#ifndef _LINUX_KDEV_T_H
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#ifndef _LINUX_KDEV_T_H
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#define _LINUX_KDEV_T_H
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#define _LINUX_KDEV_T_H
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#ifdef __KERNEL__
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#ifdef __KERNEL__
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/*
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/*
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As a preparation for the introduction of larger device numbers,
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As a preparation for the introduction of larger device numbers,
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we introduce a type kdev_t to hold them. No information about
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we introduce a type kdev_t to hold them. No information about
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this type is known outside of this include file.
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this type is known outside of this include file.
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Objects of type kdev_t designate a device. Outside of the kernel
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Objects of type kdev_t designate a device. Outside of the kernel
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the corresponding things are objects of type dev_t - usually an
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the corresponding things are objects of type dev_t - usually an
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integral type with the device major and minor in the high and low
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integral type with the device major and minor in the high and low
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bits, respectively. Conversion is done by
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bits, respectively. Conversion is done by
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extern kdev_t to_kdev_t(int);
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extern kdev_t to_kdev_t(int);
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It is up to the various file systems to decide how objects of type
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It is up to the various file systems to decide how objects of type
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dev_t are stored on disk.
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dev_t are stored on disk.
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The only other point of contact between kernel and outside world
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The only other point of contact between kernel and outside world
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are the system calls stat and mknod, new versions of which will
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are the system calls stat and mknod, new versions of which will
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eventually have to be used in libc.
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eventually have to be used in libc.
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[Unfortunately, the floppy control ioctls fail to hide the internal
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[Unfortunately, the floppy control ioctls fail to hide the internal
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kernel structures, and the fd_device field of a struct floppy_drive_struct
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kernel structures, and the fd_device field of a struct floppy_drive_struct
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is user-visible. So, it remains a dev_t for the moment, with some ugly
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is user-visible. So, it remains a dev_t for the moment, with some ugly
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conversions in floppy.c.]
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conversions in floppy.c.]
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Inside the kernel, we aim for a kdev_t type that is a pointer
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Inside the kernel, we aim for a kdev_t type that is a pointer
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to a structure with information about the device (like major,
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to a structure with information about the device (like major,
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minor, size, blocksize, sectorsize, name, read-only flag,
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minor, size, blocksize, sectorsize, name, read-only flag,
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struct file_operations etc.).
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struct file_operations etc.).
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However, for the time being we let kdev_t be almost the same as dev_t:
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However, for the time being we let kdev_t be almost the same as dev_t:
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typedef struct { unsigned short major, minor; } kdev_t;
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typedef struct { unsigned short major, minor; } kdev_t;
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Admissible operations on an object of type kdev_t:
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Admissible operations on an object of type kdev_t:
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- passing it along
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- passing it along
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- comparing it for equality with another such object
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- comparing it for equality with another such object
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- storing it in ROOT_DEV, inode->i_dev, inode->i_rdev, sb->s_dev,
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- storing it in ROOT_DEV, inode->i_dev, inode->i_rdev, sb->s_dev,
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bh->b_dev, req->rq_dev, de->dc_dev, tty->device
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bh->b_dev, req->rq_dev, de->dc_dev, tty->device
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- using its bit pattern as argument in a hash function
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- using its bit pattern as argument in a hash function
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- finding its major and minor
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- finding its major and minor
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- complaining about it
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- complaining about it
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An object of type kdev_t is created only by the function MKDEV(),
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An object of type kdev_t is created only by the function MKDEV(),
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with the single exception of the constant 0 (no device).
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with the single exception of the constant 0 (no device).
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Right now the other information mentioned above is usually found
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Right now the other information mentioned above is usually found
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in static arrays indexed by major or major,minor.
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in static arrays indexed by major or major,minor.
