Re: [Qemu-devel] [PATCHv2 3/4] qxl: add debug_cs and cmdlog_cs

[Alon Levy <alevy@redhat.com>]

On Fri, Apr 29, 2011 at 02:09:54PM +0200, Gerd Hoffmann wrote:
> On 04/28/11 10:29, Alon Levy wrote:
> >With this you can output the command log and/or the guest debug (driver)
> >output to a chardev instead of stderr:
> >
> >-global qxl-vga.cmdlog_chardev=qxl_cmdlog_chardev
> >-global qxl-vga.debug_chardev=qxl_debug_chardev
> >
> >useful for debugging. if no chardev is specified prints to stderr like the old
> >code.
> 
> Hmm.  That is a bit too much ad-hoc debug hacking IMHO.  Also I'm
> not sure I like the idea to send debug stuff through chardev instead
> of just writing them to stderr or some logfile.
> 
> I do see why you are doing that though.  Unfortunaly qemu has no
> sane debug logging infrastructure.  This is long overdue IMHO, so we
> don't need hacks like this one and also don't reinvent stuff over
> and over.

The bigger hack called "qxl_terse" I didn't even send :) ok, so now I get
to either keep this in my closet or think of how to do a minimal acceptable
qemu logging infrastructure that would let me register a logging handle and
use that to redirect to a chardev (they would all default to being muxed over
stdio?)

QemuLogger *qemu_create_logger(const char *logger_id);
 - logger_id is used to match to the chardev given on the command line
 - need to prevent collision, so probably easier to have a logger_id be an int
 and have that looked up to a string in an automatically generated table?

struct QemuLogger {
  CharDriverState *chr;
};

And command line would be:
 -chardev bla,id=myid -debug qxl,myid

qxl->logger = qemu_create_logger("qxl");
qemu_chr_write(qxl->logger->chr, ..)

logger creation would have to happen before command line parsing, so in the device initialization.

Sounds right?

> 
> cheers,
>   Gerd
>