* Issue using kernel linked list in user space
@ 2015-09-19 16:56 Gunjan Mehta
2015-09-20 7:05 ` Pranay Srivastava
0 siblings, 1 reply; 3+ messages in thread
From: Gunjan Mehta @ 2015-09-19 16:56 UTC (permalink / raw)
To: kernelnewbies
I have a linked list like this http://pastebin.com/bwF3jLb6 . The problem i
am facing is i have initialized the list head and
then i am doing malloc for that struct object. What i need is i want to
make struct abc_st *r as head of linked list and other nodes after it.
typedef struct abc {
char client_id[18];
char mac[18];
st_list_head list;
}abc_st;
abc_st* check_fields (abc_st *ptr)
{
char cmd[500];
MYSQL_RES *result;
MYSQL_ROW row;
int num_rows;
abc_st *r=NULL,*temp=NULL;
INIT_LIST_HEAD(&r->list); // i have intialized the head here
sprintf(cmd, "SELECT * FROM ABCD_TABLE WHERE MAC = %.4x", ptr->mac);
/* Running the sql query to check for fields with value in database
*/
if (mysql_query(abc_db.db_handle, cmd)) {
num_rows = -1;
goto done;
}
result = mysql_store_result(abc_db.db_handle);
if (result == NULL) {
num_rows = -1;
goto done;
}
num_rows = mysql_num_rows(result);
while ((row = mysql_fetch_row(result)))
{
r= (abc_st *)malloc(sizeof(abc_st));
memcpy(r->mac,row[1],strlen(row[1])+1);
memcpy(r->client_id,row[0],strlen(row[0])+1);
How should i use list_add ?
//list_add(struct list_head *new, struct list_head *head)
//prototype of list_add
// list_add(&temp->list,&r->list); //it will go wrong here, i want
to make r(structure r as head and then add other strutcure objects)
// r->link = NULL;
//list_add(r, ptr);
}
done:
mysql_free_result(result);
return r;
}
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Issue using kernel linked list in user space
2015-09-19 16:56 Issue using kernel linked list in user space Gunjan Mehta
@ 2015-09-20 7:05 ` Pranay Srivastava
2015-09-21 6:56 ` Pravin Shedage
0 siblings, 1 reply; 3+ messages in thread
From: Pranay Srivastava @ 2015-09-20 7:05 UTC (permalink / raw)
To: kernelnewbies
On Sat, Sep 19, 2015 at 10:26 PM, Gunjan Mehta <gunjanmehta08@gmail.com> wrote:
> I have a linked list like this http://pastebin.com/bwF3jLb6 . The problem i
> am facing is i have initialized the list head and
> then i am doing malloc for that struct object. What i need is i want to
> make struct abc_st *r as head of linked list and other nodes after it.
>
> typedef struct abc {
> char client_id[18];
> char mac[18];
> st_list_head list;
> }abc_st;
>
> abc_st* check_fields (abc_st *ptr)
> {
> char cmd[500];
> MYSQL_RES *result;
> MYSQL_ROW row;
> int num_rows;
> abc_st *r=NULL,*temp=NULL;
huh? this is initialized?
> INIT_LIST_HEAD(&r->list); // i have intialized the head here
>
> sprintf(cmd, "SELECT * FROM ABCD_TABLE WHERE MAC = %.4x", ptr->mac);
> /* Running the sql query to check for fields with value in database
> */
> if (mysql_query(abc_db.db_handle, cmd)) {
> num_rows = -1;
> goto done;
> }
> result = mysql_store_result(abc_db.db_handle);
> if (result == NULL) {
> num_rows = -1;
> goto done;
> }
> num_rows = mysql_num_rows(result);
>
> while ((row = mysql_fetch_row(result)))
> {
> r= (abc_st *)malloc(sizeof(abc_st));
> memcpy(r->mac,row[1],strlen(row[1])+1);
> memcpy(r->client_id,row[0],strlen(row[0])+1);
> How should i use list_add ?
