技術標籤：#uboot原始碼分析核心驅動#ubuntu

/**
 * nand_write_skip_bad:
 *
 * Write image to NAND flash.
 * Blocks that are marked bad are skipped and the is written to the next
 * block instead as long as the image is short enough to fit even after
 * skipping the bad blocks.  Due to bad blocks we may not be able to
 * perform the requested write.  In the case where the write would
 * extend beyond the end of the NAND device, both length and actual (if
 * not NULL) are set to 0.  In the case where the write would extend
 * beyond the limit we are passed, length is set to 0 and actual is set
 * to the required length.
 *
 * @param nand  	NAND device
 * @param offset	offset in flash
 * @param length	buffer length
 * @param actual	set to size required to write length worth of
 *			buffer or 0 on error, if not NULL
 * @param lim		maximum size that actual may be in order to not
 *			exceed the buffer
 * @param buffer        buffer to read from
 * @param flags		flags modifying the behaviour of the write to NAND
 * @return		0 in case of success
 */
 

int nand_write_skip_bad(nand_info_t *nand, loff_t offset, size_t *length,
		size_t *actual, loff_t lim, u_char *buffer, int flags)
{
	int rval = 0, blocksize;
	size_t left_to_write = *length;
	size_t used_for_write = 0;
	u_char *p_buffer = buffer;
	int need_skip;

	if (actual)
		*actual = 0;

	blocksize =
 
 nand->erasesize;

	/*
	 * nand_write() handles unaligned, partial page writes.
	 *
	 * We allow length to be unaligned, for convenience in
	 * using the $filesize variable.
	 *
	 * However, starting at an unaligned offset makes the
	 * semantics of bad block skipping ambiguous (really,
	 * you should only start a block skipping access at a
	 * partition boundary).  So don't try to handle that.
	 */
 

	if ((offset & (nand->writesize - 1)) != 0) {	//-- 頁不對齊，出錯誤返回
		printf("Attempt to write non page-aligned data\n");
		*length = 0;
		return -EINVAL;
	}

	need_skip = check_skip_len(nand, offset, *length, &used_for_write);//-- 計算含壞塊後的寫總長度，用used_for_write返回

	if (actual)
		*actual = used_for_write;

	if (need_skip < 0) {//-- 說明要寫的區域超過的裝置容量
		printf("Attempt to write outside the flash area\n");
		*length = 0;
		return -EINVAL;
	}

	if (used_for_write > lim) {
		puts("Size of write exceeds partition or device limit\n");
		*length = 0;
		return -EFBIG;
	}

	if (!need_skip && !(flags & WITH_DROP_FFS)) {//-- 沒有壞塊並且flag不是WITH_DROP_FFS引數,直接按length長度寫入
		rval = nand_write(nand, offset, length, buffer);

		if ((flags & WITH_WR_VERIFY) && !rval)
			rval = nand_verify(nand, offset, *length, buffer);

		if (rval == 0)
			return 0;

		*length = 0;
		printf("NAND write to offset %llx failed %d\n",
			offset, rval);
		return rval;
	}

	while (left_to_write > 0) {
		size_t block_offset = offset & (nand->erasesize - 1);	//-- 獲取塊內偏移,例如一個page 2048個位元組，對於第2個page來說，在該塊內該值為4096
		size_t write_size, truncated_write_size;

		WATCHDOG_RESET();

		//-- offset & ~(nand->erasesize - 1)算出來的值是要寫入的page所在的block的第一個page的第一個位元組。比如一個block有64個page，一個page有2048個位元組，如果要
		//-- 要寫第10個block的第2個page，那麼該值為10 * 64 * 2048.此處應該就是壞塊標記，是按照該塊的第一個page的第一個位元組是否為0xff來判斷是否為壞塊。
		if (nand_block_isbad(nand, offset & ~(nand->erasesize - 1))) {//-- 跳過一個壞塊
			printf("Skip bad block 0x%08llx\n",
				offset & ~(nand->erasesize - 1));
			offset += nand->erasesize - block_offset;
			continue;
		}

		if (left_to_write < (blocksize - block_offset))
			write_size = left_to_write;
		else
			write_size = blocksize - block_offset;

		truncated_write_size = write_size;
#ifdef CONFIG_CMD_NAND_TRIMFFS
		if (flags & WITH_DROP_FFS)
			truncated_write_size = drop_ffs(nand, p_buffer,
					&write_size);
#endif

		rval = nand_write(nand, offset, &truncated_write_size,
				p_buffer);

		if ((flags & WITH_WR_VERIFY) && !rval)
			rval = nand_verify(nand, offset,//-- 將寫入的資料再讀一遍驗證寫入是否正確
				truncated_write_size, p_buffer);

		offset += write_size;
		p_buffer += write_size;

		if (rval != 0) {
			printf("NAND write to offset %llx failed %d\n",
				offset, rval);
			*length -= left_to_write;
			return rval;
		}

		left_to_write -= write_size;
	}

	return 0;
}