use uncrustify to format linux kernel code
https://github.com/uncrustify/uncrustify
https://github.com/uncrustify/uncrustify/blob/master/etc/linux.cfg
#
# uncrustify config file for the linux kernel
#
indent_with_tabs = 2 # 1=indent to level only, 2=indent with tabs
input_tab_size = 8 # original tab size
output_tab_size = 8 # new tab size
indent_columns = output_tab_size
indent_label = 1 # pos: absolute col, neg: relative column
#
# inter-symbol newlines
#
nl_enum_brace = remove # "enum {" vs "enum \n {"
nl_union_brace = remove # "union {" vs "union \n {"
nl_struct_brace = remove # "struct {" vs "struct \n {"
nl_do_brace = remove # "do {" vs "do \n {"
nl_if_brace = remove # "if () {" vs "if () \n {"
nl_for_brace = remove # "for () {" vs "for () \n {"
nl_else_brace = remove # "else {" vs "else \n {"
nl_while_brace = remove # "while () {" vs "while () \n {"
nl_switch_brace = remove # "switch () {" vs "switch () \n {"
nl_brace_while = remove # "} while" vs "} \n while" - cuddle while
nl_brace_else = remove # "} else" vs "} \n else" - cuddle else
sp_brace_else = force
sp_else_brace = force
nl_func_var_def_blk = 1
nl_fcall_brace = remove # "list_for_each() {" vs "list_for_each()\n{"
nl_fdef_brace = add # "int foo() {" vs "int foo()\n{"
nl_after_label_colon = true # "fail:\nfree(foo);" vs "fail: free(foo);"
# nl_after_return = TRUE;
# nl_before_case = 1
#
# Source code modifications
#
mod_paren_on_return = remove # "return 1;" vs "return (1);"
#mod_full_brace_if = remove # "if (a) a--;" vs "if (a) { a--; }"
mod_full_brace_if_chain = true
mod_full_brace_for = remove # "for () a--;" vs "for () { a--; }"
mod_full_brace_do = remove # "do a--; while ();" vs "do { a--; } while ();"
mod_full_brace_while = remove # "while (a) a--;" vs "while (a) { a--; }"
mod_full_brace_nl = 3 # don't remove if more than 3 newlines
#
# inter-character spacing options
#
sp_return_paren = force # "return (1);" vs "return(1);"
sp_sizeof_paren = remove # "sizeof (int)" vs "sizeof(int)"
sp_before_sparen = force # "if (" vs "if("
sp_after_sparen = force # "if () {" vs "if (){"
sp_after_cast = remove # "(int) a" vs "(int)a"
sp_inside_braces = force # "{ 1 }" vs "{1}"
sp_inside_braces_struct = force # "{ 1 }" vs "{1}"
sp_inside_braces_enum = force # "{ 1 }" vs "{1}"
sp_assign = force
sp_arith = force
sp_bool = force
sp_compare = force
sp_assign = force
sp_after_comma = force
sp_func_def_paren = remove # "int foo (){" vs "int foo(){"
sp_func_call_paren = remove # "foo (" vs "foo("
sp_func_proto_paren = remove # "int foo ();" vs "int foo();"
#
# Aligning stuff
#
align_with_tabs = TRUE # use tabs to align
align_on_tabstop = TRUE # align on tabstops
# align_keep_tabs = true
align_enum_equ_span = 4 # '=' in enum definition
# align_nl_cont = TRUE
# align_var_def_span = 2
# align_var_def_inline = TRUE
# align_var_def_star = FALSE
# align_var_def_colon = TRUE
# align_assign_span = 1
align_struct_init_span = 3 # align stuff in a structure init '= { }'
align_right_cmt_span = 3
# align_pp_define_span = 8;
# align_pp_define_gap = 4;
cmt_star_cont = true
# indent_brace = 0
nl_func_paren = remove
nl_func_decl_start = remove
nl_func_decl_empty = remove
nl_func_decl_args = remove
nl_func_decl_end = remove
sp_inside_paren = remove
sp_inside_square = remove
sp_inside_paren_cast = remove
sp_inside_fparen = remove
sp_inside_sparen = remove
sp_paren_paren = remove
sp_before_ptr_star = force
sp_after_ptr_star = remove
sp_between_ptr_star = remove
align_func_params = true
align_var_struct_span = 6
eat_blanks_after_open_brace = true
eat_blanks_before_close_brace = true
pp_indent = remove
nl_start_of_file = remove
nl_end_of_file = force
nl_end_of_file_min = 1
nl_comment_func_def = 1