Previously ioctl.c is a userspace program for chardev2.c and chardev.h [1].
But now, this file is an independent kernel module, and the original code
disappear.
This patch adds back the original userspace code and renames it to
userspace_ioctl.c.
[1] https://tldp.org/LDP/lkmpg/2.4/html/x856.html
Instead of using the old register_chrdev / unregister_chrdev API,
cdev interface which is newer and would be better for new driver programmers
in most cases. This commit is trying to give the brief overview for
this different interface.
This script do mainly 2 things:
1.
Generate file `Contributors` with git log in following format:
Contributor's name,<1-st e-mail>[,<2nd e-mail>][,<3rd e-mail>]...
The 2-nd email and so on are based on file `.mailmap` in the root
directory of the repo.
Note that it will also append contributors in File `Include`; and
will NOT append contributors in File `Exclude`.
If there are new contributors, script will sort `Contributor` after
append new contributors into each file; Otherwise it do nothing.
2.
Generate contrib.tex based on `Contributors` into lib/contrib.tex in
following format:
[name], (reasonable width) % [1-st e-mail]
Which is inspired by The Not So Short Introduction to Latex 2e[1]
We need to maintain `.mailmap`, `Exclude` and `Include` manually.
All Chinese name should be converted into English/Pinyin in `.mailmap`,
otherwise we may need extra pkg for latex to parse Chinese characters.
[1] - https://tobi.oetiker.ch/lshort/lshort.pdfClose#68
The dmesg command allows you to review the messages that are stored in the
ring buffer. Some Linux distributions have strict requirements for
dmesg, and you need to use sudo to use dmesg.
Since Linux v3.14, the read, write and seek operations of "struct file" are
guaranteed for thread safety [1][2]. This patch added an explanation.
Here are the potential problems:
chardev.c:
- Move the "msg_ptr" pointer into the read function to remove unnecessary usage.
- List the clear states of "already_open" by using mnemonic enumeration.
chardev2.c:
- The "buffer" in the write function is user space data. It cannot use in the
kernel space.
- Reduce the redundant type transformation.
- List the states of "already_open". Same as chardev.c.
[1] https://lore.kernel.org/lkml/20140303210359.26624.qmail@science.horizon.com/T/#u
[2] 9c225f2655
Parameters are case-sensitive, so myintArray is different from myintarray, and people who are running the example with copy/paste will find it doesn't work as described in the text.
In file {chardev,chardev2,sleep}.c, the variable to determine
the exclusive access was of integer type, which led to race
condition.
This patch rewrote the above with atomic CAS respectively
to eliminate the race.
Close#93
The term "reference count" would be better than "use count."
In addition, the usage of module_refcount(THIS_MODULE) was appended
for the reference counter query.
