diff options
Diffstat (limited to 'drivers/char/virtio_console.c')
| -rw-r--r-- | drivers/char/virtio_console.c | 108 |
1 files changed, 54 insertions, 54 deletions
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index a035ae39a359..26e238cd7d2f 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1,18 +1,5 @@ -/*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 @@ -34,8 +21,6 @@ #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; @@ -49,12 +34,14 @@ static struct hv_ops virtio_cons; /* 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]; @@ -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 */ 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); @@ -77,8 +66,10 @@ static int put_chars(u32 vtermno, const char *buf, int 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) { struct scatterlist sg[1]; @@ -90,12 +81,14 @@ static void add_inbuf(void) 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. */ @@ -123,14 +116,16 @@ static int get_chars(u32 vtermno, char *buf, int 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 - * 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; @@ -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 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) { @@ -179,13 +174,17 @@ static void hvc_handle_input(struct virtqueue *vq) 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}; @@ -203,8 +202,6 @@ static int __devinit virtcons_probe(struct virtio_device *dev) } /* 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; @@ -219,15 +216,18 @@ static int __devinit virtcons_probe(struct virtio_device *dev) 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); |