at25d.c

static bool flash_busy(void) {
	uint8_t cmd = CMD_RDSR;
	uint8_t data;
	spi_tx(config, &cmd, 1, &data , 1, 0);

	return data & STAT_BSY;
}

int flash_erase_block(uint32_t address, block_erase_t mode) {
	uint8_t cmd_buffer[4];

	// enable write
	cmd_buffer[0] = CMD_WREN;
	spi_tx(config, cmd_buffer, 1, 0, 0, 0);

	// erase
	switch (mode) {
	case BLOCK_4K:	// 4K erase
		cmd_buffer[0] = CMD_SE;
		break;
	case BLOCK_32K:	// 32K erase
		cmd_buffer[0] = CMD_BE32;
		break;
	case BLOCK_64K:	// 64K erase
		cmd_buffer[0] = CMD_BE64;
		break;
	case BLOCK_ALL:
		cmd_buffer[0] = CMD_CE;
		break;
	default:
		return -1;
	}

	if (mode == BLOCK_ALL) {
		spi_tx(config, cmd_buffer, 1, 0, 0, 0);
	} else {
		cmd_buffer[1] = (address >> 16) & 0xff;
		cmd_buffer[2] = (address >>  8) & 0xff;
		cmd_buffer[3] = (address >>  0) & 0xff;

		spi_tx(config, cmd_buffer, 4, 0, 0, 0);
	}

	while(flash_busy());

	return 0;
}

int flash_write_page(uint32_t address, uint32_t len, const uint8_t *data) {
	uint8_t cmd_buffer[4];

	// enable write
	cmd_buffer[0] = CMD_WREN;
	spi_tx(config, cmd_buffer, 1, 0, 0, 0);

	// write page
	cmd_buffer[0] = CMD_PP;
	cmd_buffer[1] = (address >> 16) & 0xff;
	cmd_buffer[2] = (address >>  8) & 0xff;
	cmd_buffer[3] = (address >>  0) & 0xff;

	spi_tx(config, cmd_buffer, 4, (uint8_t *) data, len, SPI_DATA_IMMUTABLE);

	while(flash_busy());

	return 0; // spiffs wants it so
}

int flash_read_page(uint32_t address, uint32_t len, uint8_t *data) {
	uint8_t cmd_buffer[5];
	cmd_buffer[0] = CMD_FREAD;
	cmd_buffer[1] = (address >> 16) & 0xff;
	cmd_buffer[2] = (address >>  8) & 0xff;
	cmd_buffer[3] = (address >>  0) & 0xff;
	cmd_buffer[4] = 0;

	spi_tx(config, cmd_buffer, 5, data, len, 0);

	return 0; // spiffs wants it so
}

void flash_init(void) {
	flash_spi_init();

	uint8_t cmd_buffer[2];

	// wait for the device to be ready
	busy_wait(100);

	// write enable (for writing status register)
	cmd_buffer[0] = CMD_WREN;
	spi_tx(config, cmd_buffer, 1, 0, 0, 0);

	// write status reguster
	cmd_buffer[0] = CMD_WRSR;
	cmd_buffer[1] = 0;
	spi_tx(config, cmd_buffer, 2, 0, 0, 0);
}