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e2c97843 RR |
1 | /*D:300 |
2 | * The Guest console driver | |
3f8c4d3f | 3 | * |
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4 | * This is a trivial console driver: we use lguest's DMA mechanism to send |
5 | * bytes out, and register a DMA buffer to receive bytes in. It is assumed to | |
6 | * be present and available from the very beginning of boot. | |
7 | * | |
8 | * Writing console drivers is one of the few remaining Dark Arts in Linux. | |
9 | * Fortunately for us, the path of virtual consoles has been well-trodden by | |
10 | * the PowerPC folks, who wrote "hvc_console.c" to generically support any | |
11 | * virtual console. We use that infrastructure which only requires us to write | |
12 | * the basic put_chars and get_chars functions and call the right register | |
13 | * functions. | |
14 | :*/ | |
15 | ||
f56a384e RR |
16 | /*M:002 The console can be flooded: while the Guest is processing input the |
17 | * Host can send more. Buffering in the Host could alleviate this, but it is a | |
18 | * difficult problem in general. :*/ | |
e2c97843 | 19 | /* Copyright (C) 2006 Rusty Russell, IBM Corporation |
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20 | * |
21 | * This program is free software; you can redistribute it and/or modify | |
22 | * it under the terms of the GNU General Public License as published by | |
23 | * the Free Software Foundation; either version 2 of the License, or | |
24 | * (at your option) any later version. | |
25 | * | |
26 | * This program is distributed in the hope that it will be useful, | |
27 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
28 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
29 | * GNU General Public License for more details. | |
30 | * | |
31 | * You should have received a copy of the GNU General Public License | |
32 | * along with this program; if not, write to the Free Software | |
33 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
34 | */ | |
35 | #include <linux/err.h> | |
36 | #include <linux/init.h> | |
37 | #include <linux/lguest_bus.h> | |
38 | #include "hvc_console.h" | |
39 | ||
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40 | /*D:340 This is our single console input buffer, with associated "struct |
41 | * lguest_dma" referring to it. Note the 0-terminated length array, and the | |
42 | * use of physical address for the buffer itself. */ | |
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43 | static char inbuf[256]; |
44 | static struct lguest_dma cons_input = { .used_len = 0, | |
45 | .addr[0] = __pa(inbuf), | |
46 | .len[0] = sizeof(inbuf), | |
47 | .len[1] = 0 }; | |
48 | ||
e2c97843 RR |
49 | /*D:310 The put_chars() callback is pretty straightforward. |
50 | * | |
51 | * First we put the pointer and length in a "struct lguest_dma": we only have | |
52 | * one pointer, so we set the second length to 0. Then we use SEND_DMA to send | |
53 | * the data to (Host) buffers attached to the console key. Usually a device's | |
54 | * key is a physical address within the device's memory, but because the | |
55 | * console device doesn't have any associated physical memory, we use the | |
56 | * LGUEST_CONSOLE_DMA_KEY constant (aka 0). */ | |
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57 | static int put_chars(u32 vtermno, const char *buf, int count) |
58 | { | |
59 | struct lguest_dma dma; | |
60 | ||
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61 | /* FIXME: DMA buffers in a "struct lguest_dma" are not allowed |
62 | * to go over page boundaries. This never seems to happen, | |
63 | * but if it did we'd need to fix this code. */ | |
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64 | dma.len[0] = count; |
65 | dma.len[1] = 0; | |
66 | dma.addr[0] = __pa(buf); | |
67 | ||
68 | lguest_send_dma(LGUEST_CONSOLE_DMA_KEY, &dma); | |
e2c97843 | 69 | /* We're expected to return the amount of data we wrote: all of it. */ |
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70 | return count; |
71 | } | |
72 | ||
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73 | /*D:350 get_chars() is the callback from the hvc_console infrastructure when |
74 | * an interrupt is received. | |
75 | * | |
76 | * Firstly we see if our buffer has been filled: if not, we return. The rest | |
77 | * of the code deals with the fact that the hvc_console() infrastructure only | |
78 | * asks us for 16 bytes at a time. We keep a "cons_offset" variable for | |
79 | * partially-read buffers. */ | |
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80 | static int get_chars(u32 vtermno, char *buf, int count) |
81 | { | |
82 | static int cons_offset; | |
83 | ||
e2c97843 | 84 | /* Nothing left to see here... */ |
