PS/2 Keyboard: Difference between revisions
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Modern keyboards should support all three scan code sets, however some don't. Scan code set 2 (the default) is the only scan code set that is guaranteed to be supported. In theory (I haven't tried it) it should be possible to attempt to set scan code set 1 or scan code set 3, and then ask the keyboard which scan code it is currently using and see if it actually is using the requested scan code set. In this way it may be possible to determine which scan code sets the keyboard does support.
Scan codes themselves are sequences of one or more bytes. In some cases the sequence can be as many as 6 bytes (e.g. the
generates the sequence 0xE1, 0x1D, 0x45, 0xE1, 0x9D, 0xC5 when pressed). This situation isn't really ideal. In general (for later processing) you want to convert these "one or more byte sequences" into a single integer that uniquely identifies a specific key, that can be used effectively in things like lookup tables (without having sparsely used "many GiB" lookup tables).
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Basically, when the keyboard driver's state machine knows it has received a complete scan code, the next step is to convert the "one or more byte" scan code into a key code.
=== Key Codes, Key States and Key Mappings ===
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