[1/1] virtio: add driver for virtio_console devices

From: "A. Cody Schuffelen" <schuffelen@google.com>

This is an implementation of single-character virtio-console. Part of the
patch is based on barebox implementations.

Signed-off-by: A. Cody Schuffelen <schuffelen@google.com>
[ Paul: pick from the Android tree. Rebase to the upstream. Small fixes. ]
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Link: https://android.googlesource.com/platform/external/u-boot/+/bc68da98ebf835a50d869cf01c535ac936bfcb11
Link: https://git.pengutronix.de/cgit/barebox/tree/drivers/serial/virtio_console.c?id=180a551d542844b70012d7b94a415aacdcf31d45
Link: https://android.googlesource.com/platform/external/u-boot/+/4581f7c6e96d7332b534ae20de356a4554594d08
Cc: Bin Meng <bmeng.cn@gmail.com>
---
 drivers/virtio/Kconfig          |   8 ++
 drivers/virtio/Makefile         |   1 +
 drivers/virtio/virtio-uclass.c  |   1 +
 drivers/virtio/virtio_console.c | 158 ++++++++++++++++++++++++++++++++
 include/virtio.h                |   2 +
 5 files changed, 170 insertions(+)
 create mode 100644 drivers/virtio/virtio_console.c

Hello,

On 06.06.23 15:25, Ying-Chun Liu (PaulLiu) wrote:
> From: "A. Cody Schuffelen" <schuffelen@google.com>
> 
> This is an implementation of single-character virtio-console. Part of the
> patch is based on barebox implementations.

Cool to see others found this useful. I had originally written this for the demo
at https://barebox.org/jsbarebox/ :-)

Back then I had trouble getting more than one console to work, whether through
multiport consoles or via having one virtio device per console. The original
barebox source code has a comment about what I tried. Did you manage to resolve
this limitation?

If not, you should add some check into your patch to prevent registering more than
one console with the driver.

