It has been unmaintained since years, and there were only trivial or
tree-wide changes to the related files since many years, so the
code is likely very bitrotten and broken. For example the following
segfaults as soon as as you press a key:

 qemu-system-x86_64 -usb -device usb-bt-dongle -bt hci -bt device:keyboard

Since we are not aware of anybody using bluetooth with the current
version of QEMU, let's mark the subsystem as deprecated, with a special
request for the users to write to the qemu-devel mailing list in case
they still use it (so we could revert the deprecation status in that
case).

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 qemu-deprecated.texi | 7 +++++++
 qemu-options.hx      | 4 ++++
 vl.c                 | 4 ++++
 3 files changed, 15 insertions(+)

diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 5d2d7a3..cb4291f 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -128,6 +128,13 @@ The @option{[hub_id name]} parameter tuple of the 'hostfwd_add' and
 The ``ivshmem'' device type is replaced by either the ``ivshmem-plain''
 or ``ivshmem-doorbell`` device types.
 
+@subsection bluetooth (since 3.1)
+
+The bluetooth subsystem is unmaintained since many years and likely bitrotten
+quite a bit. It will be removed without replacement unless some users speaks
+up at the @email{qemu-devel@@nongnu.org} mailing list with information about
+their usecases.
+
 @section System emulator machines
 
 @subsection pc-0.10 and pc-0.11 (since 3.0)
diff --git a/qemu-options.hx b/qemu-options.hx
index 38c7a97..ee379b3 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2772,6 +2772,10 @@ logic.  The Transport Layer is decided by the machine type.  Currently
 the machines @code{n800} and @code{n810} have one HCI and all other
 machines have none.
 
+Note: This option and the whole bluetooth subsystem is considered as deprecated.
+If you still use it, please send a mail to @email{qemu-devel@@nongnu.org} where
+you describe your usecase.
+
 @anchor{bt-hcis}
 The following three types are recognized:
 
diff --git a/vl.c b/vl.c
index 55bab00..fa25d1a 100644
--- a/vl.c
+++ b/vl.c
@@ -3269,6 +3269,10 @@ int main(int argc, char **argv, char **envp)
                 break;
 #endif
             case QEMU_OPTION_bt:
+                warn_report("The bluetooth subsystem is deprecated and will "
+                            "be removed soon. If the bluetooth subsystem is "
+                            "still useful for you, please send a mail to "
+                            "qemu-devel@nongnu.org with your usecase.");
                 add_device_config(DEV_BT, optarg);
                 break;
             case QEMU_OPTION_audio_help:
-- 
1.8.3.1

On Mon, Nov 12, 2018 at 11:00:30 +0100, Thomas Huth wrote:
> It has been unmaintained since years, and there were only trivial or
> tree-wide changes to the related files since many years, so the
> code is likely very bitrotten and broken. For example the following
> segfaults as soon as as you press a key:
> 
>  qemu-system-x86_64 -usb -device usb-bt-dongle -bt hci -bt device:keyboard
> 
> Since we are not aware of anybody using bluetooth with the current
> version of QEMU, let's mark the subsystem as deprecated, with a special
> request for the users to write to the qemu-devel mailing list in case
> they still use it (so we could revert the deprecation status in that
> case).
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  qemu-deprecated.texi | 7 +++++++
>  qemu-options.hx      | 4 ++++
>  vl.c                 | 4 ++++
>  3 files changed, 15 insertions(+)

libvirt never implemented any configuration option for bluetooth

On Mon, Nov 12, 2018 at 11:00:30AM +0100, Thomas Huth wrote:
> It has been unmaintained since years, and there were only trivial or
> tree-wide changes to the related files since many years, so the
> code is likely very bitrotten and broken. For example the following
> segfaults as soon as as you press a key:
> 
>  qemu-system-x86_64 -usb -device usb-bt-dongle -bt hci -bt device:keyboard
> 
> Since we are not aware of anybody using bluetooth with the current
> version of QEMU, let's mark the subsystem as deprecated, with a special
> request for the users to write to the qemu-devel mailing list in case
> they still use it (so we could revert the deprecation status in that
> case).

I think that settles the bluetooth debate for now.  We deprecate it,
wait for feedback, possibly un-deprecate (parts of) the code.  Next
year we'll actually remove the unused code.

Patch queued for 3.1.

thanks,
  Gerd

On Mon, Nov 12, 2018 at 02:14:02PM +0100, Gerd Hoffmann wrote:
> On Mon, Nov 12, 2018 at 11:00:30AM +0100, Thomas Huth wrote:
> > It has been unmaintained since years, and there were only trivial or
> > tree-wide changes to the related files since many years, so the
> > code is likely very bitrotten and broken. For example the following
> > segfaults as soon as as you press a key:
> > 
> >  qemu-system-x86_64 -usb -device usb-bt-dongle -bt hci -bt device:keyboard
> > 
> > Since we are not aware of anybody using bluetooth with the current
> > version of QEMU, let's mark the subsystem as deprecated, with a special
> > request for the users to write to the qemu-devel mailing list in case
> > they still use it (so we could revert the deprecation status in that
> > case).
> 
> I think that settles the bluetooth debate for now.  We deprecate it,
> wait for feedback, possibly un-deprecate (parts of) the code.  Next
> year we'll actually remove the unused code.
> 
> Patch queued for 3.1.

FWIW, libvirt has never exposed any of the bluetooth functionality, so
no objections to removing it from our side.


Regards,
Daniel
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