Merge branch 'pxa-devel' into pxa
[linux-2.6] / drivers / media / common / tuners / mt20xx.c
1 /*
2  * i2c tv tuner chip device driver
3  * controls microtune tuners, mt2032 + mt2050 at the moment.
4  *
5  * This "mt20xx" module was split apart from the original "tuner" module.
6  */
7 #include <linux/delay.h>
8 #include <linux/i2c.h>
9 #include <linux/videodev.h>
10 #include "tuner-i2c.h"
11 #include "mt20xx.h"
12
13 static int debug;
14 module_param(debug, int, 0644);
15 MODULE_PARM_DESC(debug, "enable verbose debug messages");
16
17 /* ---------------------------------------------------------------------- */
18
19 static unsigned int optimize_vco  = 1;
20 module_param(optimize_vco,      int, 0644);
21
22 static unsigned int tv_antenna    = 1;
23 module_param(tv_antenna,        int, 0644);
24
25 static unsigned int radio_antenna;
26 module_param(radio_antenna,     int, 0644);
27
28 /* ---------------------------------------------------------------------- */
29
30 #define MT2032 0x04
31 #define MT2030 0x06
32 #define MT2040 0x07
33 #define MT2050 0x42
34
35 static char *microtune_part[] = {
36         [ MT2030 ] = "MT2030",
37         [ MT2032 ] = "MT2032",
38         [ MT2040 ] = "MT2040",
39         [ MT2050 ] = "MT2050",
40 };
41
42 struct microtune_priv {
43         struct tuner_i2c_props i2c_props;
44
45         unsigned int xogc;
46         //unsigned int radio_if2;
47
48         u32 frequency;
49 };
50
51 static int microtune_release(struct dvb_frontend *fe)
52 {
53         kfree(fe->tuner_priv);
54         fe->tuner_priv = NULL;
55
56         return 0;
57 }
58
59 static int microtune_get_frequency(struct dvb_frontend *fe, u32 *frequency)
60 {
61         struct microtune_priv *priv = fe->tuner_priv;
62         *frequency = priv->frequency;
63         return 0;
64 }
65
66 // IsSpurInBand()?
67 static int mt2032_spurcheck(struct dvb_frontend *fe,
68                             int f1, int f2, int spectrum_from,int spectrum_to)
69 {
70         struct microtune_priv *priv = fe->tuner_priv;
71         int n1=1,n2,f;
72
73         f1=f1/1000; //scale to kHz to avoid 32bit overflows
74         f2=f2/1000;
75         spectrum_from/=1000;
76         spectrum_to/=1000;
77
78         tuner_dbg("spurcheck f1=%d f2=%d  from=%d to=%d\n",
79                   f1,f2,spectrum_from,spectrum_to);
80
81         do {
82             n2=-n1;
83             f=n1*(f1-f2);
84             do {
85                 n2--;
86                 f=f-f2;
87                 tuner_dbg("spurtest n1=%d n2=%d ftest=%d\n",n1,n2,f);
88
89                 if( (f>spectrum_from) && (f<spectrum_to))
90                         tuner_dbg("mt2032 spurcheck triggered: %d\n",n1);
91             } while ( (f>(f2-spectrum_to)) || (n2>-5));
92             n1++;
93         } while (n1<5);
94
95         return 1;
96 }
97
98 static int mt2032_compute_freq(struct dvb_frontend *fe,
99                                unsigned int rfin,
100                                unsigned int if1, unsigned int if2,
101                                unsigned int spectrum_from,
102                                unsigned int spectrum_to,
103                                unsigned char *buf,
104                                int *ret_sel,
105                                unsigned int xogc) //all in Hz
106 {
107         struct microtune_priv *priv = fe->tuner_priv;
108         unsigned int fref,lo1,lo1n,lo1a,s,sel,lo1freq, desired_lo1,
109                 desired_lo2,lo2,lo2n,lo2a,lo2num,lo2freq;
110
111         fref= 5250 *1000; //5.25MHz
112         desired_lo1=rfin+if1;
113
114         lo1=(2*(desired_lo1/1000)+(fref/1000)) / (2*fref/1000);
115         lo1n=lo1/8;
116         lo1a=lo1-(lo1n*8);
117
118         s=rfin/1000/1000+1090;
119
120         if(optimize_vco) {
121                 if(s>1890) sel=0;
122                 else if(s>1720) sel=1;
123                 else if(s>1530) sel=2;
124                 else if(s>1370) sel=3;
125                 else sel=4; // >1090
126         }
127         else {
128                 if(s>1790) sel=0; // <1958
129                 else if(s>1617) sel=1;
130                 else if(s>1449) sel=2;
131                 else if(s>1291) sel=3;
132                 else sel=4; // >1090
133         }
134         *ret_sel=sel;
135
136         lo1freq=(lo1a+8*lo1n)*fref;
137
138         tuner_dbg("mt2032: rfin=%d lo1=%d lo1n=%d lo1a=%d sel=%d, lo1freq=%d\n",
139                   rfin,lo1,lo1n,lo1a,sel,lo1freq);
140
141         desired_lo2=lo1freq-rfin-if2;
142         lo2=(desired_lo2)/fref;
143         lo2n=lo2/8;
144         lo2a=lo2-(lo2n*8);
145         lo2num=((desired_lo2/1000)%(fref/1000))* 3780/(fref/1000); //scale to fit in 32bit arith