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85 | if (!cons_input.used_len) |
86 | return 0; | |
87 | ||
e2c97843 | 88 | /* You want more than we have to give? Well, try wanting less! */ |
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89 | if (cons_input.used_len - cons_offset < count) |
90 | count = cons_input.used_len - cons_offset; | |
91 | ||
e2c97843 | 92 | /* Copy across to their buffer and increment offset. */ |
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93 | memcpy(buf, inbuf + cons_offset, count); |
94 | cons_offset += count; | |
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95 | |
96 | /* Finished? Zero offset, and reset cons_input so Host will use it | |
97 | * again. */ | |
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98 | if (cons_offset == cons_input.used_len) { |
99 | cons_offset = 0; | |
100 | cons_input.used_len = 0; | |
101 | } | |
102 | return count; | |
103 | } | |
e2c97843 | 104 | /*:*/ |
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105 | |
106 | static struct hv_ops lguest_cons = { | |
107 | .get_chars = get_chars, | |
108 | .put_chars = put_chars, | |
109 | }; | |
110 | ||
e2c97843 RR |
111 | /*D:320 Console drivers are initialized very early so boot messages can go |
112 | * out. At this stage, the console is output-only. Our driver checks we're a | |
113 | * Guest, and if so hands hvc_instantiate() the console number (0), priority | |
114 | * (0), and the struct hv_ops containing the put_chars() function. */ | |
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115 | static int __init cons_init(void) |
116 | { | |
117 | if (strcmp(paravirt_ops.name, "lguest") != 0) | |
118 | return 0; | |
119 | ||
120 | return hvc_instantiate(0, 0, &lguest_cons); | |
121 | } | |
122 | console_initcall(cons_init); | |
123 | ||
e2c97843 RR |
124 | /*D:370 To set up and manage our virtual console, we call hvc_alloc() and |
125 | * stash the result in the private pointer of the "struct lguest_device". | |
126 | * Since we never remove the console device we never need this pointer again, | |
127 | * but using ->private is considered good form, and you never know who's going | |
128 | * to copy your driver. | |
129 | * | |
130 | * Once the console is set up, we bind our input buffer ready for input. */ | |
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131 | static int lguestcons_probe(struct lguest_device *lgdev) |
132 | { | |
133 | int err; | |
134 | ||
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135 | /* The first argument of hvc_alloc() is the virtual console number, so |
136 | * we use zero. The second argument is the interrupt number. | |
137 | * | |
138 | * The third argument is a "struct hv_ops" containing the put_chars() | |
139 | * and get_chars() pointers. The final argument is the output buffer | |
140 | * size: we use 256 and expect the Host to have room for us to send | |
141 | * that much. */ | |
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142 | lgdev->private = hvc_alloc(0, lgdev_irq(lgdev), &lguest_cons, 256); |
143 | if (IS_ERR(lgdev->private)) | |
144 | return PTR_ERR(lgdev->private); | |
145 | ||
e2c97843 RR |
146 | /* We bind a single DMA buffer at key LGUEST_CONSOLE_DMA_KEY. |
147 | * "cons_input" is that statically-initialized global DMA buffer we saw | |
148 | * above, and we also give the interrupt we want. */ | |
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149 | err = lguest_bind_dma(LGUEST_CONSOLE_DMA_KEY, &cons_input, 1, |
150 | lgdev_irq(lgdev)); | |
151 | if (err) | |
152 | printk("lguest console: failed to bind buffer.\n"); | |
153 | return err; | |
154 | } | |
e2c97843 RR |
155 | /* Note the use of lgdev_irq() for the interrupt number. We tell hvc_alloc() |
156 | * to expect input when this interrupt is triggered, and then tell | |
157 | * lguest_bind_dma() that is the interrupt to send us when input comes in. */ | |
3f8c4d3f | 158 | |
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159 | /*D:360 From now on the console driver follows standard Guest driver form: |
160 | * register_lguest_driver() registers the device type and probe function, and | |
161 | * the probe function sets up the device. | |
162 | * | |
163 | * The standard "struct lguest_driver": */ | |
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164 | static struct lguest_driver lguestcons_drv = { |
165 | .name = "lguestcons", | |
166 | .owner = THIS_MODULE, | |
167 | .device_type = LGUEST_DEVICE_T_CONSOLE, | |
168 | .probe = lguestcons_probe, | |
169 | }; | |
170 | ||
e2c97843 | 171 | /* The standard init function */ |
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172 | static int __init hvc_lguest_init(void) |
173 | { | |
174 | return register_lguest_driver(&lguestcons_drv); | |
175 | } | |
176 | module_init(hvc_lguest_init); |