Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=31610434bc3523c0b01a10917a1185096a03c4c8
Commit:     31610434bc3523c0b01a10917a1185096a03c4c8
Parent:     e467cde238184d1b0923db2cd61ae1c5a6dc15aa
Author:     Rusty Russell <[EMAIL PROTECTED]>
AuthorDate: Mon Oct 22 11:03:39 2007 +1000
Committer:  Rusty Russell <[EMAIL PROTECTED]>
CommitDate: Tue Oct 23 15:49:55 2007 +1000

    Virtio console driver
    
    This is an hvc-based virtio console driver.  It's suboptimal becuase
    hvc expects to have raw access to interrupts and virtio doesn't assume
    that, so it currently polls.
    
    There are two solutions: expose hvc's "kick" interface, or wean off hvc.
    
    Signed-off-by: Rusty Russell <[EMAIL PROTECTED]>
---
 drivers/char/Kconfig           |    4 +
 drivers/char/Makefile          |    1 +
 drivers/char/virtio_console.c  |  225 ++++++++++++++++++++++++++++++++++++++++
 include/linux/virtio_console.h |   12 ++
 4 files changed, 242 insertions(+), 0 deletions(-)

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 6549110..bf18d75 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -613,6 +613,10 @@ config HVC_XEN
        help
          Xen virtual console device driver
 
+config VIRTIO_CONSOLE
+       bool
+       select HVC_DRIVER
+
 config HVCS
        tristate "IBM Hypervisor Virtual Console Server support"
        depends on PPC_PSERIES
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index c78ff26..057c8bb 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_HVC_RTAS)                += hvc_rtas.o
 obj-$(CONFIG_HVC_BEAT)         += hvc_beat.o
 obj-$(CONFIG_HVC_DRIVER)       += hvc_console.o
 obj-$(CONFIG_HVC_XEN)          += hvc_xen.o
+obj-$(CONFIG_VIRTIO_CONSOLE)   += virtio_console.o
 obj-$(CONFIG_RAW_DRIVER)       += raw.o
 obj-$(CONFIG_SGI_SNSC)         += snsc.o snsc_event.o
 obj-$(CONFIG_MSPEC)            += mspec.o
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
new file mode 100644
index 0000000..100e8a2
--- /dev/null
+++ b/drivers/char/virtio_console.c
@@ -0,0 +1,225 @@
+/*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;
+
+/*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);
+}
+
+/*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 virtcons_probe(struct virtio_device *dev)
+{
+       int err;
+       struct hvc_struct *hvc;
+
+       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 input queue. */
+       /* FIXME: This is why we want to wean off hvc: we do nothing
+        * when input comes in. */
+       in_vq = vdev->config->find_vq(vdev, NULL);
+       if (IS_ERR(in_vq)) {
+               err = PTR_ERR(in_vq);
+               goto free;
+       }
+
+       out_vq = vdev->config->find_vq(vdev, NULL);
+       if (IS_ERR(out_vq)) {
+               err = PTR_ERR(out_vq);
+               goto free_in_vq;
+       }
+
+       /* Start using the new console output. */
+       virtio_cons.get_chars = get_chars;
+       virtio_cons.put_chars = put_chars;
+
+       /* The first argument of hvc_alloc() is the virtual console number, so
+        * we use zero.  The second argument is the interrupt number; we
+        * currently leave this as zero: it would be better not to use the
+        * hvc mechanism and fix this (FIXME!).
+        *
+        * The third argument is a "struct hv_ops" containing the put_chars()
+        * and get_chars() 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_out_vq;
+       }
+
+       /* Register the input buffer the first time. */
+       add_inbuf();
+       return 0;
+
+free_out_vq:
+       vdev->config->del_vq(out_vq);
+free_in_vq:
+       vdev->config->del_vq(in_vq);
+free:
+       kfree(inbuf);
+fail:
+       return err;
+}
+
+static struct virtio_device_id id_table[] = {
+       { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
+       { 0 },
+};
+
+static struct virtio_driver virtio_console = {
+       .driver.name =  KBUILD_MODNAME,
+       .driver.owner = THIS_MODULE,
+       .id_table =     id_table,
+       .probe =        virtcons_probe,
+};
+
+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");
diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
new file mode 100644
index 0000000..ed2d4ea
--- /dev/null
+++ b/include/linux/virtio_console.h
@@ -0,0 +1,12 @@
+#ifndef _LINUX_VIRTIO_CONSOLE_H
+#define _LINUX_VIRTIO_CONSOLE_H
+#include <linux/virtio_config.h>
+
+/* The ID for virtio console */
+#define VIRTIO_ID_CONSOLE      3
+
+#ifdef __KERNEL__
+int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_VIRTIO_CONSOLE_H */
-
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