Re: [PATCH 2/3] docs/s390x: document 3270

[Thomas Huth <thuth@redhat.com>]

On 05/05/2020 15.50, Cornelia Huck wrote:
> Add some basic info how to use 3270 devices.
> 
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
>  docs/system/s390x/3270.rst   | 32 ++++++++++++++++++++++++++++++++
>  docs/system/target-s390x.rst |  1 +
>  2 files changed, 33 insertions(+)
>  create mode 100644 docs/system/s390x/3270.rst
> 
> diff --git a/docs/system/s390x/3270.rst b/docs/system/s390x/3270.rst
> new file mode 100644
> index 000000000000..e367a457e001
> --- /dev/null
> +++ b/docs/system/s390x/3270.rst
> @@ -0,0 +1,32 @@
> +3270 devices
> +============
> +
> +With the aid of the ``x3270`` emulator, QEMU provides limited support
> +for making a single 3270 device available to a guest. Note that this
> +supports basic features only.

The first sentence sounds somewhat confusing. Maybe rather something like:

QEMU can emulate a 3270 device attached to a guest, which then can be
used with a program like ``x3270`` to get a traditional 3270 terminal
for your guest.

?

> +To provide a 3270 device to a guest, create a ``x-3270device`` linked to

The device is called "x-terminal3270", isn't it?

(By the way, why did we never remove the x- prefix here? Is it still
experimental?)

> +a ``tn3270`` chardev. The guest will see a 3270 channel device. In order
> +to actually be able to use it, attach the ``x3270`` emulator to the chardev.

Can the guest only use the 3270 device if there is a x3270 attached to
it? Or are you talking about the user here?

> +Example configuration
> +---------------------
> +
> +* Add a ``tn3270`` chardev and a ``x-3270device`` to the QEMU command line::

"x-terminal3270" ?

> +    -chardev socket,id=char_0,host=0.0.0.0,port=23,nowait,server,tn3270
> +    -device x-terminal3270,chardev=char_0,devno=fe.0.000a,id=terminal_0

qemu-system-s390x: -chardev
socket,id=char_0,host=0.0.0.0,port=23,nowait,server,tn3270: Failed to
bind socket: Permission denied

... maybe better use a non-privileged port in the example?

 Thomas