Do some housekeeping with fat.h and SECTOR_SIZE

Many includes of fat.h are pointless. Some includes are just for
SECTOR_SIZE. Add a file 'firmware/include/fs_defines.h' for that
and to define tuneable values that were scattered amongst various
headers.

Remove some local definitions of SECTOR_SIZE since they have to be
in agreement with the rest of the fs code anyway.

(We'll see what's in fact pointless in a moment ;)

Change-Id: I9ba183bf58bd87f5c45eba7bd675c7e2c1c18ed5

firmware/include/fs_defines.h

@@ -0,0 +1,108 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2017 by Michael Sevakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#ifndef FS_DEFINES_H
+#define FS_DEFINES_H
+
+/** Tuneable parameters **/
+
+#if 0
+/* Define this just in case you're doing something that may crash a lot and
+   want less write caching */
+#define FS_MIN_WRITECACHING
+#endif
+
+#ifndef MAX_PATH
+#define MAX_PATH        260
+#endif
+
+#define MAX_COMPNAME    260
+
+/* still experimental? */
+/* increasing this will increase the total memory used by the cache; the
+   cache, as noted in disk_cache.h, has other minimum requirements that may
+   prevent reducing its number of entries in order to compensate */
+#ifndef SECTOR_SIZE
+#define SECTOR_SIZE     512
+#endif
+
+/* limits for number of open descriptors - if you increase these values, make
+   certain that the disk cache has enough available buffers */
+#define MAX_OPEN_FILES  11
+#define MAX_OPEN_DIRS   12
+
+/* internal functions open streams as well; make sure they don't fail if all
+   user descs are busy; this needs to be at least the greatest quantity needed
+   at once by all internal functions */
+#ifdef HAVE_DIRCACHE
+#define AUX_FILEOBJS 3
+#else
+#define AUX_FILEOBJS 2
+#endif
+
+/* number of components statically allocated to handle the vast majority
+   of path depths; should maybe be tuned for >= 90th percentile but for now,
+   imma just guessing based on something like:
+        root + 'Music' + 'Artist' + 'Album' + 'Disc N' + filename */
+#define STATIC_PATHCOMP_NUM 6
+
+/* unsigned value that will also hold the off_t range we need without
+   overflow */
+#define file_size_t uint32_t
+
+#ifdef __USE_FILE_OFFSET64
+/* if we want, we can deal with files up to 2^32-1 bytes-- the full FAT16/32
+   range */
+#define FILE_SIZE_MAX   (0xffffffffu)
+#else
+/* file contents and size will be preserved by the APIs so long as ftruncate()
+   isn't used; bytes passed 2^31-1 will not accessible nor will writes succeed
+   that would extend the file beyond the max for a 32-bit off_t */
+#define FILE_SIZE_MAX   (0x7fffffffu)
+#endif
+
+/* if file is "large(ish)", then get rid of the contents now rather than
+   lazily when the file is synced or closed in order to free-up space */
+#define O_TRUNC_THRESH 65536
+
+/* This needs enough for all file handles to have a buffer in the worst case
+ * plus at least one reserved exclusively for the cache client and a couple
+ * for other file system code. The buffers are put to use by the cache if not
+ * taken for another purpose (meaning nothing is wasted sitting fallow).
+ *
+ * One map per volume is maintained in order to avoid collisions between
+ * volumes that would slow cache probing. IOC_MAP_NUM_ENTRIES is the number
+ * for each map per volume. The buffers themselves are shared.
+ */
+#if MEMORYSIZE < 8
+#define DC_NUM_ENTRIES      32
+#define DC_MAP_NUM_ENTRIES  128
+#elif MEMORYSIZE <= 32
+#define DC_NUM_ENTRIES      48
+#define DC_MAP_NUM_ENTRIES  128
+#else /* MEMORYSIZE > 32 */
+#define DC_NUM_ENTRIES      64
+#define DC_MAP_NUM_ENTRIES  256
+#endif /* MEMORYSIZE */
+
+/* this _could_ be larger than a sector if that would ever be useful */
+#define DC_CACHE_BUFSIZE    SECTOR_SIZE
+
+#endif /* FS_DEFINES_H */