xref: /netbsd-src/sys/modules/examples/luareadhappy/luareadhappy.c (revision 67a548a800ad4f222e634c43037f2f08f1cde4bf)
1 /*	$NetBSD: luareadhappy.c,v 1.2 2020/01/30 07:58:33 kamil Exp $	*/
2 
3 /*-
4  * Copyright (c) 2015 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26  * POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 __KERNEL_RCSID(0, "$NetBSD: luareadhappy.c,v 1.2 2020/01/30 07:58:33 kamil Exp $");
31 
32 #include <sys/param.h>
33 #include <sys/conf.h>
34 #include <sys/device.h>
35 #include <sys/kernel.h>
36 #include <sys/lua.h>
37 #include <sys/module.h>
38 #include <lua.h>
39 
40 /*
41  * Create a device /dev/happy from which you can read sequential
42  * happy numbers.
43  *
44  * To use this device you need to do:
45  *     mknod /dev/happy c 351 0
46  *
47  * Commentary:
48  * A happy number is a number defined by the following process: Starting with
49  * any positive integer, replace the number by the sum of the squares of its
50  * digits, and repeat the process until the number equals 1 (where it will
51  * stay), or it loops endlessly in a cycle which does not include 1. Those
52  * numbers for which this process ends in 1 are happy numbers, while those that
53  * do not end in 1 are unhappy numbers (or sad numbers).
54  *
55  * For more information on happy numbers, and the algorithms, see
56  *	http://en.wikipedia.org/wiki/Happy_number
57  *
58  * The happy number generator is here only to have something that the user
59  * can read from our device.  Any other arbitrary data generator could
60  * have been used.  The algorithm is not critical to the implementation
61  * of the module.
62  */
63 
64 dev_type_open(happy_open);
65 dev_type_close(happy_close);
66 dev_type_read(happy_read);
67 
68 static struct cdevsw happy_cdevsw = {
69 	.d_open = happy_open,
70 	.d_close = happy_close,
71 	.d_read = happy_read,
72 	.d_write = nowrite,
73 	.d_ioctl = noioctl,
74 	.d_stop = nostop,
75 	.d_tty = notty,
76 	.d_poll = nopoll,
77 	.d_mmap = nommap,
78 	.d_kqfilter = nokqfilter,
79 	.d_discard = nodiscard,
80 	.d_flag = D_OTHER
81 };
82 
83 
84 struct happy_softc {
85 	int		 refcnt;
86 	unsigned	 last;
87 	klua_State	*kL;
88 };
89 
90 static struct happy_softc sc;
91 
92 /* Function that calls a Lua routine and returns whether a number is happy */
93 static int
check_happy(unsigned n)94 check_happy(unsigned n)
95 {
96 	int rv;
97 
98 	klua_lock(sc.kL);
99 	lua_getglobal(sc.kL->L, "is_happy");
100 
101         if (!lua_isfunction(sc.kL->L, -1)) {
102 		lua_pop(sc.kL->L, 1);
103 		klua_unlock(sc.kL);
104 		return -1;
105         }
106 
107         lua_pushnumber(sc.kL->L, n);
108         if (lua_pcall(sc.kL->L, 1 /* args */, 1 /* res */, 0) != 0) {
109 		lua_pop(sc.kL->L, 2);
110 		klua_unlock(sc.kL);
111 		return -1;
112         }
113 
114         if (!lua_isnumber(sc.kL->L, -1)) {
115 		lua_pop(sc.kL->L, 1);
116 		klua_unlock(sc.kL);
117 		return -1;
118         }
119 
120         rv = lua_tointeger(sc.kL->L, -1);
121 
122         lua_pop(sc.kL->L, 1);
123         klua_unlock(sc.kL);
124 
125 	/* Consistency check */
126 	if (rv != 0 && rv != 1)
127 		rv = -1;
128 
129 	return rv;
130 }
131 
132 int
happy_open(dev_t self __unused,int flag __unused,int mode __unused,struct lwp * l __unused)133 happy_open(dev_t self __unused, int flag __unused, int mode __unused,
134            struct lwp *l __unused)
135 {
136 	if (sc.refcnt > 0)
137 		return EBUSY;
138 
139 	sc.last = 0;
140 	++sc.refcnt;
141 
142 	return 0;
143 }
144 
145 int
happy_close(dev_t self __unused,int flag __unused,int mode __unused,struct lwp * l __unused)146 happy_close(dev_t self __unused, int flag __unused, int mode __unused,
147             struct lwp *l __unused)
148 {
149 	--sc.refcnt;
150 
151 	return 0;
152 }
153 
154 int
happy_read(dev_t self __unused,struct uio * uio,int flags __unused)155 happy_read(dev_t self __unused, struct uio *uio, int flags __unused)
156 {
157 	int rv;
158 	char line[80];
159 
160 	/* Get next happy number */
161 	while ((rv = check_happy(++sc.last)) == 0)
162 		continue;
163 
164 	/* Something went wrong */
165 	if (rv == -1)
166 		return ECANCELED;
167 
168 	/* Print it into line[] with trailing \n */
169 	int len = snprintf(line, sizeof(line), "%u\n", sc.last);
170 
171 	/* Is there room? */
172 	if (uio->uio_resid < len) {
173 		--sc.last; /* Step back */
174 		return EINVAL;
175 	}
176 
177 	/* Send it to User-Space */
178 	int e;
179 	if ((e = uiomove(line, len, uio)))
180 		return e;
181 
182 	return 0;
183 }
184 
185 MODULE(MODULE_CLASS_MISC, happy, "lua");
186 
187 static int
happy_modcmd(modcmd_t cmd,void * arg __unused)188 happy_modcmd(modcmd_t cmd, void *arg __unused)
189 {
190 	/* The major should be verified and changed if needed to avoid
191 	 * conflicts with other devices. */
192 	int cmajor = 351, bmajor = -1;
193 
194 	switch (cmd) {
195 	case MODULE_CMD_INIT:
196 		if (devsw_attach("happy", NULL, &bmajor, &happy_cdevsw,
197 		                 &cmajor))
198 			return ENXIO;
199 		if ((sc.kL = kluaL_newstate("happy",
200 		                            "Example Happy Number calculator",
201 		                            IPL_NONE)) == NULL) {
202 			devsw_detach(NULL, &happy_cdevsw);
203 			return ENXIO;
204 		}
205 		return 0;
206 	case MODULE_CMD_FINI:
207 		if (sc.refcnt > 0)
208 			return EBUSY;
209 
210 		klua_close(sc.kL);
211 
212 		devsw_detach(NULL, &happy_cdevsw);
213 		return 0;
214 	default:
215 		return ENOTTY;
216 	}
217 }
218