virtio: console: encapsulate buffer information in a struct

Collect port buffer, used_len, offset fields into a single structure.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 55 insertions, 15 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 9ea9223c5c5c..699fc98ec8d9 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -21,12 +21,24 @@
 #include <linux/virtio_console.h>
 #include "hvc_console.h"
 
+struct port_buffer {
+        char *buf;
+
+        /* size of the buffer in *buf above */
+        size_t size;
+
+        /* used length of the buffer */
+        size_t len;
+        /* offset in the buf from which to consume data */
+        size_t offset;
+};
+
 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 current buffer from which data has to be fed to readers */
+        struct port_buffer *inbuf;
 
         /* The hvc device */
         struct hvc_struct *hvc;
@@ -38,6 +50,33 @@ static struct port console;
 /* This is the very early arch-specified put chars function. */
 static int (*early_put_chars)(u32, const char *, int);
 
+static void free_buf(struct port_buffer *buf)
+{
+        kfree(buf->buf);
+        kfree(buf);
+}
+
+static struct port_buffer *alloc_buf(size_t buf_size)
+{
+        struct port_buffer *buf;
+
+        buf = kmalloc(sizeof(*buf), GFP_KERNEL);
+        if (!buf)
+                goto fail;
+        buf->buf = kzalloc(buf_size, GFP_KERNEL);
+        if (!buf->buf)
+                goto free_buf;
+        buf->len = 0;
+        buf->offset = 0;
+        buf->size = buf_size;
+        return buf;
+
+free_buf:
+        kfree(buf);
+fail:
+        return NULL;
+}
+
 /*
  * The put_chars() callback is pretty straightforward.
  *
@@ -79,7 +118,7 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 static void add_inbuf(struct port *port)
 {
         struct scatterlist sg[1];
-        sg_init_one(sg, port->inbuf, PAGE_SIZE);
+        sg_init_one(sg, port->inbuf->buf, PAGE_SIZE);
 
         /* 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)
@@ -98,6 +137,7 @@ static void add_inbuf(struct port *port)
 static int get_chars(u32 vtermno, char *buf, int count)
 {
         struct port *port;
+        unsigned int len;
 
         port = &console;
 
@@ -105,22 +145,23 @@ static int get_chars(u32 vtermno, char *buf, int count)
         BUG_ON(!port->in_vq);
 
         /* 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))
+        if (port->inbuf->offset == port->inbuf->len) {
+                if (!port->in_vq->vq_ops->get_buf(port->in_vq, &len))
                         return 0;
-                port->offset = 0;
+                port->inbuf->offset = 0;
+                port->inbuf->len = len;
         }
 
         /* You want more than we have to give?  Well, try wanting less! */
-        if (port->offset + count > port->used_len)
-                count = port->used_len - port->offset;
+        if (port->inbuf->offset + count > port->inbuf->len)
+                count = port->inbuf->len - port->inbuf->offset;
 
         /* Copy across to their buffer and increment offset. */
-        memcpy(buf, port->inbuf + port->offset, count);
-        port->offset += count;
+        memcpy(buf, port->inbuf->buf + port->inbuf->offset, count);
+        port->inbuf->offset += count;
 
         /* Finished?  Re-register buffer so Host will use it again. */
-        if (port->offset == port->used_len)
+        if (port->inbuf->offset == port->inbuf->len)
                 add_inbuf(port);
 
         return count;
@@ -220,8 +261,7 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
         port->vdev = vdev;
 
         /* This is the scratch page we use to receive console input */
-        port->used_len = 0;
-        port->inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+        port->inbuf = alloc_buf(PAGE_SIZE);
         if (!port->inbuf) {
                 err = -ENOMEM;
                 goto fail;
@@ -263,7 +303,7 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
 free_vqs:
         vdev->config->del_vqs(vdev);
 free:
-        kfree(port->inbuf);
+        free_buf(port->inbuf);
 fail:
         return err;
 }