> //list_add(struct list_head *new, struct list_head *head)
> //prototype of list_add
> // list_add(&temp->list,&r->list); //it will go wrong here, i want
> to make r(structure r as head and then add other strutcure objects)
> // r->link = NULL;
> //list_add(r, ptr);
>
> }
> done:
> mysql_free_result(result);
>
> return r;
>
> }
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
--
---P.K.S
^ permalink raw reply [flat|nested] 3+ messages in thread
* Issue using kernel linked list in user space
2015-09-20 7:05 ` Pranay Srivastava
@ 2015-09-21 6:56 ` Pravin Shedage
0 siblings, 0 replies; 3+ messages in thread
From: Pravin Shedage @ 2015-09-21 6:56 UTC (permalink / raw)
To: kernelnewbies
On Sun, Sep 20, 2015 at 12:35 PM, Pranay Srivastava <pranjas@gmail.com>
wrote:
> On Sat, Sep 19, 2015 at 10:26 PM, Gunjan Mehta <gunjanmehta08@gmail.com>
wrote:
>> I have a linked list like this http://pastebin.com/bwF3jLb6 . The
problem i
>> am facing is i have initialized the list head and
>> then i am doing malloc for that struct object. What i need is i want to
>> make struct abc_st *r as head of linked list and other nodes after it.
>>
>> typedef struct abc {
>> char client_id[18];
>> char mac[18];
>> st_list_head list;
>> }abc_st;
>>
>> abc_st* check_fields (abc_st *ptr)
>> {
>> char cmd[500];
>> MYSQL_RES *result;
>> MYSQL_ROW row;
>> int num_rows;
>> abc_st *r=NULL,*temp=NULL;
>
> huh? this is initialized?
>> INIT_LIST_HEAD(&r->list); // i have intialized the head here
>
>>
>> sprintf(cmd, "SELECT * FROM ABCD_TABLE WHERE MAC = %.4x", ptr->mac);
>> /* Running the sql query to check for fields with value in
database
>> */
>> if (mysql_query(abc_db.db_handle, cmd)) {
>> num_rows = -1;
>> goto done;
>> }
>> result = mysql_store_result(abc_db.db_handle);
>> if (result == NULL) {
>> num_rows = -1;
>> goto done;
>> }
>> num_rows = mysql_num_rows(result);
>>
>> while ((row = mysql_fetch_row(result)))
>> {
>> r= (abc_st *)malloc(sizeof(abc_st));
>> memcpy(r->mac,row[1],strlen(row[1])+1);
>> memcpy(r->client_id,row[0],strlen(row[0])+1);
>> How should i use list_add ?
>> //list_add(struct list_head *new, struct list_head *head)
>> //prototype of list_add
>> // list_add(&temp->list,&r->list); //it will go wrong here, i
want
>> to make r(structure r as head and then add other strutcure objects)
>> // r->link = NULL;
>> //list_add(r, ptr);
>>
>> }
>> done:
>> mysql_free_result(result);
>>
>> return r;
>>
>> }
>>
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies at kernelnewbies.org
>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>
>
>
>
> --
> ---P.K.S
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
INIT_LIST_HEAD gets a struct list head * and initializes list->next &
list->prev.
Use calloc to initialize other members from struct abc.
st_list_head list;
I hope this will be typedef of struct list_head.
INIT_LIST_HEAD(&r->list); <-- This indicate r as a List Head.
Just small change you need. r remains be your list head. To add new node,
create newnode of type (abc_st *) and add it in the list.
check the code modification which clarify you better.
typedef struct abc {
char client_id[18];
char mac[18];
st_list_head list;
}abc_st;
abc_st* check_fields (abc_st *ptr)
{
char cmd[500];
MYSQL_RES *result;
MYSQL_ROW row;
int num_rows;
abc_st *r=NULL,*temp=NULL;
abc_st *newnode = NULL;
INIT_LIST_HEAD(&r->list); // i have intialized the head here
sprintf(cmd, "SELECT * FROM ABCD_TABLE WHERE MAC = %.4x", ptr->mac);
/* Running the sql query to check for fields with value in database
*/
if (mysql_query(abc_db.db_handle, cmd)) {
num_rows = -1;
goto done;
}
result = mysql_store_result(abc_db.db_handle);
if (result == NULL) {
num_rows = -1;
goto done;
}
num_rows = mysql_num_rows(result);
while ((row = mysql_fetch_row(result)))
{
if ((newnode = (abc_st *)calloc(sizeof(abc_st))) == NULL) {
fprintf(stderr, "%s\n", strerror(errno));
goto done;
}
memcpy(newnode->mac,row[1],strlen(row[1])+1);
memcpy(newnode->client_id,row[0],strlen(row[0])+1);
list_add(&(newnode->list), &(r->list));
}
done:
mysql_free_result(result);
return r;
}
- Thanks & Regards,
PraviN
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2015-09-19 16:56 Issue using kernel linked list in user space Gunjan Mehta
2015-09-20 7:05 ` Pranay Srivastava
2015-09-21 6:56 ` Pravin Shedage
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