1 /*D:300 2 * The Guest console driver 3 * 4 * Writing console drivers is one of the few remaining Dark Arts in Linux. 5 * Fortunately for us, the path of virtual consoles has been well-trodden by 6 * the PowerPC folks, who wrote "hvc_console.c" to generically support any 7 * virtual console. We use that infrastructure which only requires us to write 8 * the basic put_chars and get_chars functions and call the right register 9 * functions. 10 :*/ 11 12 /*M:002 The console can be flooded: while the Guest is processing input the 13 * Host can send more. Buffering in the Host could alleviate this, but it is a 14 * difficult problem in general. :*/ 15 /* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation 16 * 17 * This program is free software; you can redistribute it and/or modify 18 * it under the terms of the GNU General Public License as published by 19 * the Free Software Foundation; either version 2 of the License, or 20 * (at your option) any later version. 21 * 22 * This program is distributed in the hope that it will be useful, 23 * but WITHOUT ANY WARRANTY; without even the implied warranty of 24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 25 * GNU General Public License for more details. 26 * 27 * You should have received a copy of the GNU General Public License 28 * along with this program; if not, write to the Free Software 29 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 30 */ 31 #include <linux/err.h> 32 #include <linux/init.h> 33 #include <linux/virtio.h> 34 #include <linux/virtio_ids.h> 35 #include <linux/virtio_console.h> 36 #include "hvc_console.h" 37 38 /*D:340 These represent our input and output console queues, and the virtio 39 * operations for them. */ 40 static struct virtqueue *in_vq, *out_vq; 41 static struct virtio_device *vdev; 42 43 /* This is our input buffer, and how much data is left in it. */ 44 static unsigned int in_len; 45 static char *in, *inbuf; 46 47 /* The operations for our console. */ 48 static struct hv_ops virtio_cons; 49 50 /* The hvc device */ 51 static struct hvc_struct *hvc; 52 53 /*D:310 The put_chars() callback is pretty straightforward. 54 * 55 * We turn the characters into a scatter-gather list, add it to the output 56 * queue and then kick the Host. Then we sit here waiting for it to finish: 57 * inefficient in theory, but in practice implementations will do it 58 * immediately (lguest's Launcher does). */ 59 static int put_chars(u32 vtermno, const char *buf, int count) 60 { 61 struct scatterlist sg[1]; 62 unsigned int len; 63 64 /* This is a convenient routine to initialize a single-elem sg list */ 65 sg_init_one(sg, buf, count); 66 67 /* add_buf wants a token to identify this buffer: we hand it any 68 * non-NULL pointer, since there's only ever one buffer. */ 69 if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) >= 0) { 70 /* Tell Host to go! */ 71 out_vq->vq_ops->kick(out_vq); 72 /* Chill out until it's done with the buffer. */ 73 while (!out_vq->vq_ops->get_buf(out_vq, &len)) 74 cpu_relax(); 75 } 76 77 /* We're expected to return the amount of data we wrote: all of it. */ 78 return count; 79 } 80 81 /* Create a scatter-gather list representing our input buffer and put it in the 82 * queue. */ 83 static void add_inbuf(void) 84 { 85 struct scatterlist sg[1]; 86 sg_init_one(sg, inbuf, PAGE_SIZE); 87 88 /* We should always be able to add one buffer to an empty queue. */ 89 if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) < 0) 90 BUG(); 91 in_vq->vq_ops->kick(in_vq); 92 } 93 94 /*D:350 get_chars() is the callback from the hvc_console infrastructure when 95 * an interrupt is received. 96 * 97 * Most of the code deals with the fact that the hvc_console() infrastructure 98 * only asks us for 16 bytes at a time. We keep in_offset and in_used fields 99 * for partially-filled buffers. */ 100 static int get_chars(u32 vtermno, char *buf, int count) 101 { 102 /* If we don't have an input queue yet, we can't get input. */ 103 BUG_ON(!in_vq); 104 105 /* No buffer? Try to get one. */ 106 if (!in_len) { 107 in = in_vq->vq_ops->get_buf(in_vq, &in_len); 108 if (!in) 109 return 0; 110 } 111 112 /* You want more than we have to give? Well, try wanting less! */ 113 if (in_len < count) 114 count = in_len; 115 116 /* Copy across to their buffer and increment offset. */ 117 memcpy(buf, in, count); 118 in += count; 119 in_len -= count; 120 121 /* Finished? Re-register buffer so Host will use it again. */ 122 if (in_len == 0) 123 add_inbuf(); 124 125 return count; 126 } 127 /*:*/ 128 129 /*D:320 Console drivers are initialized very early so boot messages can go out, 130 * so we do things slightly differently from the generic virtio initialization 131 * of the net and block drivers. 