Re: [Qemu-devel] [PATCH 5/5] HMP: Introduce console command

[Lei Li <lilei@linux.vnet.ibm.com>]

On 10/24/2012 08:55 PM, Luiz Capitulino wrote:
> On Wed, 24 Oct 2012 15:17:21 +0800
> Lei Li <lilei@linux.vnet.ibm.com> wrote:
>
>> On 10/23/2012 02:59 AM, Luiz Capitulino wrote:
>>> On Mon, 22 Oct 2012 00:48:01 +0800
>>> Lei Li <lilei@linux.vnet.ibm.com> wrote:
>>>
>>>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>>>> ---
>>>>    hmp-commands.hx |   23 +++++++++++++++++++++++
>>>>    hmp.c           |   53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>    hmp.h           |    1 +
>>>>    monitor.c       |   15 +++++++++++++++
>>>>    monitor.h       |    3 +++
>>>>    5 files changed, 95 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/hmp-commands.hx b/hmp-commands.hx
>>>> index 5f91428..f862a53 100644
>>>> --- a/hmp-commands.hx
>>>> +++ b/hmp-commands.hx
>>>> @@ -868,7 +868,30 @@ char device and return @var{size} of the data.
>>>>    that specifies behavior when the queue is full/empty. By default is
>>>>    'drop'. Note that the 'block' option is not supported now.
>>>>            -b for 'block' option. None for 'drop' option.
>>>> +ETEXI
>>>> +
>>>> +    {
>>>> +        .name       = "console",
>>>> +        .args_type  = "chardev:s",
>>>> +        .params     = "chardev",
>>>> +        .help       = "Connect to the serial console from within the"
>>>> +                      "monitor, allow to write data to memchardev"
>>>> +                      "'chardev'. Exit from the console and return back"
>>>> +                      "to monitor by typing 'ctrl-]'",
>>>> +        .mhandler.cmd = hmp_console,
>>>> +    },
>>>>    
>>>> +STEXI
>>>> +@item console @var{device}
>>>> +@findex console
>>>> +
>>>> +Connect to the serial console from within the monitor, allow to write data
>>>> +to memchardev @var{chardev}. Exit from the console and return back to
>>>> +monitor by typing 'ctrl-]'.
>>>> +@example
>>>> +(qemu) console foo
>>>> +foo: data string...
>>>> +@end example
>>>>    ETEXI
>>>>    
>>>>        {
>>>> diff --git a/hmp.c b/hmp.c
>>>> index fa858c4..bc245f4 100644
>>>> --- a/hmp.c
>>>> +++ b/hmp.c
>>>> @@ -1245,3 +1245,56 @@ void hmp_screen_dump(Monitor *mon, const QDict *qdict)
>>>>        qmp_screendump(filename, &err);
>>>>        hmp_handle_error(mon, &err);
>>>>    }
>>>> +
>>>> +enum escape_char
>>>> +{
>>>> +    ESCAPE_CHAR_CTRL_GS = 0x1d  /* ctrl-] used for escape */
>>>> +};
>>>> +
>>>> +static void hmp_read_console(Monitor *mon, const char *data,
>>>> +                             void *opaque)
>>>> +{
>>>> +    CharDriverState *chr = opaque;
>>>> +    uint32_t size = strlen(data);
>>>> +    enum DataFormat format = DATA_FORMAT_UTF8;
>>>> +    enum CongestionControl control = CONGESTION_CONTROL_DROP;
>>>> +    enum escape_char console_escape = ESCAPE_CHAR_CTRL_GS;
>>>> +
>>>> +    Error *err = NULL;
>>>> +
>>>> +    if (*data == console_escape) {
>>>> +        monitor_resume(mon);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    qmp_memchar_write(chr->label, size, data, 0, format,
>>>> +                      0, control, &err);
>>>> +    if (err) {
>>>> +        monitor_printf(mon, "%s\n", error_get_pretty(err));
>>>> +        error_free(err);
>>>> +        return;
>>>> +    }
>>> Shouldn't you also read from the device?
>> The use-case for this console command is just allow the user to
>> write data to each memchar device as in a signal terminal. Then
>> type escape sequences to take you back to the monitor. So I don't
>> think it is also need to read from the device in this command.
>>
>> BTW, we can read from the device by hmp_memchar_read. :)
> And how is the console command better than the hmp_memchar_write one?
>
> Could you please give examples?

