virtio: console: port encapsulation

We are heading towards a multiple-"port" system, so as part of weaning off
globals we encapsulate the information into 'struct port'.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/char/virtio_console.c

@@ -21,15 +21,19 @@
 #include <linux/virtio_console.h>
 #include "hvc_console.h"
 
-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;
+struct port {
+	struct virtqueue *in_vq, *out_vq;
+	struct virtio_device *vdev;
+	/* This is our input buffer, and how much data is left in it. */
+	char *inbuf;
+	unsigned int used_len, offset;
+
+	/* The hvc device */
+	struct hvc_struct *hvc;
+};
 
-/* The hvc device */
-static struct hvc_struct *hvc;
+/* We have one port ready to go immediately, for a console. */
+static struct port console;
 
 /* This is the very early arch-specified put chars function. */
 static int (*early_put_chars)(u32, const char *, int);
@@ -46,22 +50,21 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 {
 	struct scatterlist sg[1];
 	unsigned int len;
+	struct port *port;
 
 	if (unlikely(early_put_chars))
 		return early_put_chars(vtermno, buf, count);
 
+	port = &console;
+
 	/* 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) {
+	/* This shouldn't fail: if it does, we lose chars. */
+	if (port->out_vq->vq_ops->add_buf(port->out_vq, sg, 1, 0, port) >= 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))
+		port->out_vq->vq_ops->kick(port->out_vq);
+		while (!port->out_vq->vq_ops->get_buf(port->out_vq, &len))
 			cpu_relax();
 	}
 
@@ -73,15 +76,15 @@ static int put_chars(u32 vtermno, const char *buf, int count)
  * Create a scatter-gather list representing our input buffer and put
  * it in the queue.
  */
-static void add_inbuf(void)
+static void add_inbuf(struct port *port)
 {
 	struct scatterlist sg[1];
-	sg_init_one(sg, inbuf, PAGE_SIZE);
+	sg_init_one(sg, port->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)
+	/* Should always be able to add one buffer to an empty queue. */
+	if (port->in_vq->vq_ops->add_buf(port->in_vq, sg, 0, 1, port) < 0)
 		BUG();
-	in_vq->vq_ops->kick(in_vq);
+	port->in_vq->vq_ops->kick(port->in_vq);
 }
 
 /*
@@ -94,28 +97,31 @@ static void add_inbuf(void)
  */
 static int get_chars(u32 vtermno, char *buf, int count)
 {
+	struct port *port;
+
+	port = &console;
+
 	/* If we don't have an input queue yet, we can't get input. */
-	BUG_ON(!in_vq);
+	BUG_ON(!port->in_vq);
 
-	/* No buffer?  Try to get one. */
-	if (!in_len) {
-		in = in_vq->vq_ops->get_buf(in_vq, &in_len);
-		if (!in)
+	/* No more in buffer?  See if they've (re)used it. */
+	if (port->offset == port->used_len) {
+		if (!port->in_vq->vq_ops->get_buf(port->in_vq, &port->used_len))
 			return 0;
+		port->offset = 0;
 	}
 
 	/* You want more than we have to give?  Well, try wanting less! */
-	if (in_len < count)
-		count = in_len;
+	if (port->offset + count > port->used_len)
+		count = port->used_len - port->offset;
 
 	/* Copy across to their buffer and increment offset. */
-	memcpy(buf, in, count);
-	in += count;
-	in_len -= count;
+	memcpy(buf, port->inbuf + port->offset, count);
+	port->offset += count;
 
 	/* Finished?  Re-register buffer so Host will use it again. */
-	if (in_len == 0)
-		add_inbuf();
+	if (port->offset == port->used_len)
+		add_inbuf(port);
 
 	return count;
 }
@@ -135,7 +141,7 @@ static void virtcons_apply_config(struct virtio_device *dev)
 		dev->config->get(dev,
 				 offsetof(struct virtio_console_config, rows),
 				 &ws.ws_row, sizeof(u16));
-		hvc_resize(hvc, ws);
+		hvc_resize(console.hvc, ws);
 	}
 }
 
@@ -146,7 +152,7 @@ static void virtcons_apply_config(struct virtio_device *dev)
 static int notifier_add_vio(struct hvc_struct *hp, int data)
 {
 	hp->irq_requested = 1;
-	virtcons_apply_config(vdev);
+	virtcons_apply_config(console.vdev);
 
 	return 0;
 }
@@ -158,7 +164,7 @@ static void notifier_del_vio(struct hvc_struct *hp, int data)
 
 static void hvc_handle_input(struct virtqueue *vq)
 {
-	if (hvc_poll(hvc))
+	if (hvc_poll(console.hvc))
 		hvc_kick();
 }
 
@@ -197,23 +203,26 @@ int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
  * Finally we put our input buffer in the input queue, ready to
  * receive.
  */
-static int __devinit virtcons_probe(struct virtio_device *dev)
+static int __devinit virtcons_probe(struct virtio_device *vdev)
 {
 	vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
 	const char *names[] = { "input", "output" };
 	struct virtqueue *vqs[2];
+	struct port *port;
 	int err;
 
-	if (vdev) {
-		dev_warn(&vdev->dev,
+	port = &console;
+	if (port->vdev) {
+		dev_warn(&port->vdev->dev,
 			 "Multiple virtio-console devices not supported yet\n");
 		return -EEXIST;
 	}
-	vdev = dev;
+	port->vdev = vdev;
 
 	/* This is the scratch page we use to receive console input */
-	inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
-	if (!inbuf) {
+	port->used_len = 0;
+	port->inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!port->inbuf) {
 		err = -ENOMEM;
 		goto fail;
 	}
@@ -223,8 +232,8 @@ static int __devinit virtcons_probe(struct virtio_device *dev)
 	if (err)
 		goto free;
 
-	in_vq = vqs[0];
-	out_vq = vqs[1];
+	port->in_vq = vqs[0];
+	port->out_vq = vqs[1];
 
 	/*
 	 * The first argument of hvc_alloc() is the virtual console
@@ -238,14 +247,14 @@ static int __devinit virtcons_probe(struct virtio_device *dev)
 	 * 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, &hv_ops, PAGE_SIZE);
-	if (IS_ERR(hvc)) {
-		err = PTR_ERR(hvc);
+	port->hvc = hvc_alloc(0, 0, &hv_ops, PAGE_SIZE);
+	if (IS_ERR(port->hvc)) {
+		err = PTR_ERR(port->hvc);
 		goto free_vqs;
 	}
 
 	/* Register the input buffer the first time. */
-	add_inbuf();
+	add_inbuf(port);
 
 	/* Start using the new console output. */
 	early_put_chars = NULL;
@@ -254,7 +263,7 @@ static int __devinit virtcons_probe(struct virtio_device *dev)
 free_vqs:
 	vdev->config->del_vqs(vdev);
 free:
-	kfree(inbuf);
+	kfree(port->inbuf);
 fail:
 	return err;
 }