link list implementation in linux kernel easy question syntax not clear

2010-10-09 Thread Bond 
Hi,in
http://lxr.linux.no/#linux+v2.6.18/include/linux/list.h
following section of code
there is a structure which is defined as

struct list_head {
struct list_head *next, *prev;
};

It is used in another file as

#define LIST_HEAD_INIT(name) { (name), (name) }

#define LIST_HEAD(name) \
struct list_head name = LIST_HEAD_INIT(name)

static inline void INIT_LIST_HEAD(struct list_head *list)
{
list-next = list;
list-prev = list;
}


I came across a book where the code is given as follows in an example

include/linux/list.h
struct list_head {
struct list_head *next,*prev;
};
#define LIST_HEAD_INIT(name) {(name),(name)}

#define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)
#define INIT_LIST_HEAD(prt) do {\
(ptr)-next = (ptr);(ptr)-prev= (ptr);\
}while(0)


I was not able to understand above code segment.
I am aware of what a #define is but still I could not understand above thing.
Can some one help in understanding with some example.
Not related to Linux Kernel a normal example where I
can make a link list with above defined way.


-- 
http://vger.kernel.org/vger-lists.html

--
To unsubscribe from this list: send an email with
unsubscribe kernelnewbies to ecar...@nl.linux.org
Please read the FAQ at http://kernelnewbies.org/FAQ

Re: link list implementation in linux kernel easy question syntax not clear

2010-10-09 Thread Manish Katiyar 
On Fri, Oct 8, 2010 at 11:38 PM, Bond jamesbond.2...@gmail.com wrote:
 Hi,in
 http://lxr.linux.no/#linux+v2.6.18/include/linux/list.h
 following section of code
 there is a structure which is defined as

 struct list_head {
        struct list_head *next, *prev;
 };

 It is used in another file as

 #define LIST_HEAD_INIT(name) { (name), (name) }

 #define LIST_HEAD(name) \
        struct list_head name = LIST_HEAD_INIT(name)

 static inline void INIT_LIST_HEAD(struct list_head *list)
 {
        list-next = list;
        list-prev = list;
 }


 I came across a book where the code is given as follows in an example

 include/linux/list.h
 struct list_head {
 struct list_head *next,*prev;
 };
 #define LIST_HEAD_INIT(name) {(name),(name)}

 #define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)
 #define INIT_LIST_HEAD(prt) do {\
 (ptr)-next = (ptr);(ptr)-prev= (ptr);\
 }while(0)


 I was not able to understand above code segment.
 I am aware of what a #define is but still I could not understand above thing.
 Can some one help in understanding with some example.
 Not related to Linux Kernel a normal example where I
 can make a link list with above defined way.

http://kernelnewbies.org/FAQ/LinkedLists



 --
 http://vger.kernel.org/vger-lists.html

 --
 To unsubscribe from this list: send an email with
 unsubscribe kernelnewbies to ecar...@nl.linux.org
 Please read the FAQ at http://kernelnewbies.org/FAQ





-- 
Thanks -
Manish
==
[$\*.^ -- I miss being one of them
==

--
To unsubscribe from this list: send an email with
unsubscribe kernelnewbies to ecar...@nl.linux.org
Please read the FAQ at http://kernelnewbies.org/FAQ

Re: link list implementation in linux kernel easy question syntax not clear

2010-10-09 Thread Bond 
On Sat, Oct 9, 2010 at 12:27 PM, Manish Katiyar mkati...@gmail.com wrote:
 On Fri, Oct 8, 2010 at 11:38 PM, Bond jamesbond.2...@gmail.com wrote:
 Hi,in
 http://lxr.linux.no/#linux+v2.6.18/include/linux/list.h
 following section of code
 there is a structure which is defined as

 struct list_head {
        struct list_head *next, *prev;
 };

 It is used in another file as

 #define LIST_HEAD_INIT(name) { (name), (name) }

 #define LIST_HEAD(name) \
        struct list_head name = LIST_HEAD_INIT(name)

 static inline void INIT_LIST_HEAD(struct list_head *list)
 {
        list-next = list;
        list-prev = list;
 }


 I came across a book where the code is given as follows in an example

 include/linux/list.h
 struct list_head {
 struct list_head *next,*prev;
 };
 #define LIST_HEAD_INIT(name) {(name),(name)}

 #define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)
 #define INIT_LIST_HEAD(prt) do {\
 (ptr)-next = (ptr);(ptr)-prev= (ptr);\
 }while(0)


 I was not able to understand above code segment.
 I am aware of what a #define is but still I could not understand above thing.
 Can some one help in understanding with some example.
 Not related to Linux Kernel a normal example where I
 can make a link list with above defined way.

 http://kernelnewbies.org/FAQ/LinkedLists


I read that link but could not understand much out of it.

--
To unsubscribe from this list: send an email with
unsubscribe kernelnewbies to ecar...@nl.linux.org
Please read the FAQ at http://kernelnewbies.org/FAQ

Re: link list implementation in linux kernel easy question syntax not clear

2010-10-09 Thread shivanth m p 
On Sat, Oct 9, 2010 at 6:16 PM, Bond jamesbond.2...@gmail.com wrote:

 On Sat, Oct 9, 2010 at 12:27 PM, Manish Katiyar mkati...@gmail.com
 wrote:
  On Fri, Oct 8, 2010 at 11:38 PM, Bond jamesbond.2...@gmail.com wrote:
  Hi,in
  http://lxr.linux.no/#linux+v2.6.18/include/linux/list.h
  following section of code
  there is a structure which is defined as
 
  struct list_head {
 struct list_head *next, *prev;
  };
 
  It is used in another file as
 
  #define LIST_HEAD_INIT(name) { (name), (name) }
 
  #define LIST_HEAD(name) \
 struct list_head name = LIST_HEAD_INIT(name)
 
  static inline void INIT_LIST_HEAD(struct list_head *list)
  {
 list-next = list;
 list-prev = list;
  }
 
 
  I came across a book where the code is given as follows in an example
 
  include/linux/list.h
  struct list_head {
  struct list_head *next,*prev;
  };
  #define LIST_HEAD_INIT(name) {(name),(name)}
 
  #define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)
  #define INIT_LIST_HEAD(prt) do {\
  (ptr)-next = (ptr);(ptr)-prev= (ptr);\
  }while(0)
 
 
  I was not able to understand above code segment.
  I am aware of what a #define is but still I could not understand above
 thing.
  Can some one help in understanding with some example.
  Not related to Linux Kernel a normal example where I
  can make a link list with above defined way.
 
  0
 
 
 I read that link but could not understand much out of it.

 --
 To unsubscribe from this list: send an email with
 unsubscribe kernelnewbies to ecar...@nl.linux.org
 Please read the FAQ at http://kernelnewbies.org/FAQ


The list_head structure here is used inside your structure which's used as
the nodes for linked list .

 Whenever you are going to create a node for your list , all the pointers
next and prev are initialized to point to itself.This is what
INIT_LIST_HEAD
does
.
But the same task can be done at compile time by using the maco
LIST_HEAD_INIT()

In fact both of them are used for the same task .

Now We need a starting point for the list . This variable points to the
first element of the list. We use the variable of type   list_head to
accomplish this . this is often used as  a local variable so that you can do
it anywhere in your kernel  .

So to initialize this we use the macro LIST_HEAD()

we add elements to this list using the list_add function( api you could call
it)