Re: /dev/psaux-Interface

[Sau Dan Lee]

>>>>> "Dmitry" == Dmitry Torokhov <dtor_core@xxxxxxxxxxxxx> writes:

    Dmitry> OK, here you go. It is the first cut. The driver creates
    Dmitry> an absolute device for the touchscreen and a fake
    Dmitry> pass-through port to for the pointing device which works
    Dmitry> in relative mode. All fancy stuff can be done in userspace
    Dmitry> via evdev.

I  still  haven't  tried  it.   But upon  first  inspection,  I  found
something undesirable already.

+static void lbtouch_pass_pt_packet(struct serio *ptport, unsigned char *packet)
+{
+	struct psmouse *child = ptport->private;
+
+	if (child && child->state == PSMOUSE_ACTIVATED) {
+		serio_interrupt(ptport, packet[0], 0, NULL);
+		serio_interrupt(ptport, packet[1], 0, NULL);
+		serio_interrupt(ptport, packet[2], 0, NULL);
+	}
+}
+

So,  you're  imposing the  policy  that  the  packets must  as  3-byte
packets?  My  experiences in  writing my XFree86  driver is  that some
bytes  are sometimes  dropped, for  reasons I  don't know.   My driver
would  attempt to  resync, although  not reliably  because  the packet
format   in   touch-screen   mode   does  not   provide   a   reliable
synchronization mechanism (such  as parity, a special bit  to mark the
end of a packet, etc.).

I don't know whether the dropping  of bytes is specific to my machine,
or is common to all B142 models.


+static psmouse_ret_t lbtouch_process_byte(struct psmouse *psmouse, struct pt_regs *regs)
+{
+	struct input_dev *dev = &psmouse->dev;
+	unsigned char *p = psmouse->packet;
+	int x, y, touch;
+
+	input_regs(dev, regs);
+
+	if (psmouse->pktcnt < 3)
+		return PSMOUSE_GOOD_DATA;
+

The  same problem.   You  wait  for a  complete  3-byte packet  before
emitting an event.  What happens to dropped bytes?


And what  happens to the timeout  feature in my  XFree86 driver?  That
feature is  the main reason I  write my driver, because  that's what I
want and  couldn't find (in others' implementation  of the touchscreen
driver).  The feature could be either in a XFree86 driver, or a kernel
mouse driver.  But I'm not going to write another XFree86 driver.  The
feature is already there in my  XFree86 driver, and I just want direct
byte-level  communication  to the  PSAUX  port.   No 3-byte  boundarys
imposed.  No censoring of data in either direction.  It's that simple.
What make that so difficult?



-- 
Sau Dan LEE                     ???(Big5)                    ~{@nJX6X~}(HZ) 

E-mail: danlee@xxxxxxxxxxxxxxxxxxxxxxxxxx
Home page: http://www.informatik.uni-freiburg.de/~danlee

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