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 * we support only one console, the hvc struct is a global var 142 * There is no need to do anything 143 */ 144 static int notifier_add_vio(struct hvc_struct *hp, int data) 145 { 146 hp->irq_requested = 1; 147 return 0; 148 } 149 150 static void notifier_del_vio(struct hvc_struct *hp, int data) 151 { 152 hp->irq_requested = 0; 153 } 154 155 static void hvc_handle_input(struct virtqueue *vq) 156 { 157 if (hvc_poll(hvc)) 158 hvc_kick(); 159 } 160 161 /*D:370 Once we're further in boot, we get probed like any other virtio device. 162 * At this stage we set up the output virtqueue. 163 * 164 * To set up and manage our virtual console, we call hvc_alloc(). Since we 165 * never remove the console device we never need this pointer again. 166 * 167 * Finally we put our input buffer in the input queue, ready to receive. */ 168 static int __devinit virtcons_probe(struct virtio_device *dev) 169 { 170 int err; 171 172 vdev = dev; 173 174 /* This is the scratch page we use to receive console input */ 175 inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL); 176 if (!inbuf) { 177 err = -ENOMEM; 178 goto fail; 179 } 180 181 /* Find the input queue. */ 182 /* FIXME: This is why we want to wean off hvc: we do nothing 183 * when input comes in. */ 184 in_vq = vdev->config->find_vq(vdev, 0, hvc_handle_input); 185 if (IS_ERR(in_vq)) { 186 err = PTR_ERR(in_vq); 187 goto free; 188 } 189 190 out_vq = vdev->config->find_vq(vdev, 1, NULL); 191 if (IS_ERR(out_vq)) { 192 err = PTR_ERR(out_vq); 193 goto free_in_vq; 194 } 195 196 /* Start using the new console output. */ 197 virtio_cons.get_chars = get_chars; 198 virtio_cons.put_chars = put_chars; 199 virtio_cons.notifier_add = notifier_add_vio; 200 virtio_cons.notifier_del = notifier_del_vio; 201 202 /* The first argument of hvc_alloc() is the virtual console number, so 203 * we use zero. The second argument is the parameter for the 204 * notification mechanism (like irq number). We currently leave this 205 * as zero, virtqueues have implicit notifications. 206 * 207 * The third argument is a "struct hv_ops" containing the put_chars() 208 * get_chars(), notifier_add() and notifier_del() pointers. 209 * The final argument is the output buffer size: we can do any size, 210 * so we put PAGE_SIZE here. */ 211 hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE); 212 if (IS_ERR(hvc)) { 213 err = PTR_ERR(hvc); 214 goto free_out_vq; 215 } 216 217 /* Register the input buffer the first time. */ 218 add_inbuf(); 219 return 0; 220 221 free_out_vq: 222 vdev->config->del_vq(out_vq); 223 free_in_vq: 224 vdev->config->del_vq(in_vq); 225 free: 226 kfree(inbuf); 227 fail: 228 return err; 229 } 230 231 static struct virtio_device_id id_table[] = { 232 { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID }, 233 { 0 }, 234 }; 235 236 static struct virtio_driver virtio_console = { 237 .driver.name = KBUILD_MODNAME, 238 .driver.owner = THIS_MODULE, 239 .id_table = id_table, 240 .probe = virtcons_probe, 241 }; 242 243 static int __init init(void) 244 { 245 return register_virtio_driver(&virtio_console); 246 } 247 module_init(init); 248 249 MODULE_DEVICE_TABLE(virtio, id_table); 250 MODULE_DESCRIPTION("Virtio console driver"); 251 MODULE_LICENSE("GPL"); 252