If a have a /开发者_如何学编程dev device node and its major/minor numbers how do i know the kernel module name that exported this node?
Short answer :
cd /sys/dev/char/major:minor/device/driver/
ls -al | grep module
Each device is generally associated with a driver, and this is all what the "device model" is about. The sysfs
filesystem contains a representation of this devices and their associated driver. Unfortuantely, it seems not all sysfs have a representation of the device nodes, so this applyd only if your /sys directory contains a /dev directory.
Let's take an example, with /dev/video0
On my board, ls -al /dev/video0
output is
crw------- 1 root root 81, 0 Jan 1 00:00 video0
So major number is 81 and minor number is 0. Let's dive into sysfs :
# cd /sys
# ls
block class devices fs module
bus dev firmware kernel
The sys/dev
directory contains entry for the char and block devices of the system :
# cd dev
# cd char
# ls
10:61 13:64 1:3 1:8 249:0 252:0 29:0 4:65 81:0 89:1
10:62 1:1 1:5 1:9 250:0 253:0 29:1 5:0 81:2
10:63 1:11 1:7 248:0 251:0 254:0 4:64 5:1 81:3
What the hell are this links with strange names ? Remember the major and minor number, 81 and 0 ? Let's follow this link :
#cd major:minor (ie 81:0)
#ls -al
drwxr-xr-x 2 root root 0 Jan 1 01:56 .
drwxr-xr-x 3 root root 0 Jan 1 01:56 ..
-r--r--r-- 1 root root 4096 Jan 1 01:56 dev
lrwxrwxrwx 1 root root 0 Jan 1 01:56 device -> ../../../vpfe-capture
-r--r--r-- 1 root root 4096 Jan 1 01:56 index
-r--r--r-- 1 root root 4096 Jan 1 01:56 name
lrwxrwxrwx 1 root root 0 Jan 1 01:56 subsystem -> ../../../../../class/video4linux
-rw-r--r-- 1 root root 4096 Jan 1 01:56 uevent
Now we can see that this device nod, which is how the device is presented to userspace, is associated with a kernel device. This association is made through a link. If we follow this link, we end up in a directory, with a driver link. The name of the driver is usually the name of the module :
# ls -al
drwxr-xr-x 3 root root 0 Jan 1 01:56 .
drwxr-xr-x 25 root root 0 Jan 1 00:00 ..
lrwxrwxrwx 1 root root 0 Jan 1 01:56 driver -> ../../../bus/platform/drivers/vpfe-capture
-r--r--r-- 1 root root 4096 Jan 1 01:56 modalias
lrwxrwxrwx 1 root root 0 Jan 1 01:56 subsystem -> ../../../bus/platform
-rw-r--r-- 1 root root 4096 Jan 1 01:56 uevent
drwxr-xr-x 3 root root 0 Jan 1 01:56 video4linux
So here the name of the module is vpfe_capture
The answer to this question is most likely different based on a number of factors. For example, if you're running udev, devfs, pre-devfs, etc.
If you're using Ubuntu (or another equally modern distro) the udevadm
command might be what you want.
% udevadm info -q path -n /dev/cdrom
/devices/pci0000:00/0000:00:1f.1/host3/target3:0:0/3:0:0:0/block/sr0
So, my /dev/cdrom is provided by the sr
driver, which resides in the sr_mod
kernel module. I don't know of a command that takes /dev/cdrom
as an argument and prints sr_mod
as output.
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