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An obstacle to immediately using
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An obstacle to immediately using
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typedef struct { ... (* lots of information *) } *kdev_t
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typedef struct { ... (* lots of information *) } *kdev_t
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is the case of mknod used to create a block device that the
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is the case of mknod used to create a block device that the
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kernel doesn't know about at present (but first learns about
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kernel doesn't know about at present (but first learns about
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when some module is inserted).
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when some module is inserted).
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aeb - 950811
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aeb - 950811
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*/
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*/
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/* Since MINOR(dev) is used as index in static arrays,
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/* Since MINOR(dev) is used as index in static arrays,
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the kernel is not quite ready yet for larger minors.
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the kernel is not quite ready yet for larger minors.
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However, everything runs fine with an arbitrary kdev_t type. */
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However, everything runs fine with an arbitrary kdev_t type. */
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#define MINORBITS 8
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#define MINORBITS 8
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#define MINORMASK ((1<<MINORBITS) - 1)
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#define MINORMASK ((1<<MINORBITS) - 1)
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/* SIMON I won't fuck with this one */
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/* SIMON I won't fuck with this one */
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/*typedef unsigned short kdev_t;*/
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/*typedef unsigned short kdev_t;*/
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typedef int kdev_t;
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typedef int kdev_t;
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#define MAJOR(dev) ((dev) >> MINORBITS)
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#define MAJOR(dev) ((dev) >> MINORBITS)
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#define MINOR(dev) ((dev) & MINORMASK)
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#define MINOR(dev) ((dev) & MINORMASK)
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#define HASHDEV(dev) (dev)
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#define HASHDEV(dev) (dev)
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#define NODEV 0
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#define NODEV 0
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#define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))
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#define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))
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#define B_FREE 0xffff /* yuk */
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#define B_FREE 0xffff /* yuk */
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extern char * kdevname(kdev_t); /* note: returns pointer to static data! */
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extern char * kdevname(kdev_t); /* note: returns pointer to static data! */
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/*
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/*
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As long as device numbers in the outside world have 16 bits only,
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As long as device numbers in the outside world have 16 bits only,
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we use these conversions.
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we use these conversions.
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*/
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*/
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static inline unsigned int kdev_t_to_nr(kdev_t dev) {
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static inline unsigned int kdev_t_to_nr(kdev_t dev) {
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return (MAJOR(dev)<<8) | MINOR(dev);
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return (MAJOR(dev)<<8) | MINOR(dev);
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}
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}
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static inline kdev_t to_kdev_t(int dev)
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static inline kdev_t to_kdev_t(int dev)
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{
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{
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int major, minor;
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int major, minor;
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#if 0
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#if 0
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major = (dev >> 16);
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major = (dev >> 16);
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if (!major) {
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if (!major) {
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major = (dev >> 8);
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major = (dev >> 8);
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minor = (dev & 0xff);
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minor = (dev & 0xff);
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} else
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} else
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minor = (dev & 0xffff);
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minor = (dev & 0xffff);
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#else
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#else
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major = (dev >> 8);
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major = (dev >> 8);
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minor = (dev & 0xff);
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minor = (dev & 0xff);
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#endif
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#endif
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return MKDEV(major, minor);
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return MKDEV(major, minor);
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}
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}
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#else /* __KERNEL__ */
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#else /* __KERNEL__ */
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/*
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/*
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Some programs want their definitions of MAJOR and MINOR and MKDEV
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Some programs want their definitions of MAJOR and MINOR and MKDEV
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from the kernel sources. These must be the externally visible ones.
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from the kernel sources. These must be the externally visible ones.
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*/
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*/
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#define MAJOR(dev) ((dev)>>8)
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#define MAJOR(dev) ((dev)>>8)
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#define MINOR(dev) ((dev) & 0xff)
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#define MINOR(dev) ((dev) & 0xff)
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#define MKDEV(ma,mi) ((ma)<<8 | (mi))
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#define MKDEV(ma,mi) ((ma)<<8 | (mi))
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#endif /* __KERNEL__ */
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#endif /* __KERNEL__ */
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#endif
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#endif
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