Add 512k (no SPIFFS) build option (#862)

Author: igrr

hardware/esp8266com/esp8266/boards.txt

@@ -65,13 +65,18 @@ generic.menu.UploadSpeed.512000.upload.speed=512000
 generic.menu.UploadSpeed.921600=921600
 generic.menu.UploadSpeed.921600.upload.speed=921600
 
-generic.menu.FlashSize.512K=512K (64K SPIFFS)
-generic.menu.FlashSize.512K.build.flash_size=512K
-generic.menu.FlashSize.512K.build.flash_ld=eagle.flash.512k.ld
-generic.menu.FlashSize.512K.build.spiffs_start=0x6B000
-generic.menu.FlashSize.512K.build.spiffs_end=0x7B000
-generic.menu.FlashSize.512K.build.spiffs_blocksize=4096
-generic.menu.FlashSize.512K.upload.maximum_size=434160
+generic.menu.FlashSize.512K64=512K (64K SPIFFS)
+generic.menu.FlashSize.512K64.build.flash_size=512K
+generic.menu.FlashSize.512K64.build.flash_ld=eagle.flash.512k64.ld
+generic.menu.FlashSize.512K64.build.spiffs_start=0x6B000
+generic.menu.FlashSize.512K64.build.spiffs_end=0x7B000
+generic.menu.FlashSize.512K64.build.spiffs_blocksize=4096
+generic.menu.FlashSize.512K64.upload.maximum_size=434160
+
+generic.menu.FlashSize.512K0=512K (no SPIFFS)
+generic.menu.FlashSize.512K0.build.flash_size=512K
+generic.menu.FlashSize.512K0.build.flash_ld=eagle.flash.512k0.ld
+generic.menu.FlashSize.512K0.upload.maximum_size=499696
 
 generic.menu.FlashSize.1M512=1M (512K SPIFFS)
 generic.menu.FlashSize.1M512.build.flash_size=1M
@@ -410,7 +415,7 @@ thing.build.variant=thing
 thing.build.flash_mode=qio
 # flash chip: AT25SF041 (512 kbyte, 4Mbit)
 thing.build.flash_size=512K
-thing.build.flash_ld=eagle.flash.512k.ld
+thing.build.flash_ld=eagle.flash.512k64.ld
 thing.build.flash_freq=40
 thing.build.spiffs_start=0x6B000
 thing.build.spiffs_end=0x7B000
@@ -526,7 +531,7 @@ esp210.menu.FlashSize.4M1M.build.spiffs_pagesize=256
 # wifio.build.flash_mode=qio
 # wifio.build.flash_size=512K
 # wifio.build.flash_freq=40
-# wifio.build.flash_ld=eagle.flash.512k.ld
+# wifio.build.flash_ld=eagle.flash.512k64.ld
 # wifio.build.spiffs_start=0x6B000
 # wifio.build.spiffs_end=0x7B000
 #

hardware/esp8266com/esp8266/cores/esp8266/spiffs_api.cpp

@@ -100,6 +100,10 @@ class SPIFFSImpl : public FSImpl {
         if (SPIFFS_mounted(&_fs) != 0) {
             return true;
         }
+        if (_size == 0) {
+            DEBUGV("SPIFFS size is zero");
+            return false;
+        }
         if (_tryMount()) {
             return true;
         }
@@ -112,6 +116,11 @@ class SPIFFSImpl : public FSImpl {
     }
 
     bool format() override {
+        if (_size == 0) {
+            DEBUGV("SPIFFS size is zero");
+            return false;
+        }
+
         bool wasMounted = (SPIFFS_mounted(&_fs) != 0);
 
         if (_tryMount()) {

hardware/esp8266com/esp8266/tools/sdk/ld/eagle.flash.512k0.ld

@@ -0,0 +1,18 @@
+/* Flash Split for 512K chips, no SPIFFS */
+/* sketch 487KB */
+/* eeprom 20KB */
+
+MEMORY
+{
+  dport0_0_seg :                        org = 0x3FF00000, len = 0x10
+  dram0_0_seg :                         org = 0x3FFE8000, len = 0x14000
+  iram1_0_seg :                         org = 0x40100000, len = 0x8000
+  irom0_0_seg :                         org = 0x40201010, len = 0x79ff0
+}
+
+PROVIDE ( _SPIFFS_start = 0 );
+PROVIDE ( _SPIFFS_end = 0 );
+PROVIDE ( _SPIFFS_page = 0 );
+PROVIDE ( _SPIFFS_block = 0 );
+
+INCLUDE "../ld/eagle.app.v6.common.ld"