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_console.h> 35 #include "hvc_console.h" 36 37 /*D:340 These represent our input and output console queues, and the virtio 38 * operations for them. */ 39 static struct virtqueue *in_vq, *out_vq; 40 static struct virtio_device *vdev; 41 42 /* This is our input buffer, and how much data is left in it. */ 43 static unsigned int in_len; 44 static char *in, *inbuf; 45 46 /* The operations for our console. */ 47 static struct hv_ops virtio_cons; 48 49 /* The hvc device */ 50 static struct hvc_struct *hvc; 51 52 /*D:310 The put_chars() callback is pretty straightforward. 53 * 54 * We turn the characters into a scatter-gather list, add it to the output 55 * queue and then kick the Host. Then we sit here waiting for it to finish: 56 * inefficient in theory, but in practice implementations will do it 57 * immediately (lguest's Launcher does). */ 58 static int put_chars(u32 vtermno, const char *buf, int count) 59 { 60 struct scatterlist sg[1]; 61 unsigned int len; 62 63 /* This is a convenient routine to initialize a single-elem sg list */ 64 sg_init_one(sg, buf, count); 65 66 /* add_buf wants a token to identify this buffer: we hand it any 67 * non-NULL pointer, since there's only ever one buffer. */ 68 if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) { 69 /* Tell Host to go! */ 70 out_vq->vq_ops->kick(out_vq); 71 /* Chill out until it's done with the buffer. */ 72 while (!out_vq->vq_ops->get_buf(out_vq, &len)) 73 cpu_relax(); 74 } 75 76 /* We're expected to return the amount of data we wrote: all of it. */ 77 return count; 78 } 79 80 /* Create a scatter-gather list representing our input buffer and put it in the 81 * queue. */ 82 static void add_inbuf(void) 83 { 84 struct scatterlist sg[1]; 85 sg_init_one(sg, inbuf, PAGE_SIZE); 86 87 /* We should always be able to add one buffer to an empty queue. */ 88 if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0) 89 BUG(); 90 in_vq->vq_ops->kick(in_vq); 91 } 92 93 /*D:350 get_chars() is the callback from the hvc_console infrastructure when 94 * an interrupt is received. 95 * 96 * Most of the code deals with the fact that the hvc_console() infrastructure 97 * only asks us for 16 bytes at a time. We keep in_offset and in_used fields 98 * for partially-filled buffers. */ 99 static int get_chars(u32 vtermno, char *buf, int count) 100 { 101 /* If we don't have an input queue yet, we can't get input. */ 102 BUG_ON(!in_vq); 103 104 /* No buffer? Try to get one. */ 105 if (!in_len) { 106 in = in_vq->vq_ops->get_buf(in_vq, &in_len); 107 if (!in) 108 return 0; 109 } 110 111 /* You want more than we have to give? Well, try wanting less! */ 112 if (in_len < count) 113 count = in_len; 114 115 /* Copy across to their buffer and increment offset. */ 116 memcpy(buf, in, count); 117 in += count; 118 in_len -= count; 119 120 /* Finished? Re-register buffer so Host will use it again. */ 121 if (in_len == 0) 122 add_inbuf(); 123 124 return count; 125 } 126 /*:*/ 127 128 /*D:320 Console drivers are initialized very early so boot messages can go out, 129 * so we do things slightly differently from the generic virtio initialization 130 * of the net and block drivers. 131 * 132 * At this stage, the console is output-only. It's too early to set up a 133 * virtqueue, so we let the drivers do some boutique early-output thing. */ 134 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int)) 135 { 136 virtio_cons.put_chars = put_chars; 137 return hvc_instantiate(0, 0, &virtio_cons); 138 } 139 140 /* 141 * virtio console configuration. This supports: 142 * - console resize 143 */ 144 static void virtcons_apply_config(struct virtio_device *dev) 145 { 146 struct winsize ws; 147 148 if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) { 