LinuxQuestions.org - kernel driver programming

below i refer the codings but i am new to this filed even i can't understand anything from this code.i dont know where i haveto start and i want the explanation of this program what are the terms used in this and meaning of that

Linux/net/atm/ioctl.c
1 /* ATM ioctl handling */
2
3 /* Written 1995-2000 by Werner Almesberger, EPFL LRC/ICA */
4 /* 2003 John Levon <levon@movementarian.org> */
5
6 #define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
7
8 #include <linux/module.h>
9 #include <linux/kmod.h>
10 #include <linux/net.h> /* struct socket, struct proto_ops */
11 #include <linux/atm.h> /* ATM stuff */
12 #include <linux/atmdev.h>
13 #include <linux/atmclip.h> /* CLIP_*ENCAP */
14 #include <linux/atmarp.h> /* manifest constants */
15 #include <linux/capability.h>
16 #include <linux/sonet.h> /* for ioctls */
17 #include <linux/atmsvc.h>
18 #include <linux/atmmpc.h>
19 #include <net/atmclip.h>
20 #include <linux/atmlec.h>
21 #include <linux/mutex.h>
22 #include <asm/ioctls.h>
23 #include <net/compat.h>
24
25 #include "resources.h"
26 #include "signaling.h" /* for WAITING and sigd_attach */
27 #include "common.h"
28
29
30 static DEFINE_MUTEX(ioctl_mutex);
31 static LIST_HEAD(ioctl_list);
32
33
34 void register_atm_ioctl(struct atm_ioctl *ioctl)
35 {
36 mutex_lock(&ioctl_mutex);
37 list_add_tail(&ioctl->list, &ioctl_list);
38 mutex_unlock(&ioctl_mutex);
39 }
40 EXPORT_SYMBOL(register_atm_ioctl);
41
42 void deregister_atm_ioctl(struct atm_ioctl *ioctl)
43 {
44 mutex_lock(&ioctl_mutex);
45 list_del(&ioctl->list);
46 mutex_unlock(&ioctl_mutex);
47 }
48 EXPORT_SYMBOL(deregister_atm_ioctl);
49
50 static int do_vcc_ioctl(struct socket *sock, unsigned int cmd,
51 unsigned long arg, int compat)
52 {
53 struct sock *sk = sock->sk;
54 struct atm_vcc *vcc;
55 int error;
56 struct list_head *pos;
57 void __user *argp = (void __user *)arg;
58
59 vcc = ATM_SD(sock);
60 switch (cmd) {
61 case SIOCOUTQ:
62 if (sock->state != SS_CONNECTED ||
63 !test_bit(ATM_VF_READY, &vcc->flags)) {
64 error = -EINVAL;
65 goto done;
66 }
67 error = put_user(sk->sk_sndbuf - sk_wmem_alloc_get(sk),
68 (int __user *)argp) ? -EFAULT : 0;
69 goto done;
70 case SIOCINQ:
71 {
72 struct sk_buff *skb;
73
74 if (sock->state != SS_CONNECTED) {
75 error = -EINVAL;
76 goto done;
77 }
78 skb = skb_peek(&sk->sk_receive_queue);
79 error = put_user(skb ? skb->len : 0,
80 (int __user *)argp) ? -EFAULT : 0;
81 goto done;
82 }
83 case SIOCGSTAMP: /* borrowed from IP */
84 #ifdef CONFIG_COMPAT
85 if (compat)
86 error = compat_sock_get_timestamp(sk, argp);
87 else
88 #endif
89 error = sock_get_timestamp(sk, argp);
90 goto done;
91 case SIOCGSTAMPNS: /* borrowed from IP */
92 #ifdef CONFIG_COMPAT
93 if (compat)
94 error = compat_sock_get_timestampns(sk, argp);
95 else
96 #endif
97 error = sock_get_timestampns(sk, argp);
98 goto done;
99 case ATM_SETSC:
100 if (net_ratelimit())
101 pr_warning("ATM_SETSC is obsolete; used by %s:%d\n",
102 current->comm, task_pid_nr(current));
103 error = 0;
104 goto done;
105 case ATMSIGD_CTRL:
106 if (!capable(CAP_NET_ADMIN)) {
107 error = -EPERM;
108 goto done;
109 }
110 /*
111 * The user/kernel protocol for exchanging signalling
112 * info uses kernel pointers as opaque references,
113 * so the holder of the file descriptor can scribble
114 * on the kernel... so we should make sure that we
115 * have the same privileges that /proc/kcore needs
116 */
117 if (!capable(CAP_SYS_RAWIO)) {
118 error = -EPERM;
119 goto done;
120 }