Cheers,
Ahmad

> 
> Signed-off-by: A. Cody Schuffelen <schuffelen@google.com>
> [ Paul: pick from the Android tree. Rebase to the upstream. Small fixes. ]
> Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
> Link: https://android.googlesource.com/platform/external/u-boot/+/bc68da98ebf835a50d869cf01c535ac936bfcb11
> Link: https://git.pengutronix.de/cgit/barebox/tree/drivers/serial/virtio_console.c?id=180a551d542844b70012d7b94a415aacdcf31d45
> Link: https://android.googlesource.com/platform/external/u-boot/+/4581f7c6e96d7332b534ae20de356a4554594d08
> Cc: Bin Meng <bmeng.cn@gmail.com>
> ---
>  drivers/virtio/Kconfig          |   8 ++
>  drivers/virtio/Makefile         |   1 +
>  drivers/virtio/virtio-uclass.c  |   1 +
>  drivers/virtio/virtio_console.c | 158 ++++++++++++++++++++++++++++++++
>  include/virtio.h                |   2 +
>  5 files changed, 170 insertions(+)
>  create mode 100644 drivers/virtio/virtio_console.c
> 
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 852f6735b6..94aaf70ab9 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -68,6 +68,14 @@ config VIRTIO_BLK
>  	  This is the virtual block driver for virtio. It can be used with
>  	  QEMU based targets.
>  
> +config VIRTIO_CONSOLE
> +	bool "virtio console driver"
> +	depends on VIRTIO
> +	default y
> +	help
> +	  This is the virtual console driver for virtio. It can be used
> +	  with QEMU based targets.
> +
>  config VIRTIO_RNG
>  	bool "virtio rng driver"
>  	depends on DM_RNG
> diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
> index 4c63a6c690..c816f66aa6 100644
> --- a/drivers/virtio/Makefile
> +++ b/drivers/virtio/Makefile
> @@ -10,4 +10,5 @@ obj-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
>  obj-$(CONFIG_VIRTIO_SANDBOX) += virtio_sandbox.o
>  obj-$(CONFIG_VIRTIO_NET) += virtio_net.o
>  obj-$(CONFIG_VIRTIO_BLK) += virtio_blk.o
> +obj-$(CONFIG_VIRTIO_CONSOLE) += virtio_console.o
>  obj-$(CONFIG_VIRTIO_RNG) += virtio_rng.o
> diff --git a/drivers/virtio/virtio-uclass.c b/drivers/virtio/virtio-uclass.c
> index 31bb21c534..9c54c67572 100644
> --- a/drivers/virtio/virtio-uclass.c
> +++ b/drivers/virtio/virtio-uclass.c
> @@ -30,6 +30,7 @@
>  static const char *const virtio_drv_name[VIRTIO_ID_MAX_NUM] = {
>  	[VIRTIO_ID_NET]		= VIRTIO_NET_DRV_NAME,
>  	[VIRTIO_ID_BLOCK]	= VIRTIO_BLK_DRV_NAME,
> +	[VIRTIO_ID_CONSOLE]	= VIRTIO_CONSOLE_DRV_NAME,
>  	[VIRTIO_ID_RNG]		= VIRTIO_RNG_DRV_NAME,
>  };
>  
> diff --git a/drivers/virtio/virtio_console.c b/drivers/virtio/virtio_console.c
> new file mode 100644
> index 0000000000..1d4b319b08
> --- /dev/null
> +++ b/drivers/virtio/virtio_console.c
> @@ -0,0 +1,158 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2018, Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
> + * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
> + * Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
> + * Copyright (C) 2009, 2010, 2011 Red Hat, Inc.
> + * Copyright (C) 2009, 2010, 2011 Amit Shah <amit.shah@redhat.com>
> + * Copyright (C) 2021 Ahmad Fatoum
> + * Copyright (C) 2021, Google LLC, schuffelen@google.com (A. Cody Schuffelen)
> + * Copyright (C) 2023, Linaro
> + */
> +
> +#include <common.h>
> +#include <blk.h>
> +#include <dm.h>
> +#include <part.h>
> +#include <serial.h>
> +#include <virtio_types.h>
> +#include <virtio.h>
> +#include <virtio_ring.h>
> +#include "virtio_blk.h"
> +
> +struct virtio_console_priv {
> +	struct virtqueue *receiveq_port0;
> +	struct virtqueue *transmitq_port0;
> +	unsigned char inbuf[1] __aligned(4);
> +};
> +
> +static int virtio_console_bind(struct udevice *dev)
> +{
> +	struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(dev->parent);
> +
> +	/* Indicate what driver features we support */
> +	virtio_driver_features_init(uc_priv, NULL, 0, NULL, 0);
