Data Type used in kernel .

[Nicholas Mc Guire]

On Fri, Dec 23, 2016 at 06:33:28AM -0500, Pasquier, Thomas wrote:
> Hello Wasim,
> 
> On Fri, Dec 23, 2016 at 6:20 AM, Wasim Akram <wasim7702843288 at gmail.com>
> wrote:
> 
> > Hi ,
> >
> > I have seen "bool" data type  is used in linux kernel code . Can we
> > get documentation on data type used in linux kernel development ?
> >
> 
> I think this should be a good start:
> http://lxr.free-electrons.com/source/include/linux/types.h
>
one of the problems though is that there are a number of
"historic" type systems "left over" in the kernel it seems so
there actually is a bit of a mess and its not simple to 
figure out what things really are. For x86_64 I have a list
of type matches I use for code reading (still not complete)
which might help.
 
x86 64bit:
==========

Type              : equivalent types
bool              : _Bool,
char              : signed char, __signed__ char, __s8, s8, int8_t
unsigned char     : unsigned char, u_char, __u8, u8, unchar, u_int8_t, uint8_t
                    __ticket_t,
                    insn_byte_t,
                    kprobe_opcode_t
short             : signed short, __signed__ short, s16, int16_t
unsigned short    : unsigned short, __u16, u16, u_short, ushort, u_int16_t, uint16_t,
                    __sum16,
                    umode_t,
                    __ticketpair_t,
                    apm_eventinfo_t,
                    apm_event_t,
                    Elf32_Sword,
                    Elf32_Half,
                    Elf64_Half,
                    Elf64_SHalf,
                    __kernel_sa_family_t,
                    __kernel_gid16_t, gid16_t,
                    __kernel_uid16_t, uid16_t,
                    __kernel_old_uid_t, old_uid_t,
                    __kernel_old_gid_t, old_gid_t,
                    arch cond: __le16/__be16
int               : signed int, __signed__ int, __s32, s32, int32_t,  s_int32_t      
                    Elf64_Sword,
                    Elf64_Sxword,
                    key_serial_t,
                    insn_value_t,
                    __kernel_daddr_t, daddr_t,
                    __kernel_ipc_pid_t, pid_t,
                    __kernel_pid_t,
                    __kernel_mqd_t, mqd_t,
                    __kernel_key_t, key_t,
                    __kernel_timer_t timer_t,
unsigned int      : unsigned, unsigned int, __u32, u32, u_int32_t, uInt, u_int, uint, uint32_t,
                    __wsum,
                    nlink_t,
                    gfp_t,
                    fmode_t,
                    oom_flags_t,
                    isolate_mode_t,
                    Elf32_Addr,
                    Elf32_Off,
                    Elf32_Word,
                    Elf64_Word,
                    key_perm_t,
                    insn_attr_t,
                    sk_buff_data_t,
                    sctp_assoc_t.
                    __kernel_dev_t, dev_t, 
                    __kernel_uid32_t, uid_t, projid_t, qid_t
                    __kernel_gid32_t, gid_t,
                    __kernel_uid_t, 
                    __kernel_gid_t,
                    __kernel_mode_t, mode_t,
                    arch cond: __le32/__be32
long              : signed long, __kernel_long_t, 
                    __kernel_suseconds_t, suseconds_t,
                    __kernel_ssize_t, ssize_t,
                    __kernel_ptrdiff_t,
                    __kernel_off_t, off_t,
                    __kernel_time_t, time_t,
                    __kernel_clock_t, clock_t,
unsigned long     : __kernel_ulong_t, u_long, ulong
                    uintptr_t,
                    sector_t,
                    blkcnt_t,
                    irq_hw_number_t,
                    pteval_t,
                    pmdval_t,
                    pudval_t,
                    pgdval_t,
                    pgprotval_t,
                    vm_flags_t,
                    elf_greg_t,
                    cputime_t,
                    old_sigset_t,
                    aio_context_t,
                    flow_compare_t,
                    __kernel_ino_t, ino_t 
                    __kernel_old_dev_t
                    __kernel_size_t. size_t,
                    arch cond: __le64/__be64
long long         : signed long long, __signed__ long long, __s64, s64, int64_t
                    time64_t,
                    qsize_t,
                    __kernel_loff_t, loff_t,
unsigned long long: u64, __u64, uint64_t, u_int64_t
                    dma_addr_t,
                    cycles_t,
                    phys_addr_t, resource_size_t
                    cycle_t,
                    Elf64_Addr,
                    Elf64_Off,
                    Elf64_Xword,
                    cputime64_t,
                    netdev_features_t