Hi!

We can make use of serdev drivers to do simple device drivers for
TS 27.010 chanels, and we can handle vendor specific protocols on top
of TS 27.010 with serdev drivers.

So far this has been tested with Motorola droid4 where there is a custom
packet numbering protocol on top of TS 27.010 for the MDM6600 modem.

I initially though about adding the serdev support into a separate file,
but that will take some refactoring of n_gsm.c. And I'd like to have
things working first. Then later on we might want to consider splitting
n_gsm.c into three pieces for core, tty and serdev parts. And then maybe
the serdev related parts can be just moved to live under something like
drivers/tty/serdev/protocol/ngsm.c.

Signed-off-by: Tony Lindgren <tony@atomide.com>

If you fix error path below, you can add:

Reviewed-by: Pavel Machek <redacted> 

+static struct gsm_dlci *gsd_dlci_get(struct gsm_serdev *gsd, int line,
+				     bool allocate)
+{
+	struct gsm_mux *gsm;
+	struct gsm_dlci *dlci;
+
+	if (!gsd || !gsd->gsm)
+		return ERR_PTR(-ENODEV);
+
+	gsm = gsd->gsm;
+
+	if (line < 1 || line >= 63)
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&gsm->mutex);

...

+	dlci = gsm_dlci_alloc(gsm, line);
+	if (!dlci) {
+		gsm = ERR_PTR(-ENOMEM);
+		goto unlock;

dlci = , or you get nice crash.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html