> +
> +	return 0;
> +}
> +
> +/*
> + * Create a scatter-gather list representing our input buffer and put
> + * it in the queue.
> + */
> +static void add_inbuf(struct virtio_console_priv *priv)
> +{
> +	struct virtio_sg sg;
> +	struct virtio_sg *sgs[1];
> +	int ret;
> +
> +	sgs[0] = &sg;
> +	sg.addr = priv->inbuf;
> +	sg.length = sizeof(priv->inbuf);
> +
> +	ret = virtqueue_add(priv->receiveq_port0, sgs, 0, 1);
> +	/* We should always be able to add one buffer to an empty queue. */
> +	WARN(ret < 0, "%s: virtqueue_add failed\n", __func__);
> +
> +	virtqueue_kick(priv->receiveq_port0);
> +}
> +
> +static int virtio_console_probe(struct udevice *dev)
> +{
> +	struct virtio_console_priv *priv = dev_get_priv(dev);
> +	int ret;
> +
> +	struct virtqueue *virtqueues[2];
> +
> +	ret = virtio_find_vqs(dev, 2, virtqueues);
> +	if (ret < 0) {
> +		debug("%s: virtio_find_vqs failed\n", __func__);
> +		return ret;
> +	}
> +
> +	priv->receiveq_port0 = virtqueues[0];
> +	priv->transmitq_port0 = virtqueues[1];
> +
> +	/* Register the input buffer the first time. */
> +	add_inbuf(priv);
> +
> +	return 0;
> +}
> +
> +static int virtio_console_serial_setbrg(struct udevice *dev, int baudrate)
> +{
> +	return 0;
> +}
> +
> +static int virtio_console_serial_pending(struct udevice *dev, bool input)
> +{
> +	struct virtio_console_priv *priv = dev_get_priv(dev);
> +
> +	return virtqueue_poll(priv->receiveq_port0,
> +			      priv->receiveq_port0->last_used_idx);
> +}
> +
> +static int virtio_console_serial_getc(struct udevice *dev)
> +{
> +	struct virtio_console_priv *priv = dev_get_priv(dev);
> +	unsigned char *in;
> +	int ch;
> +	unsigned int len = 0;
> +
> +	in = virtqueue_get_buf(priv->receiveq_port0, &len);
> +	if (!in)
> +		return -EAGAIN;
> +
> +	WARN(len != 1, "%s: too much data: %d\n", __func__, len);
> +
> +	ch = *in;
> +
> +	add_inbuf(priv);
> +
> +	return ch;
> +}
> +
> +static int virtio_console_serial_putc(struct udevice *dev, const char ch)
> +{
> +	struct virtio_console_priv *priv = dev_get_priv(dev);
> +	struct virtio_sg sg;
> +	struct virtio_sg *sgs[1];
> +	unsigned char buf[1] __aligned(4);
> +	int ret = 0;
> +
> +	sg.addr = buf;
> +	sg.length = sizeof(buf);
> +	sgs[0] = &sg;
> +	buf[0] = ch;
> +
> +	ret = virtqueue_add(priv->transmitq_port0, sgs, 1, 0);
> +	if (ret) {
> +		debug("%s: virtqueue_add failed\n", __func__);
> +		return ret;
> +	}
> +
> +	virtqueue_kick(priv->transmitq_port0);
> +
> +	while (!virtqueue_get_buf(priv->transmitq_port0, NULL))
> +		;
> +
> +	return 0;
> +}
> +
> +static const struct dm_serial_ops virtio_console_serial_ops = {
> +	.putc = virtio_console_serial_putc,
> +	.pending = virtio_console_serial_pending,
> +	.getc = virtio_console_serial_getc,
> +	.setbrg = virtio_console_serial_setbrg,
> +};
> +
> +U_BOOT_DRIVER(virtio_console) = {
> +	.name	= VIRTIO_CONSOLE_DRV_NAME,
> +	.id	= UCLASS_SERIAL,
> +	.ops	= &virtio_console_serial_ops,
> +	.bind	= virtio_console_bind,
> +	.probe	= virtio_console_probe,
> +	.remove	= virtio_reset,
> +	.priv_auto	= sizeof(struct virtio_console_priv),
> +	.flags	= DM_FLAG_ACTIVE_DMA,
> +};
> diff --git a/include/virtio.h b/include/virtio.h
> index 062a24630c..e36dd41fd1 100644
> --- a/include/virtio.h
> +++ b/include/virtio.h
> @@ -25,11 +25,13 @@
>  #include <linux/bug.h>
>  #define VIRTIO_ID_NET		1 /* virtio net */
>  #define VIRTIO_ID_BLOCK		2 /* virtio block */
> +#define VIRTIO_ID_CONSOLE	3 /* virtio console */
>  #define VIRTIO_ID_RNG		4 /* virtio rng */
>  #define VIRTIO_ID_MAX_NUM	5
>  
>  #define VIRTIO_NET_DRV_NAME	"virtio-net"
>  #define VIRTIO_BLK_DRV_NAME	"virtio-blk"
> +#define VIRTIO_CONSOLE_DRV_NAME	"virtio-console"
>  #define VIRTIO_RNG_DRV_NAME	"virtio-rng"
>  
>  /* Status byte for guest to report progress, and synchronize features */