fix: address PR review comments

- Add page-boundary and length validation in steami_flash_write_config
- Fix steami_flash_get_size returning absolute address instead of relative size
- Separate bad-parameters error from flash-write failure in TASK_WRITE_CONFIG
- Update doc to reflect actual 28-byte max payload via I2C protocol
- Document fixed 31-byte frame layout for WRITE_CONFIG command

Author: nedseb

source/board/steami/steami32.c

@@ -440,7 +440,11 @@ void process_task()
                 if( task_rx_len >= 3 ){
                     uint16_t offset = ((uint16_t)task_rx[0] << 8) | task_rx[1];
                     uint16_t len = task_rx[2];
-                    if( len <= task_rx_len - 3 && steami_flash_write_config(offset, task_rx + 3, len) ){
+                    if( len > task_rx_len - 3 ){
+                        error_status_bad_parameter(&status_error);
+                        steami_uart_write_string("ERROR Bad config write parameters.\n");
+                    }
+                    else if( steami_flash_write_config(offset, task_rx + 3, len) ){
                         steami_uart_write_string("Config written.\n");
                     }
                     else{

source/board/steami/steami_flash.c

@@ -138,7 +138,7 @@ uint32_t steami_flash_get_size(){
 
         for(uint16_t i = 0; i < STEAMI_FLASH_MAX_DATA_SIZE; ++i){
             if( data[i] == 0xFF ){
-                return STEAMI_FLASH_FILE_ADDR + offset + i;
+                return offset + i;
             }
         }
 
@@ -234,9 +234,15 @@ bool steami_flash_erase_config(){
 }
 
 bool steami_flash_write_config(uint16_t offset, uint8_t* data, uint16_t len){
+    if( len == 0 || len > 256 ){
+        return false;
+    }
     if( offset + len > STEAMI_FLASH_CONFIG_SIZE ){
         return false;
     }
+    if( (offset % 256) + len > 256 ){
+        return false;
+    }
 
     steami_led_turn_on_blue();
 

source/board/steami/steami_flash.h

@@ -124,7 +124,7 @@ bool steami_flash_erase_config();
  *
  * @param offset byte offset within the config zone (0-4095)
  * @param data data array
- * @param len number of bytes to write (max 256 per call, must stay within one page)
+ * @param len number of bytes to write (max 28 per call via I2C, must stay within one 256-byte page)
  * @return TRUE if successful, FALSE otherwise
  */
 bool steami_flash_write_config(uint16_t offset, uint8_t* data, uint16_t len);

source/board/steami/steami_i2c.c

@@ -69,7 +69,7 @@ static uint16_t get_argument_byte_number(uint8_t cmd){
             return 2;
 
         case WRITE_CONFIG:
-            return 31;
+            return 31;  /* fixed frame: [offset_hi, offset_lo, len, data(28 bytes max)] */
 
         case READ_CONFIG:
             return 2;