It represent the bitmask
for events supported by the device.
Sample of devices
entry for a AT Keyboard:
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
The B
in front stands for bitmap
, N
, P
, S
, U
, H
are simply first letter in corresponding name value and I
is for ID
. In ordered fashion:
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.
Bitmasks
As you know computers deal in binary, so:
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101
...
So if i have a bitmap with value 5
that one would hold bits 0 and 2 in other
word one can give each number a name and check if they correspond to a value.
E.g.
A = 1, 001
B = 2, 010
C = 4, 100
Then if I have MYVAR = 5
which is 101
in binary this would check out:
MYVAR & A == TRUE (101 & 001 => 001)
MYVAR & B == FALSE (101 & 010 => 000)
MYVAR & C == TRUE (101 & 100 => 100 )
Thus my var has A and C.
The kernel uses a bit more sophisticated/complex way, and set bits by
offset. One reason being that more bits then is available in one computer (CPU) integer is used. For example look at the KEY
bitmap.
So, if we say:
A = 0
B = 1
C = 6
...
And then
target = 0;
set_bit(A, target); => target == 0001
set_bit(C, target); => target == 0100 0001
Decoding 120013
The value 120013
is a hexadecimal. As binary it gives us:
0x120013 == 0001 0010 0000 0000 0001 0011 binary
1 2 0 0 1 3
Numbered from right they are:
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
Then check input-event-codes.h
you find that they correspond to:
0 EV_SYN (0x00)
1 EV_KEY (0x01)
4 EV_MSC (0x04)
17 EV_LED (0x11)
20 EV_REP (0x14)
To check what they mean a quick introduction is given by Kernel documentation.
* 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.
This, "EDIT 2 (continued):" in particular, might be of interest.
Best Answer
The first disk
/dev/sda
is8:0
(major:minor), but the major number 8 contains the next 15 disks too (Documentation/devices.txt
in the kernel source):The rest are for the rest of your drives (major numbers 66-71 and 128-134 are similar, and the partitioning scheme is the same for all of them):
Well, you probably don't have that many disks, and the system only generates the nodes that are required for the devices you actually have, so you don't see anything but
sda
and its partitions in/dev
.As for
vcsa
and friends, they're related to the virtual consoles:Also note that
/dev/vcs*
are character devices, not a block devices. The first letter in thels
output tells which one it is.