[linux-block.git] / drivers / char / virtio_console.c

/*D:300
 * The Guest console driver
 *
 * Writing console drivers is one of the few remaining Dark Arts in Linux.
 * Fortunately for us, the path of virtual consoles has been well-trodden by
 * the PowerPC folks, who wrote "hvc_console.c" to generically support any
 * virtual console.  We use that infrastructure which only requires us to write
 * the basic put_chars and get_chars functions and call the right register
 * functions.
 :*/

/*M:002 The console can be flooded: while the Guest is processing input the
 * Host can send more.  Buffering in the Host could alleviate this, but it is a
 * difficult problem in general. :*/
/* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/err.h>
#include <linux/init.h>
#include <linux/virtio.h>
#include <linux/virtio_console.h>
#include "hvc_console.h"

/*D:340 These represent our input and output console queues, and the virtio
 * operations for them. */
static struct virtqueue *in_vq, *out_vq;
static struct virtio_device *vdev;

/* This is our input buffer, and how much data is left in it. */
static unsigned int in_len;
static char *in, *inbuf;

/* The operations for our console. */
static struct hv_ops virtio_cons;

/* The hvc device */
static struct hvc_struct *hvc;

/*D:310 The put_chars() callback is pretty straightforward.
 *
 * We turn the characters into a scatter-gather list, add it to the output
 * queue and then kick the Host.  Then we sit here waiting for it to finish:
 * inefficient in theory, but in practice implementations will do it
 * immediately (lguest's Launcher does). */
static int put_chars(u32 vtermno, const char *buf, int count)
{
	struct scatterlist sg[1];
	unsigned int len;

	/* This is a convenient routine to initialize a single-elem sg list */
	sg_init_one(sg, buf, count);

	/* add_buf wants a token to identify this buffer: we hand it any
	 * non-NULL pointer, since there's only ever one buffer. */
	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
		/* Tell Host to go! */
		out_vq->vq_ops->kick(out_vq);
		/* Chill out until it's done with the buffer. */
		while (!out_vq->vq_ops->get_buf(out_vq, &len))
			cpu_relax();
	}

	/* We're expected to return the amount of data we wrote: all of it. */
	return count;
}

/* Create a scatter-gather list representing our input buffer and put it in the
 * queue. */
static void add_inbuf(void)
{
	struct scatterlist sg[1];
	sg_init_one(sg, inbuf, PAGE_SIZE);

	/* We should always be able to add one buffer to an empty queue. */
	if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0)
		BUG();
	in_vq->vq_ops->kick(in_vq);
}

/*D:350 get_chars() is the callback from the hvc_console infrastructure when
 * an interrupt is received.
 *
 * Most of the code deals with the fact that the hvc_console() infrastructure
 * only asks us for 16 bytes at a time.  We keep in_offset and in_used fields
 * for partially-filled buffers. */
static int get_chars(u32 vtermno, char *buf, int count)
{
	/* If we don't have an input queue yet, we can't get input. */
	BUG_ON(!in_vq);

	/* No buffer?  Try to get one. */
	if (!in_len) {
		in = in_vq->vq_ops->get_buf(in_vq, &in_len);
		if (!in)
			return 0;
	}

	/* You want more than we have to give?  Well, try wanting less! */
	if (in_len < count)
		count = in_len;

	/* Copy across to their buffer and increment offset. */
	memcpy(buf, in, count);
	in += count;
	in_len -= count;

	/* Finished?  Re-register buffer so Host will use it again. */
	if (in_len == 0)
		add_inbuf();

	return count;
}
/*:*/

/*D:320 Console drivers are initialized very early so boot messages can go out,
 * so we do things slightly differently from the generic virtio initialization
 * of the net and block drivers.
 *
 * At this stage, the console is output-only.  It's too early to set up a
 * virtqueue, so we let the drivers do some boutique early-output thing. */
int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
{
	virtio_cons.put_chars = put_chars;
	return hvc_instantiate(0, 0, &virtio_cons);
}

/*
 * virtio console configuration. This supports:
 * - console resize
 */
static void virtcons_apply_config(struct virtio_device *dev)
{
	struct winsize ws;

	if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) {
		dev->config->get(dev,
				 offsetof(struct virtio_console_config, cols),
				 &ws.ws_col, sizeof(u16));
		dev->config->get(dev,
				 offsetof(struct virtio_console_config, rows),
				 &ws.ws_row, sizeof(u16));
		hvc_resize(hvc, ws);
	}
}

