Function ec_flash_write

src/security/vboot/ec_sync.c:242–317

* Send an image to the EC in burst-sized chunks. */

 * Send an image to the EC in burst-sized chunks.
 */
static vb2_error_t ec_flash_write(void *image, uint32_t region_offset,
				  int image_size)
{
	struct ec_response_get_protocol_info resp_proto;
	struct ec_response_flash_info resp_flash;
	ssize_t pdata_max_size;
	ssize_t burst;
	uint8_t *file_buf;
	struct ec_params_flash_write *params;
	uint32_t end, off;

	/*
	 * Get EC's protocol information, so that we can figure out how much
	 * data can be sent in one message.
	 */
	if (google_chromeec_get_protocol_info(&resp_proto)) {
		printk(BIOS_ERR, "Failed to get EC protocol information; "
		       "skipping flash write\n");
		return VB2_ERROR_UNKNOWN;
	}

	/*
	 * Determine burst size.  This must be a multiple of the write block
	 * size, and must also fit into the host parameter buffer.
	 */
	if (google_chromeec_flash_info(&resp_flash)) {
		printk(BIOS_ERR, "Failed to get EC flash information; "
		       "skipping flash write\n");
		return VB2_ERROR_UNKNOWN;
	}

	/* Limit the potential buffer stack allocation to 1K */
	pdata_max_size = MIN(1024, resp_proto.max_request_packet_size -
				   sizeof(struct ec_host_request));

	/* Round burst to a multiple of the flash write block size */
	burst = pdata_max_size - sizeof(*params);
	burst = (burst / resp_flash.write_block_size) *
		resp_flash.write_block_size;

	/* Buffer too small */
	if (burst <= 0) {
		printk(BIOS_ERR, "Flash write buffer too small!  skipping "
		       "flash write\n");
		return VB2_ERROR_UNKNOWN;
	}

	/* Allocate buffer on the stack */
	params = alloca(burst + sizeof(*params));

	/* Fill up the buffer */
	end = region_offset + image_size;
	file_buf = image;
	for (off = region_offset; off < end; off += burst) {
		uint32_t todo = MIN(end - off, burst);
		uint32_t xfer_size = todo + sizeof(*params);

		params->offset = off;