QEMU's screendump command can only take dumps from the primary display.
When using multiple VGA cards, there is no way to get a dump from a
secondary card or other display heads yet. So let's add an 'device' and
a 'head' parameter to the HMP and QMP commands to be able to specify
alternative devices and heads with the screendump command, too.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 v3:
 - Drop redundant qemu_console_lookup_by_index(0);
 - Remove trailing "." from error message

 hmp-commands.hx |  7 ++++---
 hmp.c           |  4 +++-
 qapi/ui.json    |  7 ++++++-
 ui/console.c    | 24 +++++++++++++++++++-----
 4 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index d26eb41..ebb5fe4 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -253,9 +253,10 @@ ETEXI
 
     {
         .name       = "screendump",
-        .args_type  = "filename:F",
-        .params     = "filename",
-        .help       = "save screen into PPM image 'filename'",
+        .args_type  = "filename:F,device:s?,head:i?",
+        .params     = "filename [device [head]]",
+        .help       = "save screen from head 'head' of display device 'device' "
+                      "into PPM image 'filename'",
         .cmd        = hmp_screendump,
     },
 
diff --git a/hmp.c b/hmp.c
index ae86bfb..7dcf72f 100644
--- a/hmp.c
+++ b/hmp.c
@@ -2132,9 +2132,11 @@ err_out:
 void hmp_screendump(Monitor *mon, const QDict *qdict)
 {
     const char *filename = qdict_get_str(qdict, "filename");
+    const char *id = qdict_get_try_str(qdict, "device");
+    int64_t head = qdict_get_try_int(qdict, "head", 0);
     Error *err = NULL;
 
-    qmp_screendump(filename, &err);
+    qmp_screendump(filename, id != NULL, id, id != NULL, head, &err);
     hmp_handle_error(mon, &err);
 }
 
diff --git a/qapi/ui.json b/qapi/ui.json
index 3e82f25..e60b323 100644
--- a/qapi/ui.json
+++ b/qapi/ui.json
@@ -77,6 +77,10 @@
 #
 # @filename: the path of a new PPM file to store the image
 #
+# @device: ID of the display device that should be used (since 2.12)
+#
+# @head: head to use in case the device supports multiple heads (since 2.12)
+#
 # Returns: Nothing on success
 #
 # Since: 0.14.0
@@ -88,7 +92,8 @@
 # <- { "return": {} }
 #
 ##
-{ 'command': 'screendump', 'data': {'filename': 'str'} }
+{ 'command': 'screendump',
+  'data': {'filename': 'str', '*device': 'str', '*head': 'int'} }
 
 ##
 # == Spice
diff --git a/ui/console.c b/ui/console.c
index e22931a..4e4296d 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -344,14 +344,28 @@ write_err:
     goto out;
 }
 
-void qmp_screendump(const char *filename, Error **errp)
+void qmp_screendump(const char *filename, bool has_device, const char *device,
+                    bool has_head, int64_t head, Error **errp)
 {
-    QemuConsole *con = qemu_console_lookup_by_index(0);
+    QemuConsole *con;
     DisplaySurface *surface;
 
-    if (con == NULL) {
-        error_setg(errp, "There is no QemuConsole I can screendump from.");
-        return;
+    if (has_device) {
+        con = qemu_console_lookup_by_device_name(device, has_head ? head : 0,
+                                                 errp);
+        if (!con) {
+            return;
+        }
+    } else {
+        if (has_head) {
+            error_setg(errp, "'head' must be specified together with 'device'");
+            return;
+        }
+        con = qemu_console_lookup_by_index(0);
+        if (!con) {
+            error_setg(errp, "There is no console to take a screendump from");
+            return;
+        }
     }
 
     graphic_hw_update(con);
-- 
1.8.3.1

On Mon, Mar 05, 2018 at 12:08:25PM +0100, Thomas Huth wrote:
> QEMU's screendump command can only take dumps from the primary display.
> When using multiple VGA cards, there is no way to get a dump from a
> secondary card or other display heads yet. So let's add an 'device' and
> a 'head' parameter to the HMP and QMP commands to be able to specify
> alternative devices and heads with the screendump command, too.
> 
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

cheers,
  Gerd

PS: With an ack from qom folks I can take this through the ui patch
    queue, alternatively feel free to put this into the qom queue.

On 03/05/2018 05:08 AM, Thomas Huth wrote:

In the subject line: s/whith/with/

Also, it's rather long (over 75 characters, while typical messages are 
under 65, since it is nice to still fit in 80 columns even when 'git 
log' adds indentation), better might be:

qapi: Add parameters to screendump

then go into details about the parameters in the commit body

> QEMU's screendump command can only take dumps from the primary display.
> When using multiple VGA cards, there is no way to get a dump from a
> secondary card or other display heads yet. So let's add an 'device' and
> a 'head' parameter to the HMP and QMP commands to be able to specify
> alternative devices and heads with the screendump command, too.
> 
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   v3:
>   - Drop redundant qemu_console_lookup_by_index(0);
>   - Remove trailing "." from error message
> 

> +++ b/qapi/ui.json
> @@ -77,6 +77,10 @@
>   #
>   # @filename: the path of a new PPM file to store the image
>   #
> +# @device: ID of the display device that should be used (since 2.12)

Worth mentioning how the default value is computed?

> +#
> +# @head: head to use in case the device supports multiple heads (since 2.12)
> +#
>   # Returns: Nothing on success
>   #
>   # Since: 0.14.0
> @@ -88,7 +92,8 @@
>   # <- { "return": {} }
>   #
>   ##
> -{ 'command': 'screendump', 'data': {'filename': 'str'} }
> +{ 'command': 'screendump',
> +  'data': {'filename': 'str', '*device': 'str', '*head': 'int'} }
>   

QAPI changes are reasonable from a UI point of view.

> +    } else {
> +        if (has_head) {
> +            error_setg(errp, "'head' must be specified together with 'device'");

This isn't documented.

> +            return;
> +        }
> +        con = qemu_console_lookup_by_index(0);
> +        if (!con) {
> +            error_setg(errp, "There is no console to take a screendump from");
> +            return;
> +        }
>       }
>   
>       graphic_hw_update(con);
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org