-/*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
+/*
+ * Copyright (C) 2006, 2007, 2009 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
#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;
/* The hvc device */
static struct hvc_struct *hvc;
-/*D:310 The put_chars() callback is pretty straightforward.
+/*
+ * 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). */
+ * 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];
/* 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. */
+ /*
+ * 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);
return count;
}
-/* Create a scatter-gather list representing our input buffer and put it in the
- * queue. */
+/*
+ * Create a scatter-gather list representing our input buffer and put
+ * it in the queue.
+ */
static void add_inbuf(void)
{
struct scatterlist sg[1];
in_vq->vq_ops->kick(in_vq);
}
-/*D:350 get_chars() is the callback from the hvc_console infrastructure when
- * an interrupt is received.
+/*
+ * 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. */
+ * 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. */
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.
+/*
+ * 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. */
+ * 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;
}
/*
- * 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
+ * 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)
{
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.
+/*
+ * 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.
+ * 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. */
+ * 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};
}
/* 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;
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 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. */
+ * 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);
git://ftp.safe.ca / safe / jmp / linux-2.6 / commitdiff