Sure. The "console" command behaves like:

(qemu) console foo
foo: hello world
(qemu)

you can input data, then put enter or ctrl-] to return back to
the monitor. The data input from console would be written to the
CirMemCharDriver backend, which provide a more friendly and nice
HMP command as Anthony suggested.


>
>>>> +
>>>> +    monitor_read_command(mon, 1);
>>>> +}
>>>> +
>>>> +void hmp_console(Monitor *mon, const QDict *qdict)
>>>> +{
>>>> +    const char *device = qdict_get_str(qdict, "chardev");
>>>> +    CharDriverState *chr;
>>>> +    Error *err = NULL;
>>>> +
>>>> +    chr = qemu_chr_find(device);
>>>> +
>>>> +    if (!chr) {
>>>> +        error_set(&err, QERR_DEVICE_NOT_FOUND, device);
>>>> +        goto out;
>>>> +    }
>>> No need to do this here as the QMP command will do it too.
>>>
>> I think we should do this check here, otherwise would
>> cause core dump when 'console' to a chardev that does not
>> exist. Wepass parameterchr->label by qmp_memchar_write()
>> in the handler hmp_read_console.
> Do you need the chr object? Why don't you just pass 'device' to
> monitor_read_console()?

Yes, we need 'device' and 'chr' both here. 'device' pass to monitor_read_console
for the friendly prompt. 'chr' pass to handler hmp_read_console, the reason did not
pass 'device' directly to it is the limitation of argument for the handler
hmp_read_console. Also it's better to give the prompt before the user enter the input
console if the device not found, the use-case as I post above.

>>>> +
>>>> +    if (monitor_read_console(mon, device, hmp_read_console, chr) < 0) {
>>>> +        monitor_printf(mon, "Connect to console %s failed\n", device);
>>>> +    }
>>>> +
>>>> +out:
>>>> +    hmp_handle_error(mon, &err);
>>>> +}
>>>> diff --git a/hmp.h b/hmp.h
>>>> index a5a0cfe..5b54a79 100644
>>>> --- a/hmp.h
>>>> +++ b/hmp.h
>>>> @@ -77,5 +77,6 @@ void hmp_getfd(Monitor *mon, const QDict *qdict);
>>>>    void hmp_closefd(Monitor *mon, const QDict *qdict);
>>>>    void hmp_send_key(Monitor *mon, const QDict *qdict);
>>>>    void hmp_screen_dump(Monitor *mon, const QDict *qdict);
>>>> +void hmp_console(Monitor *mon, const QDict *qdict);
>>>>    
>>>>    #endif
>>>> diff --git a/monitor.c b/monitor.c
>>>> index 131b325..453c084 100644
>>>> --- a/monitor.c
>>>> +++ b/monitor.c
>>>> @@ -256,6 +256,21 @@ int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
>>>>        }
>>>>    }
>>>>    
>>>> +int monitor_read_console(Monitor *mon, const char *device,
>>>> +                         ReadLineFunc *readline_func, void *opaque)
>>>> +{
>>>> +    char prompt[60];
>>>> +
>>>> +    if (!mon->rs) {
>>>> +        return -1;
>>>> +    }
>>>> +
>>>> +    snprintf(prompt, sizeof(prompt), "%s: ", device);
>>>> +    readline_start(mon->rs, prompt, 0, readline_func, opaque);
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>>    void monitor_flush(Monitor *mon)
>>>>    {
>>>>        if (mon && mon->outbuf_index != 0 && !mon->mux_out) {
>>>> diff --git a/monitor.h b/monitor.h
>>>> index b6e7d95..735bd1b 100644
>>>> --- a/monitor.h
>>>> +++ b/monitor.h
>>>> @@ -86,6 +86,9 @@ ReadLineState *monitor_get_rs(Monitor *mon);
>>>>    int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
>>>>                              void *opaque);
>>>>    
>>>> +int monitor_read_console(Monitor *mon, const char *device,
>>>> +                         ReadLineFunc *readline_func, void *opaque);
>>>> +
>>>>    int qmp_qom_set(Monitor *mon, const QDict *qdict, QObject **ret);
>>>>    
>>>>    int qmp_qom_get(Monitor *mon, const QDict *qdict, QObject **ret);
>>
>


-- 
Lei