Re: [Qemu-devel] [PATCH v2 03/15] char-pty: Drop "char device redirected to" message

[Markus Armbruster <armbru@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 11/04/19 16:52, Markus Armbruster wrote:
>> char_pty_open() prints a "char device redirected to PTY_NAME (label
>> LABEL)" message to the current monitor or else to stderr.  No other
>> ChardevClass::open() prints anything on success.  Drop the message.
>> 
>> Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>> ---
>>  chardev/char-pty.c | 2 --
>>  1 file changed, 2 deletions(-)
>> 
>> diff --git a/chardev/char-pty.c b/chardev/char-pty.c
>> index b034332edd..a48d3e5d20 100644
>> --- a/chardev/char-pty.c
>> +++ b/chardev/char-pty.c
>> @@ -211,8 +211,6 @@ static void char_pty_open(Chardev *chr,
>>      qemu_set_nonblock(master_fd);
>>  
>>      chr->filename = g_strdup_printf("pty:%s", pty_name);
>> -    error_printf("char device redirected to %s (label %s)\n",
>> -                 pty_name, chr->label);
>>  
>>      s = PTY_CHARDEV(chr);
>>      s->ioc = QIO_CHANNEL(qio_channel_file_new_fd(master_fd));
>
> The reason for the message is that the char device is completely useless
> until the user knows the /dev/pts/N path[1].  You can get it with "info
> chardev" (aka query-chardev for QMP) but there's an interesting chicken
> and egg problem if the pty is for your monitor...
>
> Paolo

During review of v1, I wrote:

    If we should decide the message is still useful enough to be worth
    keeping, I could direct it to stdout instead of dropping it.

No clear conclusion emerged, so I did nothing for v2.  If we conclude to
keep the message now, I'll gladly do that.

> [1] once you know it, you can use the monitor's readline interface with
> e.g. "socat STDIO,cfmakeraw FILE:/dev/pts/1"

There's also

    $ socat UNIX:/path/to/socket READLINE,history=$HOME/.hmp_history,prompt='(qemu) '

Lacks completion.  But then our very own reimplementation of readline
lacks any number of other features.