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Date: Fri, 31 May 2013 14:45:29 +0200
From: Peter Krempa <pkrempa@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] chardev: fix "info chardev" output
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To: Eric Blake <eblake@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, stefano.stabellini@eu.citrix.com, Gerd Hoffmann <kraxel@redhat.com>, qemu-devel@nongnu.org

On 05/31/13 14:36, Eric Blake wrote:
> On 05/28/2013 12:34 AM, Gerd Hoffmann wrote:
>> Fill unset CharDriverState->filename with the backend name, so
>> 'info chardev' will return at least the chardev type.  Don't
>> touch it in case the chardev init function filled it already,
>> like the socket+pty chardevs do for example.
>>
>> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>> ---
>>   qemu-char.c |    3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/qemu-char.c b/qemu-char.c
>> index f825294..d04b429 100644
>> --- a/qemu-char.c
>> +++ b/qemu-char.c
>> @@ -3801,6 +3801,9 @@ ChardevReturn *qmp_chardev_add(const char *id, ChardevBackend *backend,
>>           chr->label = g_strdup(id);
>>           chr->avail_connections =
>>               (backend->kind == CHARDEV_BACKEND_KIND_MUX) ? MAX_MUX : 1;
>> +        if (!chr->filename) {
>> +            chr->filename = g_strdup(ChardevBackendKind_lookup[backend->kind]);
>> +        }
>>           QTAILQ_INSERT_TAIL(&chardevs, chr, next);
>>           return ret;
>>       } else {
>>
> 
> Peter was telling me on IRC that this patch is still broken with regards
> to libvirt; I've cc'd him to provide more details...
> 

Without this patch the returned message for "query-chardev" is:

{
    "return": [
        {
            "filename": "pty:/dev/pts/8",
            "label": "charserial0"
        },
        {
            "filename": "unix:/var/lib/libvirt/qemu/qemu-git.monitor,server",
            "label": "charmonitor"
        }
    ],
    "id": "libvirt-2"
}


this patch changes it to:

{
    "return": [
        {
            "filename": "pty",
            "label": "charserial0"
        },
        {
            "filename": "unix:/var/lib/libvirt/qemu/qemu-git.monitor,server",
            "label": "charmonitor"
        }
    ],
    "id": "libvirt-2"
}

It's apparent that some code being executed after the code in this patch
fills the actual pty path that was allocated. With it pre-allocated the
code ignores it. Libvirt is using the output to gather names of the pty
so that they can be used to connect to the console.

Peter