/*
 * we support only one console, the hvc struct is a global var
 * We set the configuration at this point, since we now have a tty
 */
static int notifier_add_vio(struct hvc_struct *hp, int data)
{
	hp->irq_requested = 1;
	virtcons_apply_config(vdev);

	return 0;
}

static void notifier_del_vio(struct hvc_struct *hp, int data)
{
	hp->irq_requested = 0;
}

static void hvc_handle_input(struct virtqueue *vq)
{
	if (hvc_poll(hvc))
		hvc_kick();
}

/*D:370 Once we're further in boot, we get probed like any other virtio device.
 * At this stage we set up the output virtqueue.
 *
 * To set up and manage our virtual console, we call hvc_alloc().  Since we
 * never remove the console device we never need this pointer again.
 *
 * Finally we put our input buffer in the input queue, ready to receive. */
static int __devinit virtcons_probe(struct virtio_device *dev)
{
	vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
	const char *names[] = { "input", "output" };
	struct virtqueue *vqs[2];
	int err;

	vdev = dev;

	/* This is the scratch page we use to receive console input */
	inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!inbuf) {
		err = -ENOMEM;
		goto fail;
	}

	/* Find the queues. */
	/* FIXME: This is why we want to wean off hvc: we do nothing
	 * when input comes in. */
	err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
	if (err)
		goto free;

	in_vq = vqs[0];
	out_vq = vqs[1];

	/* Start using the new console output. */
	virtio_cons.get_chars = get_chars;
	virtio_cons.put_chars = put_chars;
	virtio_cons.notifier_add = notifier_add_vio;
	virtio_cons.notifier_del = notifier_del_vio;
	virtio_cons.notifier_hangup = notifier_del_vio;

	/* The first argument of hvc_alloc() is the virtual console number, so
	 * we use zero.  The second argument is the parameter for the
	 * notification mechanism (like irq number). We currently leave this
	 * as zero, virtqueues have implicit notifications.
	 *
	 * The third argument is a "struct hv_ops" containing the put_chars()
	 * get_chars(), notifier_add() and notifier_del() pointers.
	 * The final argument is the output buffer size: we can do any size,
	 * so we put PAGE_SIZE here. */
	hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
	if (IS_ERR(hvc)) {
		err = PTR_ERR(hvc);
		goto free_vqs;
	}

	/* Register the input buffer the first time. */
	add_inbuf();
	return 0;

free_vqs:
	vdev->config->del_vqs(vdev);
free:
	kfree(inbuf);
fail:
	return err;
}

static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
	{ 0 },
};

static unsigned int features[] = {
	VIRTIO_CONSOLE_F_SIZE,
};

static struct virtio_driver virtio_console = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.driver.name =	KBUILD_MODNAME,
	.driver.owner =	THIS_MODULE,
	.id_table =	id_table,
	.probe =	virtcons_probe,
	.config_changed = virtcons_apply_config,
};

