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From:   Alain Michaud <alainmichaud@google.com>
Date:   Tue, 28 Jul 2020 09:10:39 -0400
Message-ID: <CALWDO_Wo23ev9DcpvUoDdfWQYqVRcSXp-mMysRgzpcC8auf3gQ@mail.gmail.com>
Subject: Re: [Bluez PATCH] main: adding configurable eir_max_name_len
To:     Marcel Holtmann <marcel@holtmann.org>
Cc:     Alain Michaud <alainm@chromium.org>,
        linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        Sonny Sasaka <sonnysasaka@chromium.org>
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On Tue, Jul 28, 2020 at 2:58 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Alain,
>
> > This change adds support for a configurable eir_max_name_len for
> > platforms which requires a larger than 48 bytes complete name in EIR.
> >
> > From bluetoothctl:
> > [bluetooth]# system-alias
> > 012345678901234567890123456789012345678901234567890123456789
> > Changing 012345678901234567890123456789012345678901234567890123456789
> > succeeded
> > [CHG] Controller DC:71:96:69:02:89 Alias:
> > 012345678901234567890123456789012345678901234567890123456789
> >
> > From btmon:
> > < HCI Command: Write Local Name (0x03|0x0013) plen 248             #109
> > [hci0] 88.567990
> >         Name:
> > 012345678901234567890123456789012345678901234567890123456789
> >> HCI Event: Command Complete (0x0e) plen 4
> >    #110 [hci0] 88.663854
> >       Write Local Name (0x03|0x0013) ncmd 1
> >         Status: Success (0x00)
> > @ MGMT Event: Local Name Changed (0x0008) plen 260
> > {0x0004} [hci0] 88.663948
> >         Name:
> > 012345678901234567890123456789012345678901234567890123456789
> >         Short name:
> > < HCI Command: Write Extended Inquiry Response (0x03|0x0052) plen 241
> >         FEC: Not required (0x00)
> >         Name (complete):
> > 012345678901234567890123456789012345678901234567890123456789
> >         TX power: 12 dBm
> >         Device ID: Bluetooth SIG assigned (0x0001)
> >           Vendor: Google (224)
> >           Product: 0xc405
> >           Version: 0.5.6 (0x0056)
> >         16-bit Service UUIDs (complete): 7 entries
> >           Generic Access Profile (0x1800)
> >           Generic Attribute Profile (0x1801)
> >           Device Information (0x180a)
> >           A/V Remote Control (0x110e)
> >           A/V Remote Control Target (0x110c)
> >           Handsfree Audio Gateway (0x111f)
> >           Audio Source (0x110a)
> >> HCI Event: Command Complete (0x0e) plen 4
> >       Write Extended Inquiry Response (0x03|0x0052) ncmd 1
> >         Status: Success (0x00)
> >
> > Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
> > Signed-off-by: Alain Michaud <alainm@chromium.org>
> > ---
> >
> > doc/mgmt-api.txt |  1 +
> > src/adapter.c    | 10 +++++++++-
> > src/hcid.h       |  1 +
> > src/main.c       |  5 +++++
> > src/main.conf    |  5 +++++
> > 5 files changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/doc/mgmt-api.txt b/doc/mgmt-api.txt
> > index ca0d38469..1bc0f0c12 100644
> > --- a/doc/mgmt-api.txt
> > +++ b/doc/mgmt-api.txt
> > @@ -3279,6 +3279,7 @@ Read Default System Configuration Command
> >               0x0019  LE Connection Latency
> >               0x001a  LE Connection Supervision Timeout
> >               0x001b  LE Autoconnect Timeout
> > +             0x001c  Max EIR Name Length
>
> we can certainly do this, but I prefer that do this for LE and BR/EDR and name it that way as well.
I do think that we need distinct values for br/edr and le since the
available space is different.  I don't think a single value makes
sense for both transports.

