I got it. The correct way to pull out a struct from the kfifo, could be: rc = kfifo_out(&pfops->mymod_fifo, &r_cache1, sizeof(struct mymod_data_pkt)); BR Christian
hello, Im struggle with a simple kfifo. I try to do it dynamicly. For the sake of simplicity I changed the code in a way that everything with the kfifo is done in the open function of my module.
First of all, I have a struct, in which I store the pointer to that kfifo:
struct mymod_private_fops { wait_queue_head_t wait; struct kfifo mymod_fifo; }
And the struct in which I store my data:
struct mymod_data_pkt { __u8 mbyte; __u8 smfunc; ktime_t ktime; __u16 len; __u16 sequence; char devname[32] void *page; };
this is the open function, which creates the kfifo and stores the pointer to that kfifo for later usage. As I mentioned I simplified the whole thing to have the store operation into the kfifo and the fetch operation, out of the kfifo in one place. Initially I did this in the read and write function.
static int mymod_open(struct inode *pinode, struct file *pfile) { int rc = 0, len = 0;
struct mymod_private_fops pfops; struct mymod_data_pkt w_cache1, w_cache2, w_cache3 r_cache1, r_cache2, r_cache3;
pfops = kzalloc(sizeof(struct mymod_private_fops), GFP_KERNEL);
if(pfops == NULL) return -ENOMEM;
init_waitqueue_head(&pfops->wait);
len = LOG_STACK_SIZE * sizeof(struct mymod_data_pkt);
rc = kfifo_alloc(&pfops->mymod_fifo, len, GFP_KERNEL); if(rc) { pr_err("kfifo_alloc failed %d", rc); return rc; }
if(! kfifo_initialized(&pfops->mymod_fifo)) { pr_err("kfifo initialized"); }
w_cache1.mbyte = 4; w_cache1.len = 245;
rc = kfifo_in(&pfops->mymod_fifo, &w_cache1, sizeof(struct mymod_data_pkt)); pr_err("kfifo_in returns %d", rc);
w_cache2.mbyte = 42; w_cache2.len = 112;
rc = kfifo_in(&pfops->mymod_fifo, &w_cache2, sizeof(struct mymod_data_pkt)); pr_err("kfifo_in returns %d", rc);
w_cache3.mbyte = 119; w_cache3.len = 77;
rc = kfifo_in(&pfops->mymod_fifo, &w_cache3, sizeof(struct mymod_data_pkt)); pr_err("kfifo_in returns %d", rc);
rc = kfifo_len(&pfops->mymod_fifo); pr_err("kfifo_len: %d", rc);
memset(&r_cache1, 0, sizeof(struct mymod_data_pkt));
rc = kfifo_get(&pfops->mymod_fifo, &r_cache1); pr_err("kfifo_get returns %d", rc);
pr_err("content of kfifo r_cache1->mbyte: %d", r_cache1.mbyte);
memset(&r_cache2, 0, sizeof(struct mymod_data_pkt));
rc = kfifo_get(&pfops->mymod_fifo, &r_cache2); pr_err("kfifo_get returns %d", rc);
pr_err("content of kfifo r_cache2->mbyte: %d", r_cache2.mbyte);
...
pfile->private_data = pfops;
...
[ 108.200977] kfifo_in returns 64 [ 108.200985] kfifo_in returns 64 [ 108.200990] kfifo_in returns 64 [ 108.200993] kfifo_len: 192 [ 108.200997] kfifo_get returns 1 [ 108.201000] content of kfifo r_cache1->mbyte: 4 [ 108.201003] kfifo_get returns 1 [ 108.201006] content of kfifo r_cache2->mbyte: 0 [ 108.201010] kfifo_get returns 1 [ 108.201013] content of kfifo r_cache3->mbyte: 0
The initialization worked fine, the store operations went properly. Only pulling data out of the kfifo didn't work as expected. Only the 1st element was correct, the 2nd and 3rd element was just 0
Also the size of the struct and the fifo seems to be okay. The struct has the size of 64 (there is some padding within I think) and after inserting 3 elements the kfifo has the size of 192
Where is the flaw here?
Thank you in advance
Best regards Christian
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