Linux kernel interface to external world is well defined (370+ system calls, man pages, etc.). However, is there any overview of internal kernel interfaces (between kernel subsystems, or device drivers)?
There is a section In–kernel APIs here, but it offers just scarce info.
This is a nice map of internal kernel organization:
But what about these kernel components interaction? And interaction between them and additional device drivers?
Your best bet would be the kernel documentation in the source. Download the source archive or checkout the git repository from https://www.kernel.org/. Then there are lots of files under the directory Documentation/ or use 'make htmldocs' for a html navigation. It is also hosted on several websites on the internet, such as https://www.kernel.org/doc/.
Some of interfaces found in the source code (kernel version 3.18.1): (source is almost verbatim from headers, except cosmetic changes; for inline fuctions and macros, I did't copy their body) (this is not complete answer - thi is means just to be a glimpse into huge number of kernel internal interface functions. I will add gradually some selected interfaces as I go through kernel)
(from file include/linux/spinlock.h)
static inline void spin_lock(spinlock_t *lock) static inline void spin_lock_bh(spinlock_t *lock) static inline int spin_trylock(spinlock_t *lock) static inline void spin_lock_irq(spinlock_t *lock) static inline void spin_unlock(spinlock_t *lock) static inline void spin_unlock_bh(spinlock_t *lock) static inline void spin_unlock_irq(spinlock_t *lock) static inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags) static inline int spin_trylock_bh(spinlock_t *lock) static inline int spin_trylock_irq(spinlock_t *lock) static inline void spin_unlock_wait(spinlock_t *lock) static inline int spin_is_locked(spinlock_t *lock) static inline int spin_is_contended(spinlock_t *lock) static inline int spin_can_lock(spinlock_t *lock) (from file include/linux/semaphore.h)
static inline void sema_init(struct semaphore *sem, int val); extern void down(struct semaphore *sem); extern int __must_check down_interruptible(struct semaphore *sem); extern int __must_check down_killable(struct semaphore *sem); extern int __must_check down_trylock(struct semaphore *sem); extern int __must_check down_timeout(struct semaphore *sem, long jiffies); extern void up(struct semaphore *sem); (from file include/linux/completion.h)
static inline void init_completion(struct completion *x) static inline void reinit_completion(struct completion *x) extern void wait_for_completion(struct completion *); extern void wait_for_completion_io(struct completion *); extern int wait_for_completion_interruptible(struct completion *x); extern int wait_for_completion_killable(struct completion *x); extern unsigned long wait_for_completion_timeout(struct completion *x, unsigned long timeout); extern unsigned long wait_for_completion_io_timeout(struct completion *x, unsigned long timeout); extern long wait_for_completion_interruptible_timeout(struct completion *x, unsigned long timeout); extern long wait_for_completion_killable_timeout(struct completion *x, unsigned long timeout); extern bool try_wait_for_completion(struct completion *x); extern bool completion_done(struct completion *x); extern void complete(struct completion *); extern void complete_all(struct completion *); (from file include/linux/hardirq.h)
extern void synchronize_irq(unsigned int irq); extern void synchronize_hardirq(unsigned int irq); extern void rcu_nmi_enter(void); extern void rcu_nmi_exit(void); #define __irq_enter() \ extern void irq_enter(void); #define __irq_exit() \ extern void irq_exit(void); #define nmi_enter() \ #define nmi_exit() \ (from file include/linux/interrupt.h)
extern irqreturn_t no_action(int cpl, void *dev_id); extern int __must_check request_threaded_irq(unsigned int irq, irq_handler_t handler, irq_handler_t thread_fn, unsigned long flags, const char *name, void *dev); static inline int __must_check request_irq(unsigned int irq, irq_handler_t handler, unsigned long flags, const char *name, void *dev) extern int __must_check request_any_context_irq(unsigned int irq, irq_handler_t handler, unsigned long flags, const char *name, void *dev_id); extern int __must_check request_percpu_irq(unsigned int irq, irq_handler_t handler, const char *devname, void __percpu *percpu_dev_id); extern void free_irq(unsigned int, void *); extern void free_percpu_irq(unsigned int, void __percpu *); extern int __must_check devm_request_threaded_irq(struct device *dev, unsigned int irq, irq_handler_t handler, irq_handler_t thread_fn, unsigned long irqflags, const char *devname, void *dev_id); static inline int __must_check devm_request_irq(struct device *dev, unsigned int irq, irq_handler_t handler, unsigned long irqflags, const char *devname, void *dev_id) extern int __must_check devm_request_any_context_irq(struct device *dev, unsigned int irq, irq_handler_t handler, unsigned long irqflags, const char *devname, void *dev_id); extern void devm_free_irq(struct device *dev, unsigned int irq, void *dev_id); # define local_irq_enable_in_hardirq() \ extern void disable_irq_nosync(unsigned int irq); extern void disable_irq(unsigned int irq); extern void disable_percpu_irq(unsigned int irq); extern void enable_irq(unsigned int irq); extern void enable_percpu_irq(unsigned int irq, unsigned int type); extern void irq_wake_thread(unsigned int irq, void *dev_id); extern void suspend_device_irqs(void); extern void resume_device_irqs(void); extern int __irq_set_affinity(unsigned int irq, const struct cpumask *cpumask, bool