On 09/10/17 17:11, Sean Young wrote:
> On Mon, Oct 09, 2017 at 11:14:28AM +0200, Hans Verkuil wrote:
>> On 05/10/17 10:45, Sean Young wrote:
> -snip-
>>> +/*
>>> + * struct lirc_scancode - decoded scancode with protocol for use with
>>> + * LIRC_MODE_SCANCODE
>>> + *
>>> + * @timestamp: Timestamp in nanoseconds using CLOCK_MONOTONIC when IR
>>> + * was decoded.
>>> + * @flags: should be 0 for transmit. When receiving scancodes,
>>> + * LIRC_SCANCODE_FLAG_TOGGLE or LIRC_SCANCODE_FLAG_REPEAT can be set
>>> + * depending on the protocol
>>> + * @target: target for transmit. Unused, set to 0.
>>> + * @source: source for receive. Unused, set to 0.
>>> + * @unused: set to 0.
>>> + * @rc_proto: see enum rc_proto
>>> + * @scancode: the scancode received or to be sent
>>> + */
>>> +struct lirc_scancode {
>>> + __u64 timestamp;
>>> + __u32 flags;
>>> + __u8 target;
>>> + __u8 source;
>>> + __u8 unused;
>>> + __u8 rc_proto;
>>> + __u64 scancode;
>>
>> I'm thinking how this will be implemented using CEC. Some RC commands take arguments
>> (up to 4 bytes for the 0x67 (Tune Function) code), so how will they be handled?
>>
>> See CEC table 6 in the HDMI 1.4 spec.
>>
>> Should they be part of the scancode, or would it be better to add a '__u8 args[8];'
>> field?
>>
>> I've no idea what makes sense, it's a weird corner case.
>
> I've given it some more thought.
>
> For cec remote control passthrough, you have the tv with the IR receiver (A),
> which then transmits CEC_MSG_USER_CONTROL_PRESSED and
> CEC_MSG_USER_CONTROL_RELEASED cec messages to the correct target, with
> arguments. Then on the target (B), it reads those commands and should execute
> them as if it received them itself.
>
> First of all (B) is already implemented in cec using rc-core. If RC
> passthrough is enabled, then cec will pass those keycodes to rc-core (which
> end up in an input device).
>
> So the problem we are trying to solve here is (A). How I would see this
> implemented is:
>
> 1) A physical IR receiver exists which has an rc-core driver and a /dev/lircN
> device. This is configured using ir-keytable to map to regular input events
>
> 2) A process receives input events, and decides that a particular key/command
> is not for itself (e.g. tell top set box to tune), so it knows what the
> target cec address is and the tune arguments, so it fills out a
> cec_msg with the target, CEC_MSG_USER_CONTROL_PRESSED, 0x67, arguments,
> and then transmits it using the ioctl CEC_TRANSMIT, followed by
> another CEC_MSG_USER_CONTROL_RELEASED cec_msg sent using ioctl CEC_TRANSMIT.
>
> In this way of viewing things, an rc-core device is either cec or lirc, and
> thus rc-core lirc devices have a /dev/lircN and rc-core cec devices have a
> /dev/cecN.
>
> So, the alternative which is being proposed is that a cec device has both
> a /dev/cecN and a /dev/lircN. In this case step 2) would look like:
>
> 2) A process receives input events, and decides that a particular key/command
> is not for itself (e.g. tell top set box to tune), so it knows what the
> target cec address is and the tune arguments, so it fills in a
> lirc_scancode with the target, CEC_MSG_USER_CONTROL_PRESSED, 0x67, arguments,
> and then transmits it using write() to the /dev/lircN device, which
> then passes it on to cec_transmit() in drivers/media/cec/cec-api.c
> (without having a cec_fh), and then another lirc_scancode is
> filled in CEC_MSG_USER_CONTROL_RELEASED and sent.
>
> Now, I think that this has a number of problems:
>
> - It's a lot of API for simply doing a CEC_TRANSMIT
>
> - and another chardev for a cec device (i.e. /dev/lircN).
>
> - lirc scancode tx deals with scancodes, for cec rc passthrough it isn't
> really scancodes.
>
> - Wiring this up is not going to be pretty or easy.
>
> - The lirc chardev has no other function other than sending
> CEC_MSG_USER_CONTROL_PRESSED and CEC_MSG_USER_CONTROL_RELEASED cec messages.
>
> So what I am proposing is that we don't use lirc for sending rc passthrough
> messages for cec.
>
> I hope this makes sense and where not, please *do* tell me exactly where I
> am wrong. I think that I missed something about the scancode tx idea.
You are right, it makes no sense. Let's forget about this.
Regards,
Hans
>
>>
>>> +};
>>> +
>>> +#define LIRC_SCANCODE_FLAG_TOGGLE 1
>>> +#define LIRC_SCANCODE_FLAG_REPEAT 2
>>
>> These flags need documentation.
>
> They do, fair point.
>
> Thanks,
>
> Sean
>
