HAL_ChibiOS: support uncompressed bootloader on f103-periph

this allows update with very low memory

libraries/AP_HAL_ChibiOS/Util.cpp

@@ -233,7 +233,7 @@ bool Util::flash_bootloader()
 
     EXPECT_DELAY_MS(11000);
 
-    uint8_t *fw = AP_ROMFS::find_decompress(fw_name, fw_size);
+    const uint8_t *fw = AP_ROMFS::find_decompress(fw_name, fw_size);
     if (!fw) {
         hal.console->printf("failed to find %s\n", fw_name);
         return false;
@@ -242,14 +242,14 @@ bool Util::flash_bootloader()
     const uint32_t addr = hal.flash->getpageaddr(0);
     if (!memcmp(fw, (const void*)addr, fw_size)) {
         hal.console->printf("Bootloader up-to-date\n");
-        free(fw);
+        AP_ROMFS::free(fw);
         return true;
     }
 
     hal.console->printf("Erasing\n");
     if (!hal.flash->erasepage(0)) {
         hal.console->printf("Erase failed\n");
-        free(fw);
+        AP_ROMFS::free(fw);
         return false;
     }
     hal.console->printf("Flashing %s @%08x\n", fw_name, (unsigned int)addr);
@@ -264,12 +264,12 @@ bool Util::flash_bootloader()
             continue;
         }
         hal.console->printf("Flash OK\n");
-        free(fw);
+        AP_ROMFS::free(fw);
         return true;
     }
 
     hal.console->printf("Flash failed after %u attempts\n", max_attempts);
-    free(fw);
+    AP_ROMFS::free(fw);
     return false;
 }
 #endif // !HAL_NO_FLASH_SUPPORT && !HAL_NO_ROMFS_SUPPORT

libraries/AP_HAL_ChibiOS/hwdef/f103-periph/hwdef.dat

@@ -146,3 +146,7 @@ env APP_DESCRIPTOR MissionPlanner
 RAM_RESERVE_START 256
 
 # define CH_DBG_ENABLE_STACK_CHECK TRUE
+
+# keep ROMFS uncompressed as we don't have enough RAM
+# to uncompress the bootloader at runtime
+env ROMFS_UNCOMPRESSED True

libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py

@@ -673,6 +673,8 @@ def write_mcu_config(f):
 #define HAL_USE_I2C FALSE
 #define HAL_USE_PWM FALSE
 ''')
+    if env_vars.get('ROMFS_UNCOMPRESSED', False):
+        f.write('#define HAL_ROMFS_UNCOMPRESSED\n')
 
 def write_ldscript(fname):
     '''write ldscript.ld for this board'''