motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-05 00:33:55 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

chardev/char-hub: implement backend chardev aggregator

Browse source 
This patch implements a new chardev backend `hub` device, which
aggregates input from multiple backend devices and forwards it to a
single frontend device. Additionally, `hub` device takes the output
from the frontend device and sends it back to all the connected
backend devices. This allows for seamless interaction between
different backend devices and a single frontend interface.

The idea of the change is trivial: keep list of backend devices
(up to 4), init them on demand and forward data buffer back and
forth.

The following is QEMU command line example:

   -chardev pty,path=/tmp/pty,id=pty0 \
   -chardev vc,id=vc0 \
   -chardev hub,id=hub0,chardevs.0=pty0,chardevs.1=vc0 \
   -device virtconsole,chardev=hub0 \
   -vnc 0.0.0.0:0

Which creates 2 backend devices: text virtual console (`vc0`) and a
pseudo TTY (`pty0`) connected to the single virtio hvc console with
the backend aggregator (`hub0`) help. `vc0` renders text to an image,
which can be shared over the VNC protocol.  `pty0` is a pseudo TTY
backend which provides biderectional communication to the virtio hvc
console.

'chardevs.N' list syntax is used for the sake of compatibility with
the representation of JSON lists in 'key=val' pairs format of the
util/keyval.c, despite the fact that modern QAPI way of parsing,
namely qobject_input_visitor_new_str(), is not used. Choice of keeping
QAPI list syntax may help to smoothly switch to modern parsing in the
future.

Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>
Reviewed-by: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: qemu-devel@nongnu.org
Message-ID: <20250123085327.965501-3-r.peniaev@gmail.com>
This commit is contained in:
Roman Penyaev 2025-01-23 09:53:22 +01:00 • committed by Marc-André Lureau
parent 4e059a9d96
commit b66ed23238
6 changed files with 401 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

51
chardev/chardev-internal.h
View file

@ -29,13 +29,16 @@
#include "chardev/char-fe.h"
#include "qom/object.h"
#define MAX_HUB 4
#define MAX_MUX 4
#define MUX_BUFFER_SIZE 32 /* Must be a power of 2. */
#define MUX_BUFFER_MASK (MUX_BUFFER_SIZE - 1)
struct MuxChardev {
Chardev parent;
/* Linked frontends */
CharBackend *backends[MAX_MUX];
/* Linked backend */
CharBackend chr;
unsigned long mux_bitset;
int focus;
@ -53,11 +56,57 @@ struct MuxChardev {
int64_t timestamps_start;
};
typedef struct MuxChardev MuxChardev;
typedef struct HubChardev HubChardev;
typedef struct HubCharBackend HubCharBackend;
/*
* Back-pointer on a hub, actual backend and its index in
* `hub->backends` array
*/
struct HubCharBackend {
HubChardev *hub;
CharBackend be;
unsigned int be_ind;
};
struct HubChardev {
Chardev parent;
/* Linked backends */
HubCharBackend backends[MAX_HUB];
/*
* Number of backends attached to this hub. Once attached, a
* backend can't be detached, so the counter is only increasing.
* To safely remove a backend, hub has to be removed first.
*/
unsigned int be_cnt;
/*
* Number of CHR_EVEN_OPENED events from all backends. Needed to
* send CHR_EVEN_CLOSED only when counter goes to zero.
*/
unsigned int be_event_opened_cnt;
/*
* Counters of written bytes from a single frontend device
* to multiple backend devices.
*/
unsigned int be_written[MAX_HUB];
unsigned int be_min_written;
/*
* Index of a backend device which got EAGAIN on last write,
* -1 is invalid index.
*/
int be_eagain_ind;
};
typedef struct HubChardev HubChardev;
DECLARE_INSTANCE_CHECKER(MuxChardev, MUX_CHARDEV,
TYPE_CHARDEV_MUX)
#define CHARDEV_IS_MUX(chr) \
DECLARE_INSTANCE_CHECKER(HubChardev, HUB_CHARDEV,
TYPE_CHARDEV_HUB)
#define CHARDEV_IS_MUX(chr) \
object_dynamic_cast(OBJECT(chr), TYPE_CHARDEV_MUX)
#define CHARDEV_IS_HUB(chr) \
object_dynamic_cast(OBJECT(chr), TYPE_CHARDEV_HUB)
bool mux_chr_attach_frontend(MuxChardev *d, CharBackend *b,
unsigned int *tag, Error **errp);