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From:   Adam Pigg <adam@piggz.co.uk>
Date:   Mon, 1 Aug 2022 17:33:48 +0100
Message-ID: <CANFkB1wRz9Rmh32UqCHtzinSyWNy4-6Un4cxZbtJya6brNt9Pw@mail.gmail.com>
Subject: Re: GattCharacteristic1 WriteValue fails parameter validation in a
 GATT Client
To:     John Klug <John.Klug@multitech.com>
Cc:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        Linux-Bluetooth MailingList <linux-bluetooth@vger.kernel.org>
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On Mon, 1 Aug 2022 at 17:11, John Klug <John.Klug@multitech.com> wrote:
>
> Luiz Augusto von Dentz writes:
>
> >You can use AcquireWrite and then write directly to the fd received.
>
> I tried AcquireWrite as you suggest.  The result was "NotSupported".  I
> should mention that I have tried Nordic's NRF Connect on Android with
> the same GATT Server, and it is able to write to this
> UUID/characteristic just fine.
>
>
> Using "dbus-monitor --system" I see both read and write flags on my characteristic "service0021/char0046" with the correct UUID:
>
>
> signal time=1659368288.691466 sender=:1.3649 -> destination=(null
> destination) serial=968 path=/;
> interface=org.freedesktop.DBus.ObjectManager; member=InterfacesAdded
>
>    object path "/org/bluez/hci0/dev_CC_F9_57_89_8B_D8/service0021/char0046"
>    array [
>       dict entry(
>          string "org.freedesktop.DBus.Introspectable"
>          array [
>          ]
>       )
>       dict entry(
>          string "org.bluez.GattCharacteristic1"
>          array [
>             dict entry(
>                string "UUID"
>                variant                   string "edf50100-681e-4b92-999c-e16b3a8bc047"
>             )
>             dict entry(
>                string "Service"
>                variant                   object path "/org/bluez/hci0/dev_CC_F9_57_89_8B_D8/service0021"
>             )
>             dict entry(
>                string "Value"
>                variant                   array [
>                   ]
>             )
>             dict entry(
>                string "Flags"
>                variant                   array [
>                      string "read"
>                      string "write"
>                   ]
>             )
>          ]
>       )
>       dict entry(
>          string "org.freedesktop.DBus.Properties"
>          array [
>          ]
>       )
>    ]
>
>
>
> However, AcquireWrite replies with "Not Supported" which is the text I see in the error message in my program:
>
>
> method call time=1659368290.693590 sender=:1.3987 ->
> destination=org.bluez serial=10
> path=/org/bluez/hci0/dev_CC_F9_57_89_8B_D8/service0021/char0046;
> interface=org.bluez.GattCharacteristic1; member=AcquireWrite
>
>    array [
>    ]
> error time=1659368290.693700 sender=:1.3649 -> destination=:1.3987 error_name=org.bluez.Error.NotSupported reply_serial=10
>    string "Operation is not supported"
>
> Any ideas on where in the BlueZ source I could look for this?  Does anyone have an example of doing a GATT Write from a client?

I have a watch companion application called Amazfish which does a lot
of writing using the DBUS api.  I wrote a simple Qt style wrapper
around the dbus part which is at https://github.com/piggz/qble , and
the app is at https://github.com/piggz/harbour-amazfish . Perhaps
something in there will help you.

Adam
>
>
>
> John Klug