virtio: console: comment cleanup (a23ea924) · Commits · e / devices / android_kernel_teracube_emerald

drivers/char/virtio_console.c

+54 −54

Original line number	Original line	Diff line number	Diff line
	/*D:300		/*
	* The Guest console driver		* Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
	*
	* 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		* 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		* it under the terms of the GNU General Public License as published by
	@@ -34,8 +21,6 @@
	#include <linux/virtio_console.h>		#include <linux/virtio_console.h>
	#include "hvc_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 virtqueue in_vq, out_vq;
	static struct virtio_device *vdev;		static struct virtio_device *vdev;

	@@ -49,12 +34,14 @@ static struct hv_ops virtio_cons;
	/* The hvc device */		/* The hvc device */
	static struct hvc_struct *hvc;		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		* We turn the characters into a scatter-gather list, add it to the
	* queue and then kick the Host. Then we sit here waiting for it to finish:		* output queue and then kick the Host. Then we sit here waiting for
	* inefficient in theory, but in practice implementations will do it		* it to finish: inefficient in theory, but in practice
	* immediately (lguest's Launcher does). */		* implementations will do it immediately (lguest's Launcher does).
			*/
	static int put_chars(u32 vtermno, const char *buf, int count)		static int put_chars(u32 vtermno, const char *buf, int count)
	{		{
	struct scatterlist sg[1];		struct scatterlist sg[1];
	@@ -63,8 +50,10 @@ static int put_chars(u32 vtermno, const char *buf, int count)
	/* This is a convenient routine to initialize a single-elem sg list */		/* This is a convenient routine to initialize a single-elem sg list */
	sg_init_one(sg, buf, count);		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) {		if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) >= 0) {
	/* Tell Host to go! */		/* Tell Host to go! */
	out_vq->vq_ops->kick(out_vq);		out_vq->vq_ops->kick(out_vq);
	@@ -77,8 +66,10 @@ static int put_chars(u32 vtermno, const char *buf, int count)
	return count;		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)		static void add_inbuf(void)
	{		{
	struct scatterlist sg[1];		struct scatterlist sg[1];
	@@ -90,12 +81,14 @@ static void add_inbuf(void)
	in_vq->vq_ops->kick(in_vq);		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		* Most of the code deals with the fact that the hvc_console()
	* only asks us for 16 bytes at a time. We keep in_offset and in_used fields		* infrastructure only asks us for 16 bytes at a time. We keep
	* for partially-filled buffers. */		* in_offset and in_used fields for partially-filled buffers.
			*/
	static int get_chars(u32 vtermno, char *buf, int count)		static int get_chars(u32 vtermno, char *buf, int count)
	{		{
	/* If we don't have an input queue yet, we can't get input. */		/* If we don't have an input queue yet, we can't get input. */
	@@ -123,14 +116,16 @@ static int get_chars(u32 vtermno, char *buf, int count)

	return count;		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		* Console drivers are initialized very early so boot messages can go
	* of the net and block drivers.		* 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		* At this stage, the console is output-only. It's too early to set
	* virtqueue, so we let the drivers do some boutique early-output thing. */		* 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))		int __init virtio_cons_early_init(int (put_chars)(u32, const char , int))
	{		{
	virtio_cons.put_chars = put_chars;		virtio_cons.put_chars = put_chars;
	@@ -157,8 +152,8 @@ static void virtcons_apply_config(struct virtio_device *dev)
	}		}

	/*		/*
	* we support only one console, the hvc struct is a global var		* we support only one console, the hvc struct is a global var We set
	* We set the configuration at this point, since we now have a tty		* the configuration at this point, since we now have a tty
	*/		*/
	static int notifier_add_vio(struct hvc_struct *hp, int data)		static int notifier_add_vio(struct hvc_struct *hp, int data)
	{		{
	@@ -179,13 +174,17 @@ static void hvc_handle_input(struct virtqueue *vq)
	hvc_kick();		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		* To set up and manage our virtual console, we call hvc_alloc().
	* never remove the console device we never need this pointer again.		* 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)		static int __devinit virtcons_probe(struct virtio_device *dev)
	{		{
	vq_callback_t *callbacks[] = { hvc_handle_input, NULL};		vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
	@@ -203,8 +202,6 @@ static int __devinit virtcons_probe(struct virtio_device *dev)
	}		}

	/* Find the queues. */		/* 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);		err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
	if (err)		if (err)
	goto free;		goto free;
	@@ -219,15 +216,18 @@ static int __devinit virtcons_probe(struct virtio_device *dev)
	virtio_cons.notifier_del = notifier_del_vio;		virtio_cons.notifier_del = notifier_del_vio;
	virtio_cons.notifier_hangup = 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		* The first argument of hvc_alloc() is the virtual console
	* notification mechanism (like irq number). We currently leave this		* number, so we use zero. The second argument is the
	* as zero, virtqueues have implicit notifications.		* 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()		* The third argument is a "struct hv_ops" containing the
	* get_chars(), notifier_add() and notifier_del() pointers.		* put_chars(), get_chars(), notifier_add() and notifier_del()
	* The final argument is the output buffer size: we can do any size,		* pointers. The final argument is the output buffer size: we
	* so we put PAGE_SIZE here. */		* can do any size, so we put PAGE_SIZE here.
			*/
	hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);		hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
	if (IS_ERR(hvc)) {		if (IS_ERR(hvc)) {
	err = PTR_ERR(hvc);		err = PTR_ERR(hvc);

include/linux/virtio_console.h

+4 −2

Original line number	Original line	Diff line number	Diff line
	@@ -3,8 +3,10 @@
	#include <linux/types.h>		#include <linux/types.h>
	#include <linux/virtio_ids.h>		#include <linux/virtio_ids.h>
	#include <linux/virtio_config.h>		#include <linux/virtio_config.h>
	/* This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so		/*
	* anyone can use the definitions to implement compatible drivers/servers. */		* This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so
			* anyone can use the definitions to implement compatible drivers/servers.
			*/

	/* Feature bits */		/* Feature bits */
	#define VIRTIO_CONSOLE_F_SIZE 0 /* Does host provide console size? */		#define VIRTIO_CONSOLE_F_SIZE 0 /* Does host provide console size? */