Writing Device Drivers

x86 Processor Issues

Data types have no alignment restrictions. However, extra memory cycles might be required for the x86 processor to properly handle misaligned data transfers.

Note –

Drivers should not perform floating-point operations, as these operations are not supported in the kernel.

x86 Byte Ordering

The x86 processors use little-endian byte ordering. The least significant byte (LSB) of an integer is stored at the lowest address of the integer. The most significant byte is stored at the highest address for data items in this processor. For example, byte 7 is the most significant byte for 64-bit processors.

Diagram shows how bytes are ordered in little-endian architectures, that is, byte 0 is the least significant byte.

x86 Architecture Manuals

Both Intel Corporation and AMD publish a number of books on the x86 family of processors. See http://www.intel.com and http://www.amd.com.