[v6] virtio-console: notify about the terminal size

[PATCH v6 07/12] qmp: add chardev-window-size-changed command

Posted by Filip Hejsek 2 weeks, 6 days ago

From: Szymon Lukasz <noh4hss@gmail.com>

The managment software can use this command to notify QEMU about the
size of the terminal connected to a chardev, QEMU can then forward this
information to the guest if the chardev is connected to a virtio console
device.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
[Filip: rename command, change documentation]
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 chardev/char.c | 14 ++++++++++++++
 qapi/char.json | 31 +++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/chardev/char.c b/chardev/char.c
index f3c6a12c99..458059a9e0 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -1266,6 +1266,20 @@ bool qmp_add_client_char(int fd, bool has_skipauth, bool skipauth,
     return true;
 }
 
+void qmp_chardev_window_size_changed(const char *id, uint16_t cols,
+                                     uint16_t rows, Error **errp)
+{
+    Chardev *chr;
+
+    chr = qemu_chr_find(id);
+    if (chr == NULL) {
+        error_setg(errp, "Chardev '%s' not found", id);
+        return;
+    }
+
+    qemu_chr_resize(chr, cols, rows);
+}
+
 /*
  * Add a timeout callback for the chardev (in milliseconds), return
  * the GSource object created. Please use this to add timeout hook for
diff --git a/qapi/char.json b/qapi/char.json
index 140614f82c..bc08f0161a 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -861,6 +861,37 @@
 { 'command': 'chardev-send-break',
   'data': { 'id': 'str' } }
 
+##
+# @chardev-window-size-changed:
+#
+# Notifies a chardev about the current size of the terminal connected
+# to this chardev.  The information will be forwarded to the guest if
+# the chardev is connected to a virtio console device.
+#
+# The initial size is 0x0, which should be interpreted as an unknown
+# size.
+#
+# Some backends detect the terminal size automatically, in which case
+# the size may unpredictably revert to the detected one at any time.
+#
+# @id: the chardev's ID, must exist
+#
+# @cols: the number of columns
+#
+# @rows: the number of rows
+#
+# Since: 11.0
+#
+# .. qmp-example::
+#
+#     -> { "execute": "chardev-window-size-changed", "arguments": { "id": "foo", "cols": 80, "rows": 24 } }
+#     <- { "return": {} }
+##
+{ 'command': 'chardev-window-size-changed',
+  'data': { 'id': 'str',
+            'cols': 'uint16',
+            'rows': 'uint16' } }
+
 ##
 # @VSERPORT_CHANGE:
 #

-- 
2.52.0

Re: [PATCH v6 07/12] qmp: add chardev-window-size-changed command

Posted by Markus Armbruster 2 weeks, 6 days ago

Filip Hejsek <filip.hejsek@gmail.com> writes:

> From: Szymon Lukasz <noh4hss@gmail.com>
>
> The managment software can use this command to notify QEMU about the
> size of the terminal connected to a chardev, QEMU can then forward this
> information to the guest if the chardev is connected to a virtio console
> device.
>
> Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
> Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
> [Filip: rename command, change documentation]
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Acked-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>

[...]

> diff --git a/qapi/char.json b/qapi/char.json
> index 140614f82c..bc08f0161a 100644
> --- a/qapi/char.json
> +++ b/qapi/char.json
> @@ -861,6 +861,37 @@
>  { 'command': 'chardev-send-break',
>    'data': { 'id': 'str' } }
>  
> +##
> +# @chardev-window-size-changed:
> +#
> +# Notifies a chardev about the current size of the terminal connected
> +# to this chardev.  The information will be forwarded to the guest if
> +# the chardev is connected to a virtio console device.
> +#
> +# The initial size is 0x0, which should be interpreted as an unknown
> +# size.
> +#
> +# Some backends detect the terminal size automatically, in which case
> +# the size may unpredictably revert to the detected one at any time.
> +#
> +# @id: the chardev's ID, must exist

Please drop ", must exist" for consistency with ID descriptions
elsewhere.