121 #ifdef CONFIG_COMPAT
122 /* WTF? I don't even want to _think_ about making this
123 work for 32-bit userspace. TBH I don't really want
124 to think about it at all. dwmw2. */
125 if (compat) {
126 if (net_ratelimit())
127 pr_warning("32-bit task cannot be atmsigd\n");
128 error = -EINVAL;
129 goto done;
130 }
131 #endif
132 error = sigd_attach(vcc);
133 if (!error)
134 sock->state = SS_CONNECTED;
135 goto done;
136 case ATM_SETBACKEND:
137 case ATM_NEWBACKENDIF:
138 {
139 atm_backend_t backend;
140 error = get_user(backend, (atm_backend_t __user *)argp);
141 if (error)
142 goto done;
143 switch (backend) {
144 case ATM_BACKEND_PPP:
145 request_module("pppoatm");
146 break;
147 case ATM_BACKEND_BR2684:
148 request_module("br2684");
149 break;
150 }
151 break;
152 }
153 case ATMMPC_CTRL:
154 case ATMMPC_DATA:
155 request_module("mpoa");
156 break;
157 case ATMARPD_CTRL:
158 request_module("clip");
159 break;
160 case ATMLEC_CTRL:
161 request_module("lec");
162 break;
163 }
164
165 error = -ENOIOCTLCMD;
166
167 mutex_lock(&ioctl_mutex);
168 list_for_each(pos, &ioctl_list) {
169 struct atm_ioctl *ic = list_entry(pos, struct atm_ioctl, list);
170 if (try_module_get(ic->owner)) {
171 error = ic->ioctl(sock, cmd, arg);
172 module_put(ic->owner);
173 if (error != -ENOIOCTLCMD)
174 break;
175 }
176 }
177 mutex_unlock(&ioctl_mutex);
178
179 if (error != -ENOIOCTLCMD)
180 goto done;
181
182 error = atm_dev_ioctl(cmd, argp, compat);
183
184 done:
185 return error;
186 }
187
188 int vcc_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
189 {
190 return do_vcc_ioctl(sock, cmd, arg, 0);
191 }
192
193 #ifdef CONFIG_COMPAT
194 /*
195 * FIXME:
196 * The compat_ioctl handling is duplicated, using both these conversion
197 * routines and the compat argument to the actual handlers. Both
198 * versions are somewhat incomplete and should be merged, e.g. by
199 * moving the ioctl number translation into the actual handlers and
200 * killing the conversion code.
201 *
202 * -arnd, November 2009
203 */
204 #define ATM_GETLINKRATE32 _IOW('a', ATMIOC_ITF+1, struct compat_atmif_sioc)
205 #define ATM_GETNAMES32 _IOW('a', ATMIOC_ITF+3, struct compat_atm_iobuf)
206 #define ATM_GETTYPE32 _IOW('a', ATMIOC_ITF+4, struct compat_atmif_sioc)
207 #define ATM_GETESI32 _IOW('a', ATMIOC_ITF+5, struct compat_atmif_sioc)
208 #define ATM_GETADDR32 _IOW('a', ATMIOC_ITF+6, struct compat_atmif_sioc)
209 #define ATM_RSTADDR32 _IOW('a', ATMIOC_ITF+7, struct compat_atmif_sioc)
210 #define ATM_ADDADDR32 _IOW('a', ATMIOC_ITF+8, struct compat_atmif_sioc)
211 #define ATM_DELADDR32 _IOW('a', ATMIOC_ITF+9, struct compat_atmif_sioc)
212 #define ATM_GETCIRANGE32 _IOW('a', ATMIOC_ITF+10, struct compat_atmif_sioc)
213 #define ATM_SETCIRANGE32 _IOW('a', ATMIOC_ITF+11, struct compat_atmif_sioc)
214 #define ATM_SETESI32 _IOW('a', ATMIOC_ITF+12, struct compat_atmif_sioc)
215 #define ATM_SETESIF32 _IOW('a', ATMIOC_ITF+13, struct compat_atmif_sioc)
216 #define ATM_GETSTAT32 _IOW('a', ATMIOC_SARCOM+0, struct compat_atmif_sioc)
217 #define ATM_GETSTATZ32 _IOW('a', ATMIOC_SARCOM+1, struct compat_atmif_sioc)
218 #define ATM_GETLOOP32 _IOW('a', ATMIOC_SARCOM+2, struct compat_atmif_sioc)
219 #define ATM_SETLOOP32 _IOW('a', ATMIOC_SARCOM+3, struct compat_atmif_sioc)
220 #define ATM_QUERYLOOP32 _IOW('a', ATMIOC_SARCOM+4, struct compat_atmif_sioc)
221
222 static struct {
223 unsigned int cmd32;
224 unsigned int cmd;
225 } atm_ioctl_map[] = {
226 { ATM_GETLINKRATE32, ATM_GETLINKRATE },
227 { ATM_GETNAMES32, ATM_GETNAMES },