static int __init init(void)
{
	return register_virtio_driver(&virtio_console);
}
module_init(init);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio console driver");
MODULE_LICENSE("GPL");
Commit	Line	Data
31610434 RR	1	/*D:300
	2	* The Guest console driver
	3	*
	4	* Writing console drivers is one of the few remaining Dark Arts in Linux.
	5	* Fortunately for us, the path of virtual consoles has been well-trodden by
	6	* the PowerPC folks, who wrote "hvc_console.c" to generically support any
	7	* virtual console. We use that infrastructure which only requires us to write
	8	* the basic put_chars and get_chars functions and call the right register
	9	* functions.
	10	:*/
	11
	12	/*M:002 The console can be flooded: while the Guest is processing input the
	13	* Host can send more. Buffering in the Host could alleviate this, but it is a
	14	* difficult problem in general. :*/
	15	/* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
	16	*
	17	* This program is free software; you can redistribute it and/or modify
	18	* it under the terms of the GNU General Public License as published by
	19	* the Free Software Foundation; either version 2 of the License, or
	20	* (at your option) any later version.
	21	*
	22	* This program is distributed in the hope that it will be useful,
	23	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	24	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	25	* GNU General Public License for more details.
	26	*
	27	* You should have received a copy of the GNU General Public License
	28	* along with this program; if not, write to the Free Software
	29	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	30	*/
	31	#include <linux/err.h>
	32	#include <linux/init.h>
	33	#include <linux/virtio.h>
	34	#include <linux/virtio_console.h>
	35	#include "hvc_console.h"
	36
	37	/*D:340 These represent our input and output console queues, and the virtio
	38	* operations for them. */
	39	static struct virtqueue in_vq, out_vq;
	40	static struct virtio_device *vdev;
	41
	42	/* This is our input buffer, and how much data is left in it. */
	43	static unsigned int in_len;
	44	static char in, inbuf;
	45
	46	/* The operations for our console. */
	47	static struct hv_ops virtio_cons;
	48
91fcad19 CB	49	/* The hvc device */
	50	static struct hvc_struct *hvc;
	51
31610434 RR	52	/*D:310 The put_chars() callback is pretty straightforward.
	53	*
	54	* We turn the characters into a scatter-gather list, add it to the output
	55	* queue and then kick the Host. Then we sit here waiting for it to finish:
	56	* inefficient in theory, but in practice implementations will do it
	57	* immediately (lguest's Launcher does). */
	58	static int put_chars(u32 vtermno, const char *buf, int count)
	59	{
	60	struct scatterlist sg[1];
	61	unsigned int len;
	62
	63	/* This is a convenient routine to initialize a single-elem sg list */
	64	sg_init_one(sg, buf, count);
	65
	66	/* add_buf wants a token to identify this buffer: we hand it any
	67	* non-NULL pointer, since there's only ever one buffer. */
	68	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
	69	/* Tell Host to go! */
	70	out_vq->vq_ops->kick(out_vq);
	71	/* Chill out until it's done with the buffer. */
	72	while (!out_vq->vq_ops->get_buf(out_vq, &len))
	73	cpu_relax();
	74	}
	75
	76	/* We're expected to return the amount of data we wrote: all of it. */
	77	return count;
	78	}
	79
	80	/* Create a scatter-gather list representing our input buffer and put it in the
	81	* queue. */
	82	static void add_inbuf(void)
	83	{
	84	struct scatterlist sg[1];
	85	sg_init_one(sg, inbuf, PAGE_SIZE);
	86
	87	/* We should always be able to add one buffer to an empty queue. */
	88	if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0)
	89	BUG();
	90	in_vq->vq_ops->kick(in_vq);
	91	}
	92
	93	/*D:350 get_chars() is the callback from the hvc_console infrastructure when
	94	* an interrupt is received.
	95	*
	96	* Most of the code deals with the fact that the hvc_console() infrastructure
	97	* only asks us for 16 bytes at a time. We keep in_offset and in_used fields
	98	* for partially-filled buffers. */
	99	static int get_chars(u32 vtermno, char *buf, int count)
	100	{
	101	/* If we don't have an input queue yet, we can't get input. */
	102	BUG_ON(!in_vq);
	103
	104	/* No buffer? Try to get one. */
	105	if (!in_len) {
	106	in = in_vq->vq_ops->get_buf(in_vq, &in_len);
	107	if (!in)
	108	return 0;
	109	}
	110
	111	/* You want more than we have to give? Well, try wanting less! */
	112	if (in_len < count)
	113	count = in_len;
	114
	115	/* Copy across to their buffer and increment offset. */
116	memcpy(buf, in, count);
117	in += count;
118	in_len -= count;
119
120	/* Finished? Re-register buffer so Host will use it again. */
121	if (in_len == 0)
122	add_inbuf();
123
124	return count;
125	}
126	/:/
127
128	/*D:320 Console drivers are initialized very early so boot messages can go out,
129	* so we do things slightly differently from the generic virtio initialization
