CHAPTER 2

Device Drivers

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General Conversion Steps

Check and Extend Use of Derived Types

System-derived types, such as size_t, should be used where possible so that the resulting variables make sense when passed between functions. The new derived types uintptr_t or intptr_t should be used as the integral type for pointers.

Fixed-width integer types are useful for representing explicit sizes of binary data structures or hardware registers, while fundamental C language data types, such as int, can still be used for loop counters or file descriptors.

Some system-derived types represent 32-bit quantities on a 32-bit system but represent 64-bit quantities on a 64-bit system. Derived types that change size in this way include: clock_t, daddr_t, dev_t, ino_t, intptr_t, off_t, size_t, ssize_t, time_t, and uintptr_t.

Drivers that use these derived types should pay particular attention to their use, particularly if they are assigning these values to variables of another derived type, such as a fixed-width type.

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