On Thursday 21 April 2011, Michał Mirosław wrote:
> W dniu 21 kwietnia 2011 13:15 użytkownik Arnd Bergmann <[email protected]>
> napisał:
> static int mmc_blk_compat_ioctl(struct block_device *bdev, fmode_t mode,
> unsigned int cmd, unsigned long arg)
> {
> struct mmc_ioc_cmd blk;
>
> if (cmd != MMC_IOC_CMD)
> return -EINVAL;
>
> copy_from_user(compat_ptr(arg), &blk) ...
> blk.data_ptr = compat_ptr(blk.__data_ptr_storage32);
>
> return mmc_blk_ioctl_cmd(bdev, &blk);
> }
Yes, this works, but it requires having a compat_ioctl() handler function that
knows about the data structure, which we generally try to avoid.
The same method would even work if you only had a pointer member in the
structure and did not even attempt to make the structure compatible.
Arnd
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