130	* of the net and block drivers.
131	*
132	* At this stage, the console is output-only. It's too early to set up a
133	* virtqueue, so we let the drivers do some boutique early-output thing. */
134	int __init virtio_cons_early_init(int (put_chars)(u32, const char , int))
135	{
136	virtio_cons.put_chars = put_chars;
137	return hvc_instantiate(0, 0, &virtio_cons);
138	}
139
c2983458 CB	140	/*
	141	* virtio console configuration. This supports:
	142	* - console resize
	143	*/
	144	static void virtcons_apply_config(struct virtio_device *dev)
	145	{
	146	struct winsize ws;
	147
	148	if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) {
	149	dev->config->get(dev,
	150	offsetof(struct virtio_console_config, cols),
	151	&ws.ws_col, sizeof(u16));
	152	dev->config->get(dev,
	153	offsetof(struct virtio_console_config, rows),
	154	&ws.ws_row, sizeof(u16));
	155	hvc_resize(hvc, ws);
	156	}
	157	}
	158
91fcad19 CB	159	/*
91fcad19 CB	160	* we support only one console, the hvc struct is a global var
c2983458	161	* We set the configuration at this point, since we now have a tty
91fcad19 CB	162	*/
	163	static int notifier_add_vio(struct hvc_struct *hp, int data)
	164	{
	165	hp->irq_requested = 1;
c2983458 CB	166	virtcons_apply_config(vdev);
c2983458 CB	167
91fcad19 CB	168	return 0;
	169	}
	170
	171	static void notifier_del_vio(struct hvc_struct *hp, int data)
	172	{
	173	hp->irq_requested = 0;
	174	}
	175
	176	static void hvc_handle_input(struct virtqueue *vq)
	177	{
	178	if (hvc_poll(hvc))
	179	hvc_kick();
	180	}
	181
31610434 RR	182	/*D:370 Once we're further in boot, we get probed like any other virtio device.
	183	* At this stage we set up the output virtqueue.
	184	*
	185	* To set up and manage our virtual console, we call hvc_alloc(). Since we
	186	* never remove the console device we never need this pointer again.
	187	*
	188	* Finally we put our input buffer in the input queue, ready to receive. */
139b8298	189	static int __devinit virtcons_probe(struct virtio_device *dev)
31610434	190	{
d2a7ddda MT	191	vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
	192	const char *names[] = { "input", "output" };
	193	struct virtqueue *vqs[2];
31610434	194	int err;
31610434 RR	195
	196	vdev = dev;
	197
	198	/* This is the scratch page we use to receive console input */
	199	inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	200	if (!inbuf) {
	201	err = -ENOMEM;
	202	goto fail;
	203	}
	204
d2a7ddda	205	/* Find the queues. */
31610434 RR	206	/* FIXME: This is why we want to wean off hvc: we do nothing
31610434 RR	207	* when input comes in. */
d2a7ddda MT	208	err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
d2a7ddda MT	209	if (err)
31610434	210	goto free;
31610434	211
d2a7ddda MT	212	in_vq = vqs[0];
d2a7ddda MT	213	out_vq = vqs[1];
31610434 RR	214
	215	/* Start using the new console output. */
	216	virtio_cons.get_chars = get_chars;
	217	virtio_cons.put_chars = put_chars;
91fcad19 CB	218	virtio_cons.notifier_add = notifier_add_vio;
91fcad19 CB	219	virtio_cons.notifier_del = notifier_del_vio;
fc362e2e	220	virtio_cons.notifier_hangup = notifier_del_vio;
31610434 RR	221
31610434 RR	222	/* The first argument of hvc_alloc() is the virtual console number, so
91fcad19 CB	223	* we use zero. The second argument is the parameter for the
	224	* notification mechanism (like irq number). We currently leave this
	225	* as zero, virtqueues have implicit notifications.
31610434 RR	226	*
31610434 RR	227	* The third argument is a "struct hv_ops" containing the put_chars()
91fcad19 CB	228	* get_chars(), notifier_add() and notifier_del() pointers.
	229	* The final argument is the output buffer size: we can do any size,
	230	* so we put PAGE_SIZE here. */
31610434 RR	231	hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
	232	if (IS_ERR(hvc)) {
	233	err = PTR_ERR(hvc);
d2a7ddda	234	goto free_vqs;
31610434 RR	235	}
	236
	237	/* Register the input buffer the first time. */
	238	add_inbuf();
	239	return 0;
	240
d2a7ddda MT	241	free_vqs:
d2a7ddda MT	242	vdev->config->del_vqs(vdev);
31610434 RR	243	free:
	244	kfree(inbuf);
	245	fail:
	246	return err;
	247	}
	248
	249	static struct virtio_device_id id_table[] = {
	250	{ VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
	251	{ 0 },
	252	};
	253
c2983458 CB	254	static unsigned int features[] = {
	255	VIRTIO_CONSOLE_F_SIZE,
	256	};
	257
31610434	258	static struct virtio_driver virtio_console = {
c2983458 CB	259	.feature_table = features,
c2983458 CB	260	.feature_table_size = ARRAY_SIZE(features),
31610434 RR	261	.driver.name = KBUILD_MODNAME,
	262	.driver.owner = THIS_MODULE,
	263	.id_table = id_table,
	264	.probe = virtcons_probe,
c2983458	265	.config_changed = virtcons_apply_config,
31610434 RR	266	};
	267
	268	static int __init init(void)
	269	{
	270	return register_virtio_driver(&virtio_console);
	271	}
	272	module_init(init);
	273
	274	MODULE_DEVICE_TABLE(virtio, id_table);
	275	MODULE_DESCRIPTION("Virtio console driver");
	276	MODULE_LICENSE("GPL");