Supplemental Material for Lecture 5: Char Devices

alloc_chrdev_region()

cdev_init(), cdev_alloc()

struct file
struct file_operations

fmode_t f_mode

set by kernel

unsigned int f_flags

combined flags and mode passed to open() system call

read/write/rdwr (flags, mode relationship)
do_sys_open()

Be aware that build_open_flags() returns 0 (success) or an error (not a file descriptor as the variable name seems to indicate)

read/write permission should be checked using f_mode rather than f_flags

container_of(ptr, type, member)