On 4/2/2022 7:03 AM, Xiang Xiao wrote:
Many functionality is accessed through ioctl callback, what permission is
needed before invoking ioctl?
By permissions, you mean open mode? Per POSIX, O_WRONLY, O_RDONLY, or
O_RDWR is required on any success open call (or O_EXEC or O_SEARCH).
But I did run across this non-standard Linux behavior in this man page:
https://man7.org/linux/man-pages/man2/open.2.html:
Under Linux, the*O_NONBLOCK *flag is sometimes used in cases where
one wants to open but does not necessarily have the intention to
read or write. For example, this may be used to open a device in
order to get a file descriptor for use withioctl(2)
<https://man7.org/linux/man-pages/man2/ioctl.2.html>.
