From b66ed232383162dc52d6a1c996599541860d1f1a Mon Sep 17 00:00:00 2001 From: Roman Penyaev Date: Thu, 23 Jan 2025 09:53:22 +0100 Subject: chardev/char-hub: implement backend chardev aggregator MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: "Marc-André Lureau" Cc: qemu-devel@nongnu.org Message-ID: <20250123085327.965501-3-r.peniaev@gmail.com> --- chardev/chardev-internal.h | 51 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 50 insertions(+), 1 deletion(-) (limited to 'chardev/chardev-internal.h') diff --git a/chardev/chardev-internal.h b/chardev/chardev-internal.h index 853807f..9752dd7 100644 --- a/chardev/chardev-internal.h +++ b/chardev/chardev-internal.h @@ -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); -- cgit v1.1