LWN: Comments on "The cdev interface"

The cdev interface

netilovefm — Sun, 30 Aug 2015 08:49:38 +0000

now I have a question. I want to use this char_dev.

I see chrdev_open() function, in that function,

why in this function calls request_module() if not matching cdev and i_node->i_cdev

cdev is already added in system(usually module_init()function) then why call module again?

help me and answer plz T.T

The cdev interface

nosf — Fri, 11 Jun 2010 10:51:38 +0000

>* In order the device to actually apear in the file system, you have to >call device_create (class, parent_dev, devno, device_name).
>* In order to call device_create you need to have a device class object: >either use one of the existing classes, or create your own with create_class (THIS_MODULE, class_name)

I think this is for sysfs only.

The cdev interface

chandan_raka — Wed, 11 Nov 2009 11:17:35 +0000

Do I need to do mknod in order to add an entry into /dev?

Is there any way to create device in /dev without doing mknod from user space.
I tried to use device_create does didnt work.

The cdev interface

zap — Wed, 26 Nov 2008 13:27:02 +0000

This article seems a bit outdated, so I'll add my two cents here.

* cdev_add will return -errno as usually, returning 0 means success.
* In order the device to actually apear in the file system, you have to call device_create (class, parent_dev, devno, device_name).
* In order to call device_create you need to have a device class object: either use one of the existing classes, or create your own with create_class (THIS_MODULE, class_name).