228 { ATM_GETTYPE32, ATM_GETTYPE },
229 { ATM_GETESI32, ATM_GETESI },
230 { ATM_GETADDR32, ATM_GETADDR },
231 { ATM_RSTADDR32, ATM_RSTADDR },
232 { ATM_ADDADDR32, ATM_ADDADDR },
233 { ATM_DELADDR32, ATM_DELADDR },
234 { ATM_GETCIRANGE32, ATM_GETCIRANGE },
235 { ATM_SETCIRANGE32, ATM_SETCIRANGE },
236 { ATM_SETESI32, ATM_SETESI },
237 { ATM_SETESIF32, ATM_SETESIF },
238 { ATM_GETSTAT32, ATM_GETSTAT },
239 { ATM_GETSTATZ32, ATM_GETSTATZ },
240 { ATM_GETLOOP32, ATM_GETLOOP },
241 { ATM_SETLOOP32, ATM_SETLOOP },
242 { ATM_QUERYLOOP32, ATM_QUERYLOOP },
243 };
244
245 #define NR_ATM_IOCTL ARRAY_SIZE(atm_ioctl_map)
246
247 static int do_atm_iobuf(struct socket *sock, unsigned int cmd,
248 unsigned long arg)
249 {
250 struct atm_iobuf __user *iobuf;
251 struct compat_atm_iobuf __user *iobuf32;
252 u32 data;
253 void __user *datap;
254 int len, err;
255
256 iobuf = compat_alloc_user_space(sizeof(*iobuf));
257 iobuf32 = compat_ptr(arg);
258
259 if (get_user(len, &iobuf32->length) ||
260 get_user(data, &iobuf32->buffer))
261 return -EFAULT;
262 datap = compat_ptr(data);
263 if (put_user(len, &iobuf->length) ||
264 put_user(datap, &iobuf->buffer))
265 return -EFAULT;
266
267 err = do_vcc_ioctl(sock, cmd, (unsigned long) iobuf, 0);
268
269 if (!err) {
270 if (copy_in_user(&iobuf32->length, &iobuf->length,
271 sizeof(int)))
272 err = -EFAULT;
273 }
274
275 return err;
276 }
277
278 static int do_atmif_sioc(struct socket *sock, unsigned int cmd,
279 unsigned long arg)
280 {
281 struct atmif_sioc __user *sioc;
282 struct compat_atmif_sioc __user *sioc32;
283 u32 data;
284 void __user *datap;
285 int err;
286
287 sioc = compat_alloc_user_space(sizeof(*sioc));
288 sioc32 = compat_ptr(arg);
289
290 if (copy_in_user(&sioc->number, &sioc32->number, 2 * sizeof(int)) ||
291 get_user(data, &sioc32->arg))
292 return -EFAULT;
293 datap = compat_ptr(data);
294 if (put_user(datap, &sioc->arg))
295 return -EFAULT;
296
297 err = do_vcc_ioctl(sock, cmd, (unsigned long) sioc, 0);
298
299 if (!err) {
300 if (copy_in_user(&sioc32->length, &sioc->length,
301 sizeof(int)))
302 err = -EFAULT;
303 }
304 return err;
305 }
306
307 static int do_atm_ioctl(struct socket *sock, unsigned int cmd32,
308 unsigned long arg)
309 {
310 int i;
311 unsigned int cmd = 0;
312
313 switch (cmd32) {
314 case SONET_GETSTAT:
315 case SONET_GETSTATZ:
316 case SONET_GETDIAG:
317 case SONET_SETDIAG:
318 case SONET_CLRDIAG:
319 case SONET_SETFRAMING:
320 case SONET_GETFRAMING:
321 case SONET_GETFRSENSE:
322 return do_atmif_sioc(sock, cmd32, arg);
323 }
324
325 for (i = 0; i < NR_ATM_IOCTL; i++) {
326 if (cmd32 == atm_ioctl_map[i].cmd32) {
327 cmd = atm_ioctl_map[i].cmd;
328 break;
329 }
330 }
331 if (i == NR_ATM_IOCTL)
332 return -EINVAL;
333
334 switch (cmd) {
335 case ATM_GETNAMES:
336 return do_atm_iobuf(sock, cmd, arg);
337
338 case ATM_GETLINKRATE:
339 case ATM_GETTYPE:
340 case ATM_GETESI:
341 case ATM_GETADDR:
342 case ATM_RSTADDR:
343 case ATM_ADDADDR:
344 case ATM_DELADDR:
345 case ATM_GETCIRANGE:
346 case ATM_SETCIRANGE:
347 case ATM_SETESI:
348 case ATM_SETESIF:
349 case ATM_GETSTAT:
350 case ATM_GETSTATZ:
351 case ATM_GETLOOP:
352 case ATM_SETLOOP:
353 case ATM_QUERYLOOP:
354 return do_atmif_sioc(sock, cmd, arg);
355 }
356
357 return -EINVAL;
358 }
359
360 int vcc_compat_ioctl(struct socket *sock, unsigned int cmd,
361 unsigned long arg)
362 {
363 int ret;
364
365 ret = do_vcc_ioctl(sock, cmd, arg, 1);
366 if (ret != -ENOIOCTLCMD)
367 return ret;
368
369 return do_atm_ioctl(sock, cmd, arg);
370 }
371 #endif
372