>
> >
> >       This command can be used at any time and will return a list of
> >       supported default parameters as well as their current value.
> > diff --git a/src/adapter.c b/src/adapter.c
> > index 5e896a9f0..3adc67b63 100644
> > --- a/src/adapter.c
> > +++ b/src/adapter.c
> > @@ -2375,7 +2375,7 @@ static bool parse_pathloss(DBusMessageIter *value,
> >       return true;
> > }
> >
> > -static bool parse_transport(DBusMessageIter *value,
> > +static bool parse_transport(DBusMessageIter *value,
> >                                       struct discovery_filter *filter)
> > {
> >       char *transport_str;
> > @@ -4435,6 +4435,14 @@ static void load_default_system_params(struct btd_adapter *adapter)
> >               len += sizeof(params[i].u16);
> >       }
> >
> > +     if (main_opts.default_params.eir_max_name_len) {
> > +             params[i].entry.type = 0x001c;
> > +             params[i].entry.length = sizeof(params[i].u16);
> > +             params[i].u16 = main_opts.default_params.eir_max_name_len;
> > +             ++i;
> > +             len += sizeof(params[i].u16);
> > +     }
> > +
>
> Do you really want to keep it as uint16_t or is that just laziness since changing the kernel to support anything other than uint16_t is complicated?
Yes, this is to re-use the existing infra without complicating the
buffer structure.  There are a couple more values that are effectively
uint8_t but use uint16_t above (like page scan type).

>
> On a side note, you need to provide a uint16_t value in little endian to the MGMT wire protocol.
Sounds like this is a separate issue that needs to be fixed for all
values then.  I'd rather keep that as a separate patch.

>
> >       err = mgmt_send(adapter->mgmt, MGMT_OP_SET_DEF_SYSTEM_CONFIG,
> >                       adapter->dev_id, len, params, NULL, NULL, NULL);
> >       if (!err)
> > diff --git a/src/hcid.h b/src/hcid.h
> > index 5f249ebf9..c9b59a374 100644
> > --- a/src/hcid.h
> > +++ b/src/hcid.h
> > @@ -93,6 +93,7 @@ struct main_opts {
> >               uint16_t        le_conn_latency;
> >               uint16_t        le_conn_lsto;
> >               uint16_t        le_autoconnect_timeout;
> > +             uint16_t        eir_max_name_len;
> >       } default_params;
> >
> >
> > diff --git a/src/main.c b/src/main.c
> > index ec7a9fbd7..74876e01d 100644
> > --- a/src/main.c
> > +++ b/src/main.c
> > @@ -123,6 +123,7 @@ static const char *controller_options[] = {
> >       "LEConnectionLatency",
> >       "LEConnectionSupervisionTimeout",
> >       "LEAutoconnecttimeout",
> > +     "EirMaxNameLength",
> >       NULL
> > };
> >
> > @@ -433,6 +434,10 @@ static void parse_controller_config(GKeyFile *config)
> >                 &main_opts.default_params.le_autoconnect_timeout,
> >                 0x0001,
> >                 0x4000},
> > +             { "EirMaxNameLength",
> > +               &main_opts.default_params.eir_max_name_len,
> > +               0x0001,
> > +               0x00EE},
> >       };
> >       uint16_t i;
> >
> > diff --git a/src/main.conf b/src/main.conf
> > index f41203b96..7ecac5930 100644
> > --- a/src/main.conf
> > +++ b/src/main.conf
> > @@ -148,6 +148,11 @@
> > #LEConnectionSupervisionTimeout=
> > #LEAutoconnecttimeout=
> >
> > +# EIR Max Name. This is the maximum length for the COMPLETE_NAME EIR section.
> > +# If the name length exceeds this size, a SHORT_NAME section is used.
> > +# Default: 48
> > +#EirMaxNameLength = 48
> > +
> > [GATT]
> > # GATT attribute cache.
> > # Possible values:
>
> Regards
>
> Marcel
>