Thanks, Andrew, for your review. Some replies:

Am 02.02.2007 02:13 schrieb Andrew Morton:

On Thu, 1 Feb 2007 22:12:24 +0100
Tilman Schmidt [off-list ref] wrote:

quoted

+/* Kbuild sometimes doesn't set this */
+#ifndef KBUILD_MODNAME
+#define KBUILD_MODNAME "asy_gigaset"
+#endif

That's a subtle way of reporting a kbuild bug ;)

What's the story here?

If an object file is linked into more than one module (like
asyncdata.o which is linked into both ser_gigaset and usb_gigaset)
then Kbuild compiles it only once but cannot decide which of the
module names to put into KBUILD_MODNAME, so it takes the easy way
out and doesn't define KBUILD_MODNAME at all. I'm not sure if
that qualifies as a kbuild bug. I'd rather call it a limitation.

quoted

+static int write_modem(struct cardstate *cs)
+{
+	struct tty_struct *tty = cs->hw.ser->tty;
+	struct bc_state *bcs = &cs->bcs[0];	/* only one channel */
+	struct sk_buff *skb = bcs->tx_skb;
+	int sent;
+
+	if (!tty || !tty->driver || !skb)
+		return -EFAULT;

Is EFAULT appropriate?

It hardly matters, as it isn't propagated anywhere. -1 would
work just as well.

Can all these things happen?

Theoretically no, but this is called from a tasklet and I have
already traced a bug which made one of these disappear. Not
having the kernel crash completely in such an event considerably
helps debugging.

quoted

+	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

Is a client of the tty interface supposed to be diddling tty flags like this?

Documentation/tty.txt says so. (Yes, I wrote that part myself,
but nobody protested. ;-) Also, the PPP line discipline does
the same.

quoted

+	spin_lock_irqsave(&cs->cmdlock, flags);
+	cb = cs->cmdbuf;
+	spin_unlock_irqrestore(&cs->cmdlock, flags);

It is doubtful if the locking here does anything useful.

It assures atomicity when reading the cs->cmdbuf pointer.

quoted

+	spin_lock_irqsave(&cs->cmdlock, flags);
+	cb->prev = cs->lastcmdbuf;
+	if (cs->lastcmdbuf)
+		cs->lastcmdbuf->next = cb;
+	else {
+		cs->cmdbuf = cb;
+		cs->curlen = len;
+	}
+	cs->cmdbytes += len;
+	cs->lastcmdbuf = cb;
+	spin_unlock_irqrestore(&cs->cmdlock, flags);

Would the use of list_heads simplify things here?

I don't think so. The operations in list.h do not keep track of
the total byte count, and adding that in a race-free way appears
non-trivial.

quoted

+/*
+ * Free hardware specific device data
+ * This will be called by "gigaset_freecs" in common.c
+ */
+static void gigaset_freecshw(struct cardstate *cs)
+{
+	tasklet_kill(&cs->write_tasklet);

Does tasklet kill() wait for the tasklet to stop running on a different
CPU?  I thing so, but it was written in the days before we commented code.

Its description in LDD3 ch. 7 seems to imply that it does.

quoted

+			down(&cs->hw.ser->dead_sem);

Does this actually use the semaphore's counting feature?  If not, can we
switch it to a mutex?

I stole that code from the PPP line discipline. It is to assure all
other ldisc methods have completed before the close method proceeds.
This doesn't look like a case for a mutex to me, but I'm open to
suggestions if it's important to avoid a semaphore here.

quoted

+	tail = atomic_read(&inbuf->tail);
+	head = atomic_read(&inbuf->head);
+	gig_dbg(DEBUG_INTR, "buffer state: %u -> %u, receive %u bytes",
+		head, tail, count);
+
+	if (head <= tail) {
+		n = RBUFSIZE - tail;
+		if (count >= n) {
+			/* buffer wraparound */
+			memcpy(inbuf->data + tail, buf, n);
+			tail = 0;
+			buf += n;
+			count -= n;
+		} else {
+			memcpy(inbuf->data + tail, buf, count);
+			tail += count;
+			buf += count;
+			count = 0;
+		}
+	}

Perhaps the (fairly revolting) circ_buf.h can be used for this stuff.

It probably could, but IMHO readability would suffer rather than improve.

Thanks,
Tilman

PS: My patch hasn't appeared on LKML so far. Any idea why?

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
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