On Tue, Jul 26, 2022 at 12:32:32PM +0400, marcandre.lureau@xxxxxxxxxx wrote: > From: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx> > > As Ed Swierk explained back in 2006: > https://lists.nongnu.org/archive/html/qemu-devel/2006-12/msg00160.html > > "When qemu writes into the pipe, it immediately reads back what it just > wrote and treats it as a monitor command, endlessly breathing its own > exhaust." > > This is similarly confusing when using the chardev with a serial device, > as reported in https://bugzilla.redhat.com/show_bug.cgi?id=2106975. > > It seems we have kept the support for bidirectional pipes for historical > reasons and odd systems, however it's not documented in qemu -chardev > options. I suggest to stop supporting it, for portability reasons. Hmm, I always assumed that in this scenario the pipe was operating in output-only mode. Obviously not the case with the code as it exists, but perhaps this would be useful ? eg its good as a serial console logging mechanism at least. > > Signed-off-by: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx> > --- > docs/about/deprecated.rst | 6 ++++++ > chardev/char-pipe.c | 4 ++++ > 2 files changed, 10 insertions(+) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index 7ee26626d5cf..dd5ca30d527b 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -45,6 +45,12 @@ transmit audio through the VNC protocol. > ``tty`` and ``parport`` are aliases that will be removed. Instead, the > actual backend names ``serial`` and ``parallel`` should be used. > > +``-chardev pipe`` support for bidirectional pipes (since 7.1) > +'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' > + > +For portability reasons, the support for bidirectional ``pipe`` will > +be removed. Instead, use ``file.in`` & ``file.out`` unidirectional pipes. > + > Short-form boolean options (since 6.0) > '''''''''''''''''''''''''''''''''''''' > > diff --git a/chardev/char-pipe.c b/chardev/char-pipe.c > index 66d3b8509183..7db963035e7d 100644 > --- a/chardev/char-pipe.c > +++ b/chardev/char-pipe.c > @@ -27,6 +27,7 @@ > #include "qemu/main-loop.h" > #include "qemu/module.h" > #include "qemu/option.h" > +#include "qemu/error-report.h" > #include "chardev/char.h" > > #ifdef _WIN32 > @@ -142,6 +143,9 @@ static void qemu_chr_open_pipe(Chardev *chr, > if (fd_out >= 0) { > close(fd_out); > } > + warn_report("Support for bidirectional pipe is deprecated,"); > + warn_report("please use portable one-way pipes instead (%s.in & %s.out).", > + filename, filename); > TFR(fd_in = fd_out = qemu_open_old(filename, O_RDWR | O_BINARY)); > if (fd_in < 0) { > error_setg_file_open(errp, errno, filename); > -- > 2.37.0.rc0 > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
