问如何正确地将mtdblock读写到linux内核空间？
EN

Stack Overflow用户

提问于 2016-06-02 04:08:43

回答 1查看 1.1K关注 0票数 0

我有密码：

static unsigned char buffer[512];
static struct mtd_info *mtd_ptr = NULL;
static unsigned int *counter = NULL;

static void mtdblock_read(void)
{
  int readed = 0;
  int ret = 0;
  const unsigned int mtd_device_num = 12;
  counter = (unsigned int *)buffer;
  mtd_ptr = get_mtd_device(NULL, mtd_device_num);
  if(IS_ERR(mtd_ptr)){
    printk("Can't get mtd partition...");
    mtd_ptr = NULL;
    return;
  }
  printk("Found partition '%s'\n", mtd_ptr->name);
  if(mtd_ptr->read)
  {
    ret = mtd_ptr->read(mtd_ptr, 0, sizeof(buffer), &readed, buffer);
    printk("%s:%d - %d, readed: %d\n", __func__, __LINE__, ret, readed);
  }
  else
    printk("Not have 'read' ops\n");
  printk("current counter = 0x%08X\n", *counter);
}

static void mtdblock_write(void)
{
  int writed = 0;
  int ret = 0;
  (*counter) = 111;
  printk("Write counter (%d) to mtd\n", *counter);
  if(mtd_ptr && mtd_ptr->write)
  {
    ret = mtd_ptr->write(mtd_ptr, 0, sizeof(buffer), &writed, buffer);
    printk("%s:%d - %d, writed: %d\n", __func__, __LINE__, ret, writed);
    if(mtd_ptr->sync)
      mtd_ptr->sync(mtd_ptr);
  }
  else
    printk("Not have 'write' ops or mtd is not available\n");
}

void test()
{
  mtdblock_read();
  mtdblock_write();
  mtdblock_read();
}

mtdblock_read必须从and块读取512个字节，并将int值显示到缓冲区的前4个字节中。

mtdblock_write将4字节值放在512字节缓冲区的开头，并将其写入and块.

test()执行测试序列：

1 mtdblock_read() -从1st块读取当前值。
mtdblock_write() -用于写入新值
2 mtdblock_read() -用于重读writed值。

mtdblock_read中有问题(作为我的意见)，因为我有跟踪输出：

Found 13 partition 'dying_gasp'
mtdblock_read:303 - 0, readed: 512
current counter = 0x00000000
Write counter (1953719668) to mtd
mtdblock_write:322 - 0, writed: 512
Found 13 partition 'dying_gasp'
mtdblock_read:303 - 0, readed: 512
current counter = 0x00000000

从这里我可以看到mtd_ptr->read()有返回值-74，但是报告给readed，它有512字节从mtdblock读取。但实际上，它不是从mtdblock读取数据。此外，我检查了mtd_ptr-> writed ()，但是它正确地报告了512字节，并且返回值为零。

你能帮我解决这个问题吗？这是内部mtdblock驱动程序错误，还是我在读或写mtdlock时跳过主要操作？

linux-kernel

embedded

回答 1

Stack Overflow用户

回答已采纳

发布于 2021-08-03 09:53:13

对于提出问题的人来说，这有点晚了，但也许其他人可以从中受益。

如果mtd设备由SPI驱动程序支持，则无法读取声明为静态的缓冲区。spi.c中的spi_map_buf()中有一部分代码检查这一点：

if (vmalloced_buf || kmap_buf) {
        desc_len = min_t(int, max_seg_size, PAGE_SIZE);
        sgs = DIV_ROUND_UP(len + offset_in_page(buf), desc_len);
    } else if (virt_addr_valid(buf)) {
        desc_len = min_t(int, max_seg_size, ctlr->max_dma_len);
        sgs = DIV_ROUND_UP(len, desc_len);
    } else {
        dev_err(&ctlr->dev,"Not vmalloced, not kmap, va not valid\n");
        return -EINVAL;
    }