Userdata export: export settings on a FAT16 filesystem.

software/sys_controller/Makefile

@@ -159,6 +159,7 @@ C_SRCS += ossc/av_controller.c
 C_SRCS += ossc/avconfig.c
 C_SRCS += ossc/controls.c
 C_SRCS += ossc/firmware.c
+C_SRCS += ossc/fat16_export.c
 ifeq ($(OSDLANG),JP)
 C_SRCS += ossc/menu_sjis.c
 else

software/sys_controller/ossc/fat16_export.c

@@ -0,0 +1,138 @@
+//
+// Copyright (C) 2020 Ari Sundholm <megari@iki.fi>
+//
+// This file has been contributed to the Open Source Scan Converter project
+// developed by Markus Hiienkari Markus Hiienkari <mhiienka@niksula.hut.fi>
+// and other members of the retro gaming community.
+//
+// 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 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#include <string.h>
+#include "fat16_export.h"
+
+/*
+ * The beginning of the boot sector. Will be followed by the BPB.
+ * Offsets 0x000 to 0x00a, inclusive.
+ */
+static const alt_u8 bootsec_before_bpb_16[11] = {
+    0xeb, 0x00, 0x90, 0x4d, 0x53, 0x57, 0x49, 0x4e,  0x34, 0x2e, 0x31,
+/*    ^-----------^--- Maybe zero these? */
+};
+
+/* The BPB will span offsets 0x00b to 0x23, inclusive. Will be generated. */
+
+/*
+ * The rest of the boot sector before the boot code and terminator.
+ * Offsets 0x024 to 0x03d, inclusive.
+ */
+static const alt_u8 bootsec_after_bpb_16[26] = {
+    0x80, 0x00, 0x29, 0xf4, 0xcf, 0xc6, 0x04, 0x4f, 0x53, 0x53, 0x43, 0x50,
+    0x52, 0x4f, 0x46, 0x49, 0x4c, 0x53, 0x46, 0x41, 0x54, 0x31, 0x36, 0x20,
+    0x20, 0x20,
+};
+
+/*
+ * After this, we have the boot code (448 bytes) and sector terminator
+ * (2 bytes). These will be generated.
+ */
+
+/* Generates a FAT16 boot sector.
+ * buf must be at least FAT16_SECTOR_SIZE bytes long,
+ * and is assumed to be pre-zeroed.
+ */
+void generate_boot_sector_16(alt_u8 *const buf) {
+    /* Initial FAT16 boot sector contents. */
+    memcpy(buf, bootsec_before_bpb_16, 11);
+
+    /* BPB */
+    buf[12] = 0x02;
+    buf[13] = 0x04;
+    buf[14] = 0x80;
+    buf[16] = 0x02;
+    buf[18] = 0x08;
+    buf[20] = 0x80;
+    buf[21] = 0xf8;
+    buf[22] = 0x20;
+    buf[24] = 0x3f;
+    buf[26] = 0xff;
+
+    /*
+     * Then the rest of the boot sector.
+     * The boot code is just 448 bytes of 0xf4.
+     */
+    memcpy(buf + 36, bootsec_after_bpb_16, 26);
+    memset(buf + 62, 0xf4, 448);
+    buf[510] = 0x55;
+    buf[511] = 0xaa;
+}
+
+/* The fixed 'preamble' of a FAT on a FAT16 volume. */
+static const alt_u8 fat16_preamble[4] = {
+    0xf8, 0xff, 0xff, 0xff,
+};
+
+#if 0
+/*
+ * To generate each FAT, we need 1040 bytes of memory.
+ * The buffer is assumed to be zeroed out.
+ * XXX: This is a problem!
+ */
+#define FAT16_ALLOC_SIZE 0x420U
+#endif
+
+/*
+ * Generate a FAT.
+ * The buffer is assumed to be zeroed out and have a size of at least
+ * FAT16_SECTOR_SIZE bytes.
+ * The number of clusters already written is given as an argument.
+ * The function returns the total number of clusters written so far.
+ *
+ * The intention is to be able to generate and write the FAT in chunks
+ * that do not exhaust all the remaining RAM.
+ */
+alt_u16 generate_fat16(alt_u8 *const fat, const alt_u16 written) {
+	alt_u16 cur_ofs = 0;
+    const alt_u16 start_cluster = 3U + written;
+    const alt_u16 clusters_to_write = !written
+        ? ((FAT16_SECTOR_SIZE - sizeof(fat16_preamble)) >> FAT16_ENTRY_SHIFT)
+        : (((514U - written) > (512U >> FAT16_ENTRY_SHIFT))
+            ? (512U >> FAT16_ENTRY_SHIFT)
+            : (514U - written));
+    const alt_u16 end_cluster = start_cluster + clusters_to_write;
+
+    if (!written) {
+        memcpy(fat, fat16_preamble, sizeof(fat16_preamble));
+        cur_ofs += sizeof(fat16_preamble);
+    }
+
+    for (alt_u16 cluster = start_cluster; cluster < end_cluster; ++cluster) {
+        /* FAT16 entries are 16-bit little-endian. */
+        fat[cur_ofs++] = cluster & 0xffU;
+        fat[cur_ofs++] = (cluster >> 8U) & 0xffU;
+    }
+
+    /* After the last cluster, write the chain terminator. */
+    if (end_cluster == 514U) {
+    	fat[cur_ofs++] = 0xff;
+    	fat[cur_ofs++] = 0xff;
+    }
+	return end_cluster;
+}
+
+const alt_u8 prof_dirent_16[PROF_DIRENT_16_SIZE] = {
+    0x4f, 0x53, 0x53, 0x43, 0x50, 0x52, 0x4f, 0x46, 0x42, 0x49, 0x4e, 0x20,
+    0x00, 0x8e, 0x04, 0xb5, 0x6f, 0x51, 0x6f, 0x51, 0x00, 0x00, 0x17, 0x89,
+    0x6f, 0x51, 0x02, 0x00, 0x00, 0x00, 0x10, 0x00,
+};

