Answers:
它代表bitmask
设备支持的for事件。
devices
AT键盘输入示例:
I: Bus=0011 Vendor=0001 Product=0001 Version=ab41
N: Name="AT Translated Set 2 keyboard"
P: Phys=isa0060/serio0/input0
S: Sysfs=/devices/platform/i8042/serio0/input/input2
U: Uniq=
H: Handlers=sysrq kbd event2
B: PROP=0
B: EV=120013
B: KEY=20000 200 20 0 0 0 0 500f 2100002 3803078 f900d401 feffffdf ffefffff ffffffff fffffffe
B: MSC=10
B: LED=7
在B
前面的代表bitmap
,N
,P
,S
,U
,H
在相应的名字值只是第一个字母,I
是ID
。以有序方式:
I => @id: id of the device
(struct input_id)
Bus => id.bustype
Vendor => id.vendor
Product => id.product
Version => id.version
N => name of the device.
P => physical path to the device in the system hierarchy.
S => sysfs path.
U => unique identification code for the device (if device has it).
H => list of input handles associated with the device.
B => bitmaps
PROP => device properties and quirks.
EV => types of events supported by the device.
KEY => keys/buttons this device has.
MSC => miscellaneous events supported by the device.
LED => leds present on the device.
如您所知,计算机以二进制形式处理,因此:
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101
...
因此,如果我有一个位图,其值5
可以容纳换句话说的0和2位,则可以给每个数字起一个名称,并检查它们是否对应于一个值。
例如
A = 1, 001
B = 2, 010
C = 4, 100
那么,如果我MYVAR = 5
是101
二进制,这将检查:
MYVAR & A == TRUE (101 & 001 => 001)
MYVAR & B == FALSE (101 & 010 => 000)
MYVAR & C == TRUE (101 & 100 => 100 )
因此我的变量有 A和C。
内核使用更复杂的方式,并通过偏移量设置位。原因之一是使用了一台计算机(CPU)整数中的更多位数。例如看KEY
位图。
因此,如果我们说:
A = 0
B = 1
C = 6
...
接着
target = 0;
set_bit(A, target); => target == 0001
set_bit(C, target); => target == 0100 0001
120013
取值120013
为十六进制。作为二进制,它给我们:
0x120013 == 0001 0010 0000 0000 0001 0011 binary
1 2 0 0 1 3
从右到右编号为:
2 1 <= offset (10's)
3210 9876 5432 1098 7654 3210 <= offset (counted from right)
0001 0010 0000 0000 0001 0011 <= binary
Set bits are:
0, 1, 4, 17, 20
然后检查input.h
您是否发现它们对应于:
0 EV_SYN (0x00)
1 EV_KEY (0x01)
4 EV_MSC (0x04)
17 EV_LED (0x11)
20 EV_REP (0x14)
要检查它们的含义,内核文档提供了快速介绍。
* EV_SYN:
- Used as markers to separate events. Events may be separated in time or in
space, such as with the multitouch protocol.
* EV_KEY:
- Used to describe state changes of keyboards, buttons, or other key-like
devices.
* EV_MSC:
- Used to describe miscellaneous input data that do not fit into other types.
* EV_LED:
- Used to turn LEDs on devices on and off.
* EV_REP:
- Used for autorepeating devices.
这,“编辑2(续):”特别是,可能会感兴趣。
0x120013
,但至少会如此。您不想做if(ev == 0x120013){ isKeyboard = true; }
,您想做if((ev & 0x120013) == 0x120013){ isKeyboard = true; }