Dell Hotkeys (Type 178)

Source: the Dell WMI driver of Linux, dell-wmi-base.c, and the dumps of the data corpus.

Maps the scan codes of the hotkeys of a laptop to their functions, which the Dell WMI driver of Linux reads. Mappings run to the end of the structure, which carries no number of them of its own. Key code 0xFFFF is found for the keys of no known function, which the driver takes for an unknown key, while key code 0x00FF stands for a function of its own, the third programmable key. The structures of the data corpus refer to one string of spaces, which no field refers to.

Table 1. Dell Hotkeys structure
Offset	Version	Name	Length	Value	Description
`0x00`	2.0+	Type	`BYTE`	`178`	Dell Hotkeys indicator
`0x01`	2.0+	Length	`BYTE`	Varies	Length of the structure
`0x02`	2.0+	Handle	`WORD`	Varies
`0x04`	2.0+	Mappings	4 BYTEs each	Varies	Mappings, see below

Table 2. Mapping
Offset	Name	Length	Description
`0x00`	Scan Code	`WORD`	Scan code of the key, as the firmware reports it in the WMI events of the hotkeys
`0x02`	Key Code	`WORD`	Function of the key, as the Dell WMI driver numbers the functions