On Aug 5, 2009, at 9:34 AM, Robert P. J. Day wrote:
i'm still somewhat confused here. in every example using a seq_file
that i've ever seen, it's *assumed* that the very first call to the
start() routine is going to pass a (*pos) value of zero, which is used
to signify the initial call to that start routine. that *has* to be
consistent. if it can be something other than zero for that *initial*
call, how would seq_files ever be guaranteed to work properly?
I pulled this from fs/proc/devices.c, I hope it's version compatible
with your query:
static void *devinfo_start(struct seq_file *f, loff_t *pos)
27 {
28 if (*pos < (BLKDEV_MAJOR_HASH_SIZE +
CHRDEV_MAJOR_HASH_SIZE))
29 return pos;
30 return NULL;
31 }
This example does not assume (*pos) is initialized to zero. Digging
further back into the sequence of events that occurs before the
start() is called, I can't find anything that explicitly sets the
(*pos) to zero, unless it follows philosophy of setting (*pos) to zero
when open() is called (this is probably buried in the more generic
file I/O layers).
-Bruce
