On Wed, Aug 12, 2015 at 2:23 PM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: > On Mon, 10 Aug 2015, Jassi Brar wrote: > >> On Mon, Aug 10, 2015 at 1:54 PM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: >> > On Mon, 10 Aug 2015, Jassi Brar wrote: >> >> On Mon, Jul 27, 2015 at 3:14 PM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: >> >> > This header is currently only used for defines pertaining to data >> >> > direction i.e. Rx, Tx or Loopback. >> >> > >> >> > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> >> >> > --- >> >> > include/dt-bindings/mailbox/mailbox.h | 14 ++++++++++++++ >> >> > 1 file changed, 14 insertions(+) >> >> > create mode 100644 include/dt-bindings/mailbox/mailbox.h >> >> > >> >> > diff --git a/include/dt-bindings/mailbox/mailbox.h b/include/dt-bindings/mailbox/mailbox.h >> >> > new file mode 100644 >> >> > index 0000000..82e929a >> >> > --- /dev/null >> >> > +++ b/include/dt-bindings/mailbox/mailbox.h >> >> > @@ -0,0 +1,14 @@ >> >> > +/* >> >> > + * This program is free software; you can redistribute it and/or modify >> >> > + * it under the terms of the GNU General Public License version 2 as >> >> > + * published by the Free Software Foundation. >> >> > + */ >> >> > + >> >> > +#ifndef __MAILBOX_CONTROLLER_DT_BINDINGS_H >> >> > +#define __MAILBOX_CONTROLLER_DT_BINDINGS_H >> >> > + >> >> > +#define MBOX_TX 0x1 >> >> > +#define MBOX_RX 0x2 >> >> > +#define MBOX_LOOPBACK (MBOX_RX | MBOX_TX) >> >> > + >> >> Not sure I understand 'loopback'. Does it mean h/w has some >> >> 'loopback' mode for testing purposes? Or it simply means the >> >> controller can send as well as receive messages? >> > >> > 'loopback' allows firmware to conduct some early function tests. >> > However, channels are simplex, so we provide protection against >> > multiple allocation of single channel. By allocating a LOOPBACK >> > channel we over-ride this protection and allow a single channel to be >> > allocated twice, once for Rx and the other for Tx. >> > >> So basically hardware is half-duplex, not simplex. I think maybe you >> should simply allow for RX and TX always. It should work. Just >> handover any received data before send_data (reflecting the h/w >> limitation). That way you don't need any such special flag. > > Unfortunately no, that's not correct. Only Mailbox 0 is half-duplex. > The others are simplex (Rx only). > Assuming that is indeed the case (though code and comments suggest otherwise), it is still not a matter of choice for clients to 'make' a channel RX or TX or RXTX. That is the property/constraint of the controller and the controller driver should simply check for channel ID to be zero in send_data() and return error if its non-zero. > Ideally I'd like to keep the > LOOPBACK flag, as it's easier to figure out if what someone is > attempting to do is actually valid. > I am not for such paranoia. Provider drivers is not the place to check for valid user data. The controller driver should simply reject send_data() request on any mailbox > 0 while the consumer driver should scream for attention because that's where the problem is. Please note, what I suggest will only make the code simpler while not breaking anything. Thanks. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
