page256_or_1_byte_write

发布于 2020-02-14 21:02:50 浏览：1391 订阅该版

有个关于page256_or_1_byte_write 这个函数的问题
代码如下
```static sfud_err page256_or_1_byte_write(const sfud_flash *flash, uint32_t addr, size_t size, uint16_t write_gran,
        const uint8_t *data) {

sfud_err result = SFUD_SUCCESS;
    const sfud_spi *spi = &flash->spi;
    static uint8_t cmd_data[5 + SFUD_WRITE_MAX_PAGE_SIZE];
    uint8_t cmd_size;
    size_t data_size;

SFUD_ASSERT(flash);
    /* only support 1 or 256 */
    SFUD_ASSERT(write_gran == 1 || write_gran == 256);
    /* must be call this function after initialize OK */
    SFUD_ASSERT(flash->init_ok);
    /* check the flash address bound */
    if (addr + size > flash->chip.capacity) {
        SFUD_INFO("Error: Flash address is out of bound.");
        return SFUD_ERR_ADDR_OUT_OF_BOUND;
    }
    /* lock SPI */
    if (spi->lock) {
        spi->lock(spi);
    }

/* loop write operate. write unit is write granularity */
    while (size) {
        /* set the flash write enable */
        result = set_write_enabled(flash, true);
        if (result != SFUD_SUCCESS) {
            goto __exit;
        }
        cmd_data[0] = SFUD_CMD_PAGE_PROGRAM;
        make_adress_byte_array(flash, addr, &cmd_data[1]);
        cmd_size = flash->addr_in_4_byte ? 5 : 4;

/* make write align and calculate next write address */
        SFUD_INFO("addr=%d ",addr);
        if (addr % write_gran != 0) {
            if (size > write_gran - (addr % write_gran)) {
                data_size = write_gran - (addr % write_gran);
            } else {
                data_size = size;
            }
        } else {
            if (size > write_gran) {
                data_size = write_gran;
            }else {
                data_size = size;
            }
        }
        size -= data_size;
        addr += data_size;

memcpy(&cmd_data[cmd_size], data, data_size);
        result = spi->wr(spi, cmd_data, cmd_size + data_size, NULL, 0);
        if (result != SFUD_SUCCESS) {
            SFUD_INFO("Error: Flash write SPI communicate error.");
            goto __exit;
        }
        result = wait_busy(flash);
        if (result != SFUD_SUCCESS) {
            goto __exit;
        }
        data += data_size;
    }

__exit:
    /* set the flash write disable */
    set_write_enabled(flash, false);
    /* unlock SPI */
    if (spi->unlock) {
        spi->unlock(spi);
    }

return result;
}
```最终是调用result = spi->wr(spi, cmd_data, cmd_size + data_size, NULL, 0); 将数据写入flash
在执行之前可以看到data_size的值并不等于入参size,会根据page的大小和地址做改变，flash 每次写入应该写入一个page
那么若地址为page的起始地址，长度小于page，是不是应该先读取一个page的内容，然后在memcpy写入的数据，然后在写入page，
若地址不为page的起始地址，那么要考虑写入的长度是否在两个page内。
不知道我这样的理解对不对，但是这个函数并没有读取的操作。

还是说flash可以不以page进行写操作的么？