(probably a question with a very simple answer, i just don't know what it is.) i'm currently trying to document the use of the "misc" char driver to quickly and conveniently create a character driver. there's a decent explanation of misc drivers in the book "essential linux device drivers", as well as a nice example here: http://virtlog.com/2008/03/25/linux-miscdevice-sample/ but here's where i get confused. what a misc char driver does is combine a lot of what you'd normally do in creating a regular char driver in a single call. on page 160 of ELDD, it's explained that a single call to misc_register() does all of the following that you would normally have to do yourself for a regular char driver: * allocates major/minor number via alloc_chrdev_region() * creates /dev and /sys nodes via call to class_device_create() * registers itself as a char driver using cdev_init() and cdev_add() sure enough, i compiled that sample misc char driver (called "mymisc"), loaded it and got an entry for that module both under /sys and under /dev, where i now have the device file: crw------- 1 root root 10, 56 2011-04-23 08:18 /dev/mymisc but here's the confusing part. who or what created that /dev entry? i always thought that was the job of udev, but i never added any udev rule for this new driver. so how did that new /dev file come to be? is there some sort of generic udev rule that would have handled this? also, the ELDD book claims that misc_register() calls the kernel routine class_device_create(). i'm looking at the entire kernel implementation for misc drivers in drivers/char/misc.c, and what i see is a call to device_create() instead. i suspect i should start following the flow of control here, but i'm still curious as to how that /dev file came into existence without any obvious help from udev. rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ======================================================================== _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