software/sys_controller/ossc/fat16_export.h

@@ -0,0 +1,76 @@
+//
+// Copyright (C) 2020 Ari Sundholm <megari@iki.fi>
+//
+// This file has been contributed to the Open Source Scan Converter project
+// developed by Markus Hiienkari Markus Hiienkari <mhiienka@niksula.hut.fi>
+// and other members of the retro gaming community.
+//
+// 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 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#ifndef FAT16_EXPORT_H_
+#define FAT16_EXPORT_H_
+
+#include "alt_types.h"
+
+/* Use a sector size of 512 bytes. */
+#define FAT16_SECTOR_SIZE 512U
+//#define FAT16_BOOT_SECTOR_SIZE FAT16_SECTOR_SIZE
+
+/* This volume has 2048-byte clusters. */
+#define FAT16_CLUSTER_SIZE 2048U
+
+/* Offsets of the two File Allocation Tables. */
+#define FAT16_1_OFS 0x10000UL
+#define FAT16_2_OFS 0x14000UL
+
+
+/* Each FAT16 entry is a 16-bit little-endian integer. */
+#define FAT16_ENTRY_SIZE 2U
+#define FAT16_ENTRY_SHIFT 1
+
+/* On this volume, each FAT will be 16 kiB in size. */
+#define FAT16_SIZE 0x4000U
+
+/*
+ * Define the properties and contents of the directory entry for the
+ * settings file.
+ */
+#define PROF_DIRENT_16_OFS  0x18000UL
+#define PROF_DIRENT_16_SIZE 32UL
+
+extern const alt_u8 prof_dirent_16[PROF_DIRENT_16_SIZE];
+
+#define PROF_16_DATA_OFS  0x028000UL
+#define PROF_16_DATA_SIZE 0x100000UL
+/* Profile file data starts at offset 0x00028000 */
+/* Profile file data  ends  at offset 0x00128000 */
+/* Profile file data is exactly 1 MiB long. */
+
+
+/* Generate a FAT16 boot sector.
+ * buf must be at least FAT16_BOOT_SECTOR_SIZE bytes long,
+ * and is assumed to be pre-zeroed.
+ */
+void generate_boot_sector_16(alt_u8 *buf);
+
+/*
+ * Generate a FAT of a FAT16 volume.
+ * The buffer is assumed to be zeroed out and have a size of at least 512 bytes.
+ * The number of clusters already written are given as an argument.
+ * The function returns the total number of clusters written so far.
+ */
+alt_u16 generate_fat16(alt_u8 *fat, alt_u16 written);
+
+#endif // FAT16_EXPORT_H_

software/sys_controller/ossc/userdata.c

@@ -21,6 +21,7 @@
 #include <string.h>
 #include <unistd.h>
 #include "userdata.h"
+#include "fat16_export.h"
 #include "flash.h"
 #include "sdcard.h"
 #include "firmware.h"
@@ -413,8 +414,45 @@ eval_button:
     strncpy(menu_row2, "Exporting...", LCD_ROW_LEN+1);
     ui_disp_menu(2);
 
+    /* TODO: write FAT */
+    _Static_assert(SD_BLK_SIZE == FAT16_SECTOR_SIZE, "Sector size mismatch");
+
+    /* Generate and write the boot sector. */
+    memset(databuf, 0, SD_BLK_SIZE); /* Must be at least 512 bytes! */
+    generate_boot_sector_16(databuf);
+    SD_Write(&sdcard_dev, databuf, 0);
+    /* ERROR HANDLING */
+
+    /* Generate and write the file allocation tables. */
+    for (alt_u16 clusters_written = 0, sd_blk_idx = 0;
+        clusters_written < (PROF_16_DATA_SIZE/FAT16_CLUSTER_SIZE);)
+    {
+        alt_u16 count;
+        memset(databuf, 0, SD_BLK_SIZE); /* Must be at least 512 bytes! */
+        count = generate_fat16(databuf, clusters_written);
+        SD_Write(&sdcard_dev, databuf,
+            (FAT16_1_OFS/SD_BLK_SIZE) + sd_blk_idx);
+        /* ERROR HANDLING */
+
+        SD_Write(&sdcard_dev, databuf,
+            (FAT16_2_OFS/SD_BLK_SIZE) + sd_blk_idx);
+        /* ERROR HANDLING */
+
+        ++sd_blk_idx;
+        clusters_written += count;
+    }
+
+    /* Write the directory entry of the settings file. */
+    memset(databuf, 0, SD_BLK_SIZE);
+    memcpy(databuf, prof_dirent_16, PROF_DIRENT_16_SIZE);
+    SD_Write(&sdcard_dev, databuf, PROF_DIRENT_16_OFS/SD_BLK_SIZE);
+    /* ERROR HANDLING */
+
     /* This may wear the SD card a bit more than necessary... */
-    retval = copy_flash_to_sd(USERDATA_OFFSET/PAGESIZE, 512/SD_BLK_SIZE, (MAX_USERDATA_ENTRY + 1) * SECTORSIZE, databuf);
+    retval = copy_flash_to_sd(USERDATA_OFFSET/PAGESIZE,
+        PROF_16_DATA_OFS/SD_BLK_SIZE,
+        (MAX_USERDATA_ENTRY + 1) * SECTORSIZE,
+        databuf);
 
 out:
     SPI_CS_High();