Re: [PATCH 1/2 v3] emulator: add codec negotiation support

[Denis Kenzior <denkenz@gmail.com>]

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Hi Simon,

On 10/21/2015 02:42 AM, Simon Fels wrote:
> Hey Denis,
>
>> Please make sure not to go over 80 chars / line.  Even if you need to
>> indent arguments 2-4 less than what is required by our style guidelines.
>
> vim shows me I am at 76 chars with having 4 spaces per tab. So how many
> spaces do you take per tab to come over 80 chars? 8 spaces?
>

We use kernel coding style, so yes, 8 spaces.

>>> +
>>>   #ifdef __cplusplus
>>>   }
>>>   #endif
>>> diff --git a/src/emulator.c b/src/emulator.c
>>> index 626dec3..e16312e 100644
>>> --- a/src/emulator.c
>>> +++ b/src/emulator.c
>>> @@ -27,6 +27,7 @@
>>>   #include <string.h>
>>>   #include <unistd.h>
>>>   #include <stdbool.h>
>>> +#include <errno.h>
>>>
>>>   #include <glib.h>
>>>
>>> @@ -39,6 +40,15 @@
>>>
>>>   #define RING_TIMEOUT 3
>>>
>>> +#define CVSD_OFFSET 0
>>> +#define MSBC_OFFSET 1
>>> +#define CODECS_COUNT (MSBC_OFFSET + 1)
>>> +
>>> +struct hfp_codec_info {
>>> +    unsigned char type;
>>> +    ofono_bool_t supported;
>>> +};
>>> +
>>>   struct ofono_emulator {
>>>       struct ofono_atom *atom;
>>>       enum ofono_emulator_type type;
>>> @@ -50,6 +60,13 @@ struct ofono_emulator {
>>>       guint callsetup_source;
>>>       int pns_id;
>>>       struct ofono_handsfree_card *card;
>>> +    struct hfp_codec_info r_codecs[CODECS_COUNT];
>>> +    unsigned char negotiated_codec;
>>> +    unsigned char proposed_codec;
>>> +    guint delay_sco;
>>
>> Is this still needed?
>>
>>> +    ofono_emulator_codec_negotiation_cb codec_negotiation_cb;
>>> +    void *codec_negotiation_data;
>>> +    ofono_bool_t bac_received;
>>>       bool slc : 1;
>>>       unsigned int events_mode : 2;
>>>       bool events_ind : 1;
>>> @@ -938,6 +955,168 @@ fail:
>>>       }
>>>   }
>>>
>>> +static void bac_cb(GAtServer *server, GAtServerRequestType type,
>>> +            GAtResult *result, gpointer user_data)
>>> +{
>>> +    struct ofono_emulator *em = user_data;
>>> +    GAtResultIter iter;
>>> +    int val;
>>> +
>>> +    DBG("");
>>> +
>>> +    switch (type) {
>>> +    case G_AT_SERVER_REQUEST_TYPE_SET:
>>> +        g_at_result_iter_init(&iter, result);
>>> +        g_at_result_iter_next(&iter, "");
>>> +
>>> +        /*
>>> +         * CVSD codec is mandatory and must come first.
>>> +         * See HFP v1.6 4.34.1
>>> +         */
>>> +        if (g_at_result_iter_next_number(&iter, &val) == FALSE ||
>>> +                val != HFP_CODEC_CVSD)
>>> +            goto fail;
>>> +
>>> +        em->bac_received = TRUE;
>>> +
>>> +        em->negotiated_codec = 0;
>>> +        em->r_codecs[CVSD_OFFSET].supported = TRUE;
>>> +
>>> +        while (g_at_result_iter_next_number(&iter, &val)) {
>>> +            switch (val) {
>>> +            case HFP_CODEC_MSBC:
>>> +                em->r_codecs[MSBC_OFFSET].supported = TRUE;
>>> +                break;
>>> +            default:
>>> +                DBG("Unsupported HFP codec %d", val);
>>> +                break;
>>> +            }
>>> +        }
>>> +
>>> +        g_at_server_send_final(server, G_AT_SERVER_RESULT_OK);
>>> +
>>> +        /*
>>> +         * If we're currently in the process of selecting a codec
>>> +         * we have to restart that now
>>> +         */
>>> +        if (em->proposed_codec)
>>> +            ofono_emulator_start_codec_negotiation(em, 0, NULL, NULL);
>>> +
>>> +        break;
>>> +
>>> +    default:
>>> +fail:
>>> +        DBG("Process AT+BAC failed");
>>> +        g_at_server_send_final(server, G_AT_SERVER_RESULT_ERROR);
>>
>> In theory our codec-negotiation procedure might have failed, do we want
>> to call the callback here as well?
>>
>>> +        break;
>>> +    }
>>> +}
>>> +
>>> +static void finish_codec_negotiation(struct ofono_emulator *em,
>>> +            int err)
>>> +{
>>> +    if (em->codec_negotiation_cb == NULL)
>>> +        return;
>>> +
>>> +    em->codec_negotiation_cb(err, em->codec_negotiation_data);
>>> +
>>> +    em->codec_negotiation_cb = NULL;
>>> +    em->codec_negotiation_data = NULL;
>>> +}
>>> +
>>> +static void connect_sco(struct ofono_emulator *em)
>>> +{
>>> +    int err;
>>> +
>>> +    DBG("");
>>> +
>>> +    em->delay_sco = 0;
>>
>> What does this do?
>>
>>> +
>>> +    err = ofono_handsfree_card_connect_sco(em->card);
>>
>> ofono_handsfree_card_connect_sco function does not check for em->card
>> being NULL.
>>
>>> +    if (err == 0) {
>>> +        finish_codec_negotiation(em, 0);
>>> +        return;
>>> +    }
>>> +
>>> +    /* If we have another codec we can try then lets do that */
>>> +    if (em->negotiated_codec != HFP_CODEC_CVSD) {
>>> +        ofono_emulator_start_codec_negotiation(em, HFP_CODEC_CVSD,
>>> +                            em->codec_negotiation_cb,
>>> +                            em->codec_negotiation_data);
>>
>> Over 80 characters here again.  Indent less if you need to.
>>
>> ofono_handsfree_card_connect_sco won't really fail unless the kernel is
>> not configured properly.  I'm unsure of the practical utility of this
>> logic.  Would it be simpler to mark the wideband / negotiated codec as
>> unsupported and simply error out here?
>
> This is the fallback to the mandatory codec. According to the spec this
> one must be supported by both sides so if we have selected a different
> one before we fallback to what must work but negotiate that first before
> actually using it. Sure, if we end up here then something in our system
> is wrong as when we say we support a codec we should be able to use it
> without further problems. We can go and drop this if you think we don't
> need it.

The spec says:
"If an (e)SCO link cannot be established according to the parameters 
required for the selected codec (e.g., basebands negotiation fails for a 
link with re-transmission although a wide band codec has been selected), 
the Codec Connection establishment procedure shall be re-started by the 
AG with the purpose of selecting a codec that can be used. The mandatory 
narrow band Codec (CVSD) shall be used before the AG gives up trying to 
establish a Codec connection."

In practice, the only failure we can detect here is if setsockopt for 
BT_VOICE fails inside apply_codec_settings.  But I'm okay keeping this 
logic...

Regards,
-Denis