149 dev->config->get(dev, 150 offsetof(struct virtio_console_config, cols), 151 &ws.ws_col, sizeof(u16)); 152 dev->config->get(dev, 153 offsetof(struct virtio_console_config, rows), 154 &ws.ws_row, sizeof(u16)); 155 hvc_resize(hvc, ws); 156 } 157 } 158 159 /* 160 * we support only one console, the hvc struct is a global var 161 * We set the configuration at this point, since we now have a tty 162 */ 163 static int notifier_add_vio(struct hvc_struct *hp, int data) 164 { 165 hp->irq_requested = 1; 166 virtcons_apply_config(vdev); 167 168 return 0; 169 } 170 171 static void notifier_del_vio(struct hvc_struct *hp, int data) 172 { 173 hp->irq_requested = 0; 174 } 175 176 static void hvc_handle_input(struct virtqueue *vq) 177 { 178 if (hvc_poll(hvc)) 179 hvc_kick(); 180 } 181 182 /*D:370 Once we're further in boot, we get probed like any other virtio device. 183 * At this stage we set up the output virtqueue. 184 * 185 * To set up and manage our virtual console, we call hvc_alloc(). Since we 186 * never remove the console device we never need this pointer again. 187 * 188 * Finally we put our input buffer in the input queue, ready to receive. */ 189 static int __devinit virtcons_probe(struct virtio_device *dev) 190 { 191 vq_callback_t *callbacks[] = { hvc_handle_input, NULL}; 192 const char *names[] = { "input", "output" }; 193 struct virtqueue *vqs[2]; 194 int err; 195 196 vdev = dev; 197 198 /* This is the scratch page we use to receive console input */ 199 inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL); 200 if (!inbuf) { 201 err = -ENOMEM; 202 goto fail; 203 } 204 205 /* Find the queues. */ 206 /* FIXME: This is why we want to wean off hvc: we do nothing 207 * when input comes in. */ 208 err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names); 209 if (err) 210 goto free; 211 212 in_vq = vqs[0]; 213 out_vq = vqs[1]; 214 215 /* Start using the new console output. */ 216 virtio_cons.get_chars = get_chars; 217 virtio_cons.put_chars = put_chars; 218 virtio_cons.notifier_add = notifier_add_vio; 219 virtio_cons.notifier_del = notifier_del_vio; 220 virtio_cons.notifier_hangup = notifier_del_vio; 221 222 /* The first argument of hvc_alloc() is the virtual console number, so 223 * we use zero. The second argument is the parameter for the 224 * notification mechanism (like irq number). We currently leave this 225 * as zero, virtqueues have implicit notifications. 226 * 227 * The third argument is a "struct hv_ops" containing the put_chars() 228 * get_chars(), notifier_add() and notifier_del() pointers. 229 * The final argument is the output buffer size: we can do any size, 230 * so we put PAGE_SIZE here. */ 231 hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE); 232 if (IS_ERR(hvc)) { 233 err = PTR_ERR(hvc); 234 goto free_vqs; 235 } 236 237 /* Register the input buffer the first time. */ 238 add_inbuf(); 239 return 0; 240 241 free_vqs: 242 vdev->config->del_vqs(vdev); 243 free: 244 kfree(inbuf); 245 fail: 246 return err; 247 } 248 249 static struct virtio_device_id id_table[] = { 250 { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID }, 251 { 0 }, 252 }; 253 254 static unsigned int features[] = { 255 VIRTIO_CONSOLE_F_SIZE, 256 }; 257 258 static struct virtio_driver virtio_console = { 259 .feature_table = features, 260 .feature_table_size = ARRAY_SIZE(features), 261 .driver.name = KBUILD_MODNAME, 262 .driver.owner = THIS_MODULE, 263 .id_table = id_table, 264 .probe = virtcons_probe, 265 .config_changed = virtcons_apply_config, 266 }; 267 268 static int __init init(void) 269 { 270 return register_virtio_driver(&virtio_console); 271 } 272 module_init(init); 273 274 MODULE_DEVICE_TABLE(virtio, id_table); 275 MODULE_DESCRIPTION("Virtio console driver"); 276 MODULE_LICENSE("GPL"); 277