132 * 133 * At this stage, the console is output-only. It's too early to set up a 134 * virtqueue, so we let the drivers do some boutique early-output thing. */ 135 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int)) 136 { 137 virtio_cons.put_chars = put_chars; 138 return hvc_instantiate(0, 0, &virtio_cons); 139 } 140 141 /* 142 * virtio console configuration. This supports: 143 * - console resize 144 */ 145 static void virtcons_apply_config(struct virtio_device *dev) 146 { 147 struct winsize ws; 148 149 if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) { 150 dev->config->get(dev, 151 offsetof(struct virtio_console_config, cols), 152 &ws.ws_col, sizeof(u16)); 153 dev->config->get(dev, 154 offsetof(struct virtio_console_config, rows), 155 &ws.ws_row, sizeof(u16)); 156 hvc_resize(hvc, ws); 157 } 158 } 159 160 /* 161 * we support only one console, the hvc struct is a global var 162 * We set the configuration at this point, since we now have a tty 163 */ 164 static int notifier_add_vio(struct hvc_struct *hp, int data) 165 { 166 hp->irq_requested = 1; 167 virtcons_apply_config(vdev); 168 169 return 0; 170 } 171 172 static void notifier_del_vio(struct hvc_struct *hp, int data) 173 { 174 hp->irq_requested = 0; 175 } 176 177 static void hvc_handle_input(struct virtqueue *vq) 178 { 179 if (hvc_poll(hvc)) 180 hvc_kick(); 181 } 182 183 /*D:370 Once we're further in boot, we get probed like any other virtio device. 184 * At this stage we set up the output virtqueue. 185 * 186 * To set up and manage our virtual console, we call hvc_alloc(). Since we 187 * never remove the console device we never need this pointer again. 188 * 189 * Finally we put our input buffer in the input queue, ready to receive. */ 190 static int __devinit virtcons_probe(struct virtio_device *dev) 191 { 192 vq_callback_t *callbacks[] = { hvc_handle_input, NULL}; 193 const char *names[] = { "input", "output" }; 194 struct virtqueue *vqs[2]; 195 int err; 196 197 vdev = dev; 198 199 /* This is the scratch page we use to receive console input */ 200 inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL); 201 if (!inbuf) { 202 err = -ENOMEM; 203 goto fail; 204 } 205 206 /* Find the queues. */ 207 /* FIXME: This is why we want to wean off hvc: we do nothing 208 * when input comes in. */ 209 err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names); 210 if (err) 211 goto free; 212 213 in_vq = vqs[0]; 214 out_vq = vqs[1]; 215 216 /* Start using the new console output. */ 217 virtio_cons.get_chars = get_chars; 218 virtio_cons.put_chars = put_chars; 219 virtio_cons.notifier_add = notifier_add_vio; 220 virtio_cons.notifier_del = notifier_del_vio; 221 virtio_cons.notifier_hangup = notifier_del_vio; 222 223 /* The first argument of hvc_alloc() is the virtual console number, so 224 * we use zero. The second argument is the parameter for the 225 * notification mechanism (like irq number). We currently leave this 226 * as zero, virtqueues have implicit notifications. 227 * 228 * The third argument is a "struct hv_ops" containing the put_chars() 229 * get_chars(), notifier_add() and notifier_del() pointers. 230 * The final argument is the output buffer size: we can do any size, 231 * so we put PAGE_SIZE here. */ 232 hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE); 233 if (IS_ERR(hvc)) { 234 err = PTR_ERR(hvc); 235 goto free_vqs; 236 } 237 238 /* Register the input buffer the first time. */ 239 add_inbuf(); 240 return 0; 241 242 free_vqs: 243 vdev->config->del_vqs(vdev); 244 free: 245 kfree(inbuf); 246 fail: 247 return err; 248 } 249 250 static struct virtio_device_id id_table[] = { 251 { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID }, 252 { 0 }, 253 }; 254 255 static unsigned int features[] = { 256 VIRTIO_CONSOLE_F_SIZE, 257 }; 258 259 static struct virtio_driver virtio_console = { 260 .feature_table = features, 261 .feature_table_size = ARRAY_SIZE(features), 262 .driver.name = KBUILD_MODNAME, 263 .driver.owner = THIS_MODULE, 264 .id_table = id_table, 265 .probe = virtcons_probe, 266 .config_changed = virtcons_apply_config, 267 }; 268 269 static int __init init(void) 270 { 271 return register_virtio_driver(&virtio_console); 272 } 273 module_init(init); 274 275 MODULE_DEVICE_TABLE(virtio, id_table); 276 MODULE_DESCRIPTION("Virtio console driver"); 277 MODULE_LICENSE("GPL"); 278