3 version of MKDEV: kernel, uapi, libc, why?

Wed, 11 Apr 2018 01:51:31 -0700 

Hi, Greg, Thomas

I find 3 version of MKDEV (actually 2 + makedev)

in include/linux/kdev_t.h

    #define MINORBITS               20
    #define MKDEV(ma,mi)            (((ma) << MINORBITS) | (mi))

in inlcude/uapi/linux/kdev_t.h

    #define MKDEV(ma,mi)            ((ma)<<8 | (mi))

in Android bionic

    #define makedev(__major, __minor) \
      ( \
        (((__major) & 0xfffff000ULL) << 32) | (((__major) & 0xfffULL) <<
    8) | \
        (((__minor) & 0xffffff00ULL) << 12) | (((__minor) & 0xffULL)) \
      )

if I use mknod("renderD128", S_IFCHR|0666, MKDEV(226, 128));
I get wrong device:
crw-rw-rw- 1 root graphics 0, 57984 2011-11-11 11:20 renderD128


if I use ("renderD128",S_IFCHR|0666, makedev(226, 128));
I get right device.

but, when I use: mknod("card0", S_IFCHR|0666, MKDEV(226, 0));
I can get right device.

BR.
Ning.

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