> +#
> +# @cols: the number of columns
> +#
> +# @rows: the number of rows
> +#
> +# Since: 11.0
> +#
> +# .. qmp-example::
> +#
> +#     -> { "execute": "chardev-window-size-changed", "arguments": { "id": "foo", "cols": 80, "rows": 24 } }
> +#     <- { "return": {} }
> +##
> +{ 'command': 'chardev-window-size-changed',
> +  'data': { 'id': 'str',
> +            'cols': 'uint16',
> +            'rows': 'uint16' } }
> +
>  ##
>  # @VSERPORT_CHANGE:
>  #

Re: [PATCH v6 07/12] qmp: add chardev-window-size-changed command

Posted by Filip Hejsek 2 weeks, 5 days ago

On Mon, 2026-01-19 at 07:47 +0100, Markus Armbruster wrote:
> Filip Hejsek <filip.hejsek@gmail.com> writes:
> 
> > From: Szymon Lukasz <noh4hss@gmail.com>
> > 
> > The managment software can use this command to notify QEMU about the
> > size of the terminal connected to a chardev, QEMU can then forward this
> > information to the guest if the chardev is connected to a virtio console
> > device.
> > 
> > Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
> > Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
> > [Filip: rename command, change documentation]
> > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> > Acked-by: Markus Armbruster <armbru@redhat.com>
> > Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
> 
> [...]
> 
> > diff --git a/qapi/char.json b/qapi/char.json
> > index 140614f82c..bc08f0161a 100644
> > --- a/qapi/char.json
> > +++ b/qapi/char.json
> > @@ -861,6 +861,37 @@
> >  { 'command': 'chardev-send-break',
> >    'data': { 'id': 'str' } }
> >  
> > +##
> > +# @chardev-window-size-changed:
> > +#
> > +# Notifies a chardev about the current size of the terminal connected
> > +# to this chardev.  The information will be forwarded to the guest if
> > +# the chardev is connected to a virtio console device.
> > +#
> > +# The initial size is 0x0, which should be interpreted as an unknown
> > +# size.
> > +#
> > +# Some backends detect the terminal size automatically, in which case
> > +# the size may unpredictably revert to the detected one at any time.
> > +#
> > +# @id: the chardev's ID, must exist
> 
> Please drop ", must exist" for consistency with ID descriptions
> elsewhere.
> 

On Mon, 2025-09-22 at 11:38 +0200, Markus Armbruster wrote:
> [...]
> >> Let's drop ", must exist" for consistency with ID descriptions
> >> elsewhere.
> >
> > All chardev @id parameters in qapi/char.json have ", must exist"
> > (although you're right that nothing else has it).
> 
> Right.  Feel free to stay locally consistent then.

I'll drop it in next version, but all the other instances should be
dropped too.

> > +#
> > +# @cols: the number of columns
> > +#
> > +# @rows: the number of rows
> > +#
> > +# Since: 11.0
> > +#
> > +# .. qmp-example::
> > +#
> > +#     -> { "execute": "chardev-window-size-changed", "arguments": { "id": "foo", "cols": 80, "rows": 24 } }
> > +#     <- { "return": {} }
> > +##
> > +{ 'command': 'chardev-window-size-changed',
> > +  'data': { 'id': 'str',
> > +            'cols': 'uint16',
> > +            'rows': 'uint16' } }
> > +
> >  ##
> >  # @VSERPORT_CHANGE:
> >  #

[PATCH] qapi: drop "must exist" from ID descriptions for consistency

Posted by Filip Hejsek 2 weeks, 5 days ago

Make chardev ID param descriptions more consistend with ID descriptions
elsewhere.
---
 qapi/char.json | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/qapi/char.json b/qapi/char.json
index 140614f82c..fbac5a1cb7 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -791,7 +791,7 @@
 #
 # Change a character device backend
 #
-# @id: the chardev's ID, must exist
+# @id: the chardev's ID
 #
 # @backend: new backend type and parameters
 #
@@ -832,7 +832,7 @@
 #
 # Remove a character device backend
 #
-# @id: the chardev's ID, must exist and not be in use
+# @id: the chardev's ID, must not be in use
 #
 # Since: 1.4
 #
@@ -849,7 +849,7 @@
 #
 # Send a break to a character device
 #
-# @id: the chardev's ID, must exist
+# @id: the chardev's ID
 #
 # Since: 2.10
 #
-- 
2.52.0