, dev_handle);
  634.  
  635.     if (dev_phone < 0) {
  636.         munmap(dev_buffer, BS_SIZE);
  637.         ipc_answer_0(rid, dev_phone);
  638.         return;
  639.     }
  640.  
  641.     rc = ipc_share_out_start(dev_phone, dev_buffer,
  642.         AS_AREA_READ | AS_AREA_WRITE);
  643.     if (rc != EOK) {
  644.             munmap(dev_buffer, BS_SIZE);
  645.         ipc_answer_0(rid, rc);
  646.         return;
  647.     }
  648.  
  649.     /* Read the number of root directory entries. */
  650.     bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
  651.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  652.     rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);
  653.     block_put(bb);
  654.  
  655.     if (bps != BS_SIZE) {
  656.         munmap(dev_buffer, BS_SIZE);
  657.         ipc_answer_0(rid, ENOTSUP);
  658.         return;
  659.     }
  660.  
  661.     rc = fat_idx_init_by_dev_handle(dev_handle);
  662.     if (rc != EOK) {
  663.             munmap(dev_buffer, BS_SIZE);
  664.         ipc_answer_0(rid, rc);
  665.         return;
  666.     }
  667.  
  668.     /* Initialize the root node. */
  669.     fat_node_t *rootp = (fat_node_t *)malloc(sizeof(fat_node_t));
  670.     if (!rootp) {
  671.             munmap(dev_buffer, BS_SIZE);
  672.         fat_idx_fini_by_dev_handle(dev_handle);
  673.         ipc_answer_0(rid, ENOMEM);
  674.         return;
  675.     }
  676.     fat_node_initialize(rootp);
  677.  
  678.     fat_idx_t *ridxp = fat_idx_get_by_pos(dev_handle, FAT_CLST_ROOTPAR, 0);
  679.     if (!ridxp) {
  680.             munmap(dev_buffer, BS_SIZE);
  681.         free(rootp);
  682.         fat_idx_fini_by_dev_handle(dev_handle);
  683.         ipc_answer_0(rid, ENOMEM);
  684.         return;
  685.     }
  686.     assert(ridxp->index == 0);
  687.     /* ridxp->lock held */
  688.  
  689.     rootp->type = FAT_DIRECTORY;
  690.     rootp->firstc = FAT_CLST_ROOT;
  691.     rootp->refcnt = 1;
  692.     rootp->size = rde * sizeof(fat_dentry_t);
  693.     rootp->idx = ridxp;
  694.     ridxp->nodep = rootp;
  695.    
  696.     futex_up(&ridxp->lock);
  697.  
  698.     ipc_answer_0(rid, EOK);
  699. }
  700.  
  701. void fat_mount(ipc_callid_t rid, ipc_call_t *request)
  702. {
  703.     ipc_answer_0(rid, ENOTSUP);
  704. }
  705.  
  706. void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
  707. {
  708.     libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  709. }
  710.  
  711. void fat_read(ipc_callid_t rid, ipc_call_t *request)
  712. {
  713.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  714.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  715.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  716.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  717.     uint16_t bps = fat_bps_get(dev_handle);
  718.     size_t bytes;
  719.  
  720.     if (!nodep) {
  721.         ipc_answer_0(rid, ENOENT);
  722.         return;
  723.     }
  724.  
  725.     ipc_callid_t callid;
  726.     size_t len;
  727.     if (!ipc_data_write_receive(&callid, &len)) {
  728.         fat_node_put(nodep);
  729.         ipc_answer_0(callid, EINVAL);
  730.         ipc_answer_0(rid, EINVAL);
  731.         return;
  732.     }
  733.  
  734.     if (nodep->type == FAT_FILE) {
  735.         block_t *b;
  736.  
  737.         bytes = min(len, bps - pos % bps);
  738.         b = fat_block_get(nodep, pos / bps);
  739.         (void) ipc_data_read_finalize(callid, b->data + pos % bps,
  740.             bytes);
  741.         block_put(b);
  742.     } else {
  743.         assert(nodep->type == FAT_DIRECTORY);
  744.         /* TODO */
  745.         fat_node_put(nodep);
  746.         ipc_answer_0(callid, ENOTSUP);
  747.         ipc_answer_0(rid, ENOTSUP);
  748.         return;
  749.     }
  750.  
  751.     fat_node_put(nodep);
  752.     ipc_answer_1(rid, EOK, (ipcarg_t)bytes);
  753. }
  754.  
  755. /**
  756.  * @}
  757.  */
  758.