force); static inline int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask) static inline int irq_force_affinity(unsigned int irq, const struct cpumask *cpumask) extern int irq_can_set_affinity(unsigned int irq); extern int irq_select_affinity(unsigned int irq); extern int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m); extern int irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify); static inline void disable_irq_nosync_lockdep(unsigned int irq) static inline void disable_irq_nosync_lockdep_irqsave(unsigned int irq, unsigned long *flags) static inline void disable_irq_lockdep(unsigned int irq) static inline void enable_irq_lockdep(unsigned int irq) static inline void enable_irq_lockdep_irqrestore(unsigned int irq, unsigned long *flags) extern int irq_set_irq_wake(unsigned int irq, unsigned int on); static inline int enable_irq_wake(unsigned int irq) static inline int disable_irq_wake(unsigned int irq) #define set_softirq_pending(x) (local_softirq_pending() = (x)) #define or_softirq_pending(x) (local_softirq_pending() |= (x)) #define hard_irq_disable() do { } while(0) asmlinkage void do_softirq(void); asmlinkage void __do_softirq(void); void do_softirq_own_stack(void); extern void open_softirq(int nr, void (*action)(struct softirq_action *)); extern void softirq_init(void); extern void __raise_softirq_irqoff(unsigned int nr); extern void raise_softirq_irqoff(unsigned int nr); extern void raise_softirq(unsigned int nr); static inline struct task_struct *this_cpu_ksoftirqd(void) extern unsigned long probe_irq_on(void); /* returns 0 on failure */ extern int probe_irq_off(unsigned long); /* returns 0 or negative on failure */ extern unsigned int probe_irq_mask(unsigned long); /* returns mask of ISA interrupts */ extern void init_irq_proc(void); int show_interrupts(struct seq_file *p, void *v); int arch_show_interrupts(struct seq_file *p, int prec); extern int early_irq_init(void); extern int arch_probe_nr_irqs(void); extern int arch_early_irq_init(void); (from files include/asm-generic/bug.h or arch/<architecture>/include/asm/bug.h)
#define BUG() #define BUG_ON(<condition>) (from file arch/<architecture>/include/asm/uaccess.h)
#define MAKE_MM_SEG(s) ((mm_segment_t) { (s) }) #define KERNEL_DS MAKE_MM_SEG(-1UL) #define USER_DS MAKE_MM_SEG(TASK_SIZE_MAX) #define get_ds() (KERNEL_DS) #define get_fs() (current_thread_info()->addr_limit) #define set_fs(x) (current_thread_info()->addr_limit = (x)) #define segment_eq(a, b) ((a).seg == (b).seg) #define user_addr_max() (current_thread_info()->addr_limit.seg) #define __addr_ok(addr) \ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit) #define __range_not_ok(addr, size, limit) \ #define access_ok(type, addr, size) \ extern int fixup_exception(struct pt_regs *regs); extern int early_fixup_exception(unsigned long *ip); extern int __get_user_1(void); extern int __get_user_2(void); extern int __get_user_4(void); extern int __get_user_8(void); extern int __get_user_bad(void); #define __inttype(x) \ #define get_user(x, ptr) \ #define __put_user_x(size, x, ptr, __ret_pu) \ #define __put_user_asm_u64(x, addr, err, errret) \ #define __put_user_asm_ex_u64(x, addr) \ #define __put_user_x8(x, ptr, __ret_pu) \ #define __put_user_asm_u64(x, ptr, retval, errret) \ #define __put_user_asm_ex_u64(x, addr) \ #define __put_user_x8(x, ptr, __ret_pu) __put_user_x(8, x, ptr, __ret_pu) extern void __put_user_bad(void); extern void __put_user_1(void); extern void __put_user_2(void); extern void __put_user_4(void); extern void __put_user_8(void); #define put_user(x, ptr) \ #define __put_user_size(x, ptr, size, retval, errret) \ #define __put_user_size_ex(x, ptr, size) \ #define __get_user_asm_u64(x, ptr, retval, errret) (x) = __get_user_bad() #define __get_user_asm_ex_u64(x, ptr) (x) = __get_user_bad() #define __get_user_size(x, ptr, size, retval, errret) \ #define __get_user_asm(x, addr, err, itype, rtype, ltype, errret) \ #define __get_user_size_ex(x, ptr, size) \ #define __get_user_asm_ex(x, addr, itype, rtype, ltype) \ #define __put_user_nocheck(x, ptr, size) \ #define __get_user_nocheck(x, ptr, size) \ #define __put_user_asm(x, addr, err, itype, rtype, ltype, errret) \ #define __put_user_asm_ex(x, addr, itype, rtype, ltype) \ #define uaccess_try do { \ #define uaccess_catch(err) \ #define __get_user(x, ptr) \ #define __put_user(x, ptr) \ #define __get_user_unaligned __get_user #define __put_user_unaligned __put_user #define get_user_try uaccess_try #define get_user_catch(err) uaccess_catch(err) #define get_user_ex(x, ptr) do { \ #define put_user_try uaccess_try #define put_user_catch(err) uaccess_catch(err) #define put_user_ex(x, ptr) \ extern unsigned long copy_from_user_nmi(void *to, const void __user *from, unsigned long n); extern __must_check long strncpy_from_user(char *dst, const char __user *src, long count); extern __must_check long strlen_user(const char __user *str); extern __must_check long strnlen_user(const char __user *str, long n); unsigned long __must_check clear_user(void __user *mem, unsigned long len); unsigned long __must_check __clear_user(void __user *mem, unsigned long len); #define __user_atomic_cmpxchg_inatomic(uval, ptr, old, new, size) \ #define user_atomic_cmpxchg_inatomic(uval, ptr, old, new) \ unsigned long __must_check _copy_from_user(void *to, const void __user *from, unsigned n); unsigned long __must_check _copy_to_user(void __user *to, const void *from, unsigned n); static inline void __copy_from_user_overflow(int size, unsigned long count) static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n) static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)