谁能向我解释一下它EV
的价值/proc/bus/input/devices
是什么?
键盘总是有价值的120013
。为什么?
答案1
它代表bitmask
设备支持的事件。
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
前面B
的代表bitmap
, N
, P
, S
, U
,H
只是相应名称值中的第一个字母,I
代表ID
。以有序的方式:
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.
位掩码
如您所知,计算机处理二进制,因此:
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101
...
因此,如果我有一个位图,5
其值可以保存位 0 和 2,换句话说,可以为每个数字命名并检查它们是否对应于某个值。
例如
A = 1, 001
B = 2, 010
C = 4, 100
然后,如果我有二进制MYVAR = 5
文件101
,则会检查:
MYVAR & A == TRUE (101 & 001 => 001)
MYVAR & B == FALSE (101 & 010 => 000)
MYVAR & C == TRUE (101 & 100 => 100 )
因此我的var有A和C。
内核使用更复杂的方式,并按偏移量设置位。原因之一是使用一台计算机 (CPU) 整数中可用的位数更多。例如查看KEY
位图。
所以,如果我们说:
A = 0
B = 1
C = 6
...
进而
target = 0;
set_bit(A, target); => target == 0001
set_bit(C, target); => target == 0100 0001
解码120013
该值为120013
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
从右数起,它们是:
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-event-codes.h
你发现它们对应于:
0 EV_SYN (0x00)
1 EV_KEY (0x01)
4 EV_MSC (0x04)
17 EV_LED (0x11)
20 EV_REP (0x14)
为了检查它们的含义,给出了快速介绍内核文档。
* 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,可能会引起兴趣。