doc: Add initial documentation for coding style

1 files changed, 268 insertions, 0 deletions

diff --git a/doc/coding-style.txt b/doc/coding-style.txt
new file mode 100644
index 000000000..2ec98ee6e
--- /dev/null
+++ b/doc/coding-style.txt
@@ -0,0 +1,268 @@
+BlueZ coding style
+******************
+
+Every project has its coding style, and BlueZ is not an exception. This
+document describes the preferred coding style for BlueZ code, in order to keep
+some level of consistency among developers so that code can be easily
+understood and maintained.
+
+First of all, BlueZ coding style must follow every rule for Linux kernel
+(http://www.kernel.org/doc/Documentation/CodingStyle). There also exists a tool
+named checkpatch.pl to help you check the compliance with it. Just type
+"checkpatch.pl --no-tree patch_name" to check your patch. In theory, you need
+to clean up all the warnings and errors except this one: "ERROR: Missing
+Signed-off-by: line(s)". BlueZ does not used Signed-Off lines, so including
+them is actually an error.  In certain circumstances one can ignore the 80
+character per line limit.  This is generally only allowed if the alternative
+would make the code even less readable.
+
+Besides the kernel coding style above, BlueZ has special flavors for its own.
+Some of them are mandatory (marked as 'M'), while some others are optional
+(marked as 'O'), but generally preferred.
+
+M1: Blank line before and after an if/while/do/for statement
+============================================================
+
+There should be a blank line before if statement unless the if is nested and
+not preceded by an expression or variable declaration.
+
+Example:
+1)
+a = 1;
+if (b) {  // wrong
+
+2)
+a = 1
+
+if (b) {
+}
+a = 2;	// wrong
+
+3)
+if (a) {
+	if (b)  // correct
+
+4)
+b = 2;
+
+if (a) {	// correct
+
+}
+
+b = 3;
+
+The only exception to this rule applies when a variable is being checked for
+errors as such:
+
+err = stat(filename, &st);
+if (err || !S_ISDIR(st.st_mode))
+	return;
+
+M2: Multiple line comment
+=========================
+
+If your comments have more then one line, please start it from the second line.
+
+Example:
+/*
+ * first line comment	// correct
+ * ...
+ * last line comment
+ */
+
+
+M3: Space before and after operator
+===================================
+
+There should be a space before and after each operator.
+
+Example:
+a + b;  // correct
+
+
+M4: Wrap long lines
+===================
+
+If your condition in if, while, for statement or a function declaration is too
+long to fit in one line, the new line needs to be indented not aligned with the
+body.
+
+Example:
+1)
+if ((adapter->supported_settings & MGMT_SETTING_SSP) &&
+	!(adapter->current_settings & MGMT_SETTING_SSP)) // wrong
+
+2)
+if ((adapter->supported_settings & MGMT_SETTING_SSP) &&
+				!(adapter->current_settings & MGMT_SETTING_SSP))
+
+3)
+void btd_adapter_register_pin_cb(struct btd_adapter *adapter,
+				 btd_adapter_pin_cb_t cb) // wrong
+
+4)
+void btd_adapter_register_pin_cb(struct btd_adapter *adapter,
+							btd_adapter_pin_cb_t cb)
+
+The referred style for line wrapping is to indent as far as possible to the
+right without hitting the 80 columns limit.
+
+M5: Space when doing type casting
+=================================
+
+There should be a space between new type and variable.
+
+Example:
+1)
+a = (int *)b;  // wrong
+2)
+a = (int *) b;  // correct
+
+
+M6: Don't initialize variable unnecessarily
+===========================================
+
+When declaring a variable, try not to initialize it unless necessary.
+
+Example:
+int i = 1;  // wrong
+
+for (i = 0; i < 3; i++) {
+}
+
+M7: Follow the order of include header elements
+===============================================
+
+When writing an include header the various elements should be in the following
+order:
+	- #includes
+	- forward declarations
+	- #defines
+	- enums
+	- typedefs
+	- function declarations and inline function definitions
+
+M8: Internal headers must not use include guards
+================================================
+
+Any time when creating a new header file with non-public API, that header
+must not contain include guards.
+
+M9: Naming of enums
+===================
+
+Enums must have a descriptive name.  The enum type should be small caps and
+it should not be typedef-ed.  Enum contents should be in CAPITAL letters and
+prefixed by the enum type name.
+
+Example:
+
+enum animal_type {
+	ANIMAL_TYPE_FOUR_LEGS,
+	ANIMAL_TYPE_EIGHT_LEGS,
+	ANIMAL_TYPE_TWO_LEGS,
+};
+
+If the enum contents have values (e.g. from specification) the formatting
+should be as follows:
+
+enum animal_type {
+	ANIMAL_TYPE_FOUR_LEGS =		4,
+	ANIMAL_TYPE_EIGHT_LEGS =	8,
+	ANIMAL_TYPE_TWO_LEGS =		2,
+};
+
+M10: Enum as switch variable
+============================
+
+If the variable of a switch is an enum, you must not include a default in
+switch body. The reason for this is: If later on you modify the enum by adding
+a new type, and forget to change the switch accordingly, the compiler will
+complain the new added type hasn't been handled.
+
+Example:
+
+enum animal_type {
+	ANIMAL_TYPE_FOUR_LEGS =		4,
+	ANIMAL_TYPE_EIGHT_LEGS =	8,
+	ANIMAL_TYPE_TWO_LEGS =		2,
+};
+
+enum animal_type t;
+
+switch (t) {
+case ANIMAL_TYPE_FOUR_LEGS:
+	...
+	break;
+case ANIMAL_TYPE_EIGHT_LEGS:
+	...
+	break;
+case ANIMAL_TYPE_TWO_LEGS:
+	...
+	break;
+default:  // wrong
+	break;
+}
+
+However if the enum comes from an external header file outside BlueZ, such as
+Android headers, we cannot make any assumption of how the enum is defined and
+this rule might not apply.
+
+
+M11: Always use parenthesis with sizeof
+=======================================
+
+The expression argument to the sizeof operator should always be in
+parenthesis, too.
+
+Example:
+1)
+memset(stuff, 0, sizeof(*stuff));
+
+2)
+memset(stuff, 0, sizeof *stuff); // Wrong
+
+M12: Use void if function has no parameters
+===========================================
+
+A function with no parameters must use void in the parameter list.
+
+Example:
+1)
+void foo(void)
+{
+}
+
+2)
+void foo()	// Wrong
+{
+}
+
+O1: Try to avoid complex if body
+================================
+
+It's better not to have a complicated statement for if. You may judge its
+contrary condition and return | break | continue | goto ASAP.
+
+Example:
+1)
+if (device) {  // worse
+	memset(&eir_data, 0, sizeof(eir_data));
+	if (eir_len > 0)
+		eir_parse(&eir_data, ev->eir, eir_len);
+	...
+} else {
+	error("Unable to get device object for %s", addr);
+	return;
+}
+
+2)
+if (!device) {
+	error("Unable to get device object for %s", addr);
+	return;
+}
+
+memset(&eir_data, 0, sizeof(eir_data));
+if (eir_len > 0)
+	eir_parse(&eir_data, ev->eir, eir_len);
+...