feat(stm32-common): add SPI flash driver with littlefs support

libs/stm32-common/include/spi-flash.h

@@ -0,0 +1,16 @@
+#ifndef SPI_FLASH_H
+#define SPI_FLASH_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "lfs.h"
+
+const struct lfs_config *get_spi_flash_lfs_config(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SPI_FLASH_H */

libs/stm32-common/meson.build

@@ -8,6 +8,7 @@ stm32_lib_src = files(
   'src' / 'error.c',
   'src' / 'flash.c',
   'src' / 'print.c',
+  'src' / 'spi-flash.c',
 )
 
 stm32_startup_src = files(

libs/stm32-common/src/spi-flash.c

@@ -1,3 +1,5 @@
+#include "spi-flash.h"
+
 #include <stdint.h>
 #include <stdio.h>
 
@@ -10,6 +12,9 @@
 #include "FreeRTOS.h"
 #include "task.h"
 
+// littlefs
+#include "lfs.h"
+
 #define READ_DATA_COMMAND 0x03
 #define READ_SR1_COMMAND 0x05
 #define WRITE_ENABLE_COMMAND 0x06
@@ -35,6 +40,56 @@ static int read(uint32_t address, uint8_t *data, size_t size);
 static int wait_until_ready(void);
 static int write_enable(void);
 
+// Statically allocate buffers for littelfs
+static uint8_t lfs_read_buf[PAGE_SIZE];
+static uint8_t lfs_prog_buf[PAGE_SIZE];
+static uint8_t lfs_lookahead_buf[PAGE_SIZE];
+
+// Functions required by littlefs
+static int spi_flash_read(const struct lfs_config *config, lfs_block_t block,
+                          lfs_off_t offset, void *buffer, lfs_size_t size) {
+  return read(block * config->block_size + offset, buffer, size);
+}
+
+static int spi_flash_prog(const struct lfs_config *config, lfs_block_t block,
+                          lfs_off_t offset, const void *buffer,
+                          lfs_size_t size) {
+  return program(block * config->block_size + offset, (uint8_t *)buffer, size);
+}
+
+static int spi_flash_erase(const struct lfs_config *config, lfs_block_t block) {
+  return erase(block * config->block_size);
+}
+
+static int spi_flash_sync(const struct lfs_config *config) {
+  (void)config;
+  return APP_OK;
+}
+
+static const struct lfs_config lfs_cfg = {
+    // Operations
+    .read = spi_flash_read,
+    .prog = spi_flash_prog,
+    .erase = spi_flash_erase,
+    .sync = spi_flash_sync,
+
+    // Configuration
+    .read_size = 1,
+    .prog_size = 1,
+    .block_size = SECTOR_SIZE,  // Flash is sector-erasable
+    .block_count = SECTOR_COUNT,
+    .block_cycles = 100,  // Optimize for wear leveling
+
+    .cache_size = sizeof(lfs_read_buf),
+    .read_buffer = lfs_read_buf,
+    .prog_buffer = lfs_prog_buf,
+
+    .lookahead_size = sizeof(lfs_lookahead_buf),
+    .lookahead_buffer = lfs_lookahead_buf,
+};
+
+const struct lfs_config *get_spi_flash_lfs_config(void) { return &lfs_cfg; }
+
 static int wait_until_ready(void) {
   common_peripherals_t *peripherals = get_common_peripherals();
   uint8_t cmd = READ_SR1_COMMAND;