146         lo2freq=(lo2a+8*lo2n)*fref + lo2num*(fref/1000)/3780*1000;
147
148         tuner_dbg("mt2032: rfin=%d lo2=%d lo2n=%d lo2a=%d num=%d lo2freq=%d\n",
149                   rfin,lo2,lo2n,lo2a,lo2num,lo2freq);
150
151         if(lo1a<0 || lo1a>7 || lo1n<17 ||lo1n>48 || lo2a<0 ||lo2a >7 ||lo2n<17 || lo2n>30) {
152                 tuner_info("mt2032: frequency parameters out of range: %d %d %d %d\n",
153                            lo1a, lo1n, lo2a,lo2n);
154                 return(-1);
155         }
156
157         mt2032_spurcheck(fe, lo1freq, desired_lo2,  spectrum_from, spectrum_to);
158         // should recalculate lo1 (one step up/down)
159
160         // set up MT2032 register map for transfer over i2c
161         buf[0]=lo1n-1;
162         buf[1]=lo1a | (sel<<4);
163         buf[2]=0x86; // LOGC
164         buf[3]=0x0f; //reserved
165         buf[4]=0x1f;
166         buf[5]=(lo2n-1) | (lo2a<<5);
167         if(rfin >400*1000*1000)
168                 buf[6]=0xe4;
169         else
170                 buf[6]=0xf4; // set PKEN per rev 1.2
171         buf[7]=8+xogc;
172         buf[8]=0xc3; //reserved
173         buf[9]=0x4e; //reserved
174         buf[10]=0xec; //reserved
175         buf[11]=(lo2num&0xff);
176         buf[12]=(lo2num>>8) |0x80; // Lo2RST
177
178         return 0;
179 }
180
181 static int mt2032_check_lo_lock(struct dvb_frontend *fe)
182 {
183         struct microtune_priv *priv = fe->tuner_priv;
184         int try,lock=0;
185         unsigned char buf[2];
186
187         for(try=0;try<10;try++) {
188                 buf[0]=0x0e;
189                 tuner_i2c_xfer_send(&priv->i2c_props,buf,1);
190                 tuner_i2c_xfer_recv(&priv->i2c_props,buf,1);
191                 tuner_dbg("mt2032 Reg.E=0x%02x\n",buf[0]);
192                 lock=buf[0] &0x06;
193
194                 if (lock==6)
195                         break;
196
197                 tuner_dbg("mt2032: pll wait 1ms for lock (0x%2x)\n",buf[0]);
198                 udelay(1000);
199         }
200         return lock;
201 }
202
203 static int mt2032_optimize_vco(struct dvb_frontend *fe,int sel,int lock)
204 {
205         struct microtune_priv *priv = fe->tuner_priv;
206         unsigned char buf[2];
207         int tad1;
208
209         buf[0]=0x0f;
210         tuner_i2c_xfer_send(&priv->i2c_props,buf,1);
211         tuner_i2c_xfer_recv(&priv->i2c_props,buf,1);
212         tuner_dbg("mt2032 Reg.F=0x%02x\n",buf[0]);
213         tad1=buf[0]&0x07;
214
215         if(tad1 ==0) return lock;
216         if(tad1 ==1) return lock;
217
218         if(tad1==2) {
219                 if(sel==0)
220                         return lock;
221                 else sel--;
222         }
223         else {
224                 if(sel<4)
225                         sel++;
226                 else
227                         return lock;
228         }
229
230         tuner_dbg("mt2032 optimize_vco: sel=%d\n",sel);
231
232         buf[0]=0x0f;
233         buf[1]=sel;
234         tuner_i2c_xfer_send(&priv->i2c_props,buf,2);
235         lock=mt2032_check_lo_lock(fe);
236         return lock;
237 }
238
239
240 static void mt2032_set_if_freq(struct dvb_frontend *fe, unsigned int rfin,
241                                unsigned int if1, unsigned int if2,
242                                unsigned int from, unsigned int to)
243 {
244         unsigned char buf[21];
245         int lint_try,ret,sel,lock=0;
246         struct microtune_priv *priv = fe->tuner_priv;
247
248         tuner_dbg("mt2032_set_if_freq rfin=%d if1=%d if2=%d from=%d to=%d\n",
249                   rfin,if1,if2,from,to);
250
251         buf[0]=0;
252         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,1);
253         tuner_i2c_xfer_recv(&priv->i2c_props,buf,21);
254
255         buf[0]=0;
256         ret=mt2032_compute_freq(fe,rfin,if1,if2,from,to,&buf[1],&sel,priv->xogc);
257         if (ret<0)
258                 return;
259
260         // send only the relevant registers per Rev. 1.2
261         buf[0]=0;
262         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,4);
263         buf[5]=5;
264         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf+5,4);
265         buf[11]=11;
266         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf+11,3);
267         if(ret!=3)
268                 tuner_warn("i2c i/o error: rc == %d (should be 3)\n",ret);
269
270         // wait for PLLs to lock (per manual), retry LINT if not.
271         for(lint_try=0; lint_try<2; lint_try++) {
272                 lock=mt2032_check_lo_lock(fe);
273
274                 if(optimize_vco)
275                         lock=mt2032_optimize_vco(fe,sel,lock);
276                 if(lock==6) break;
277
278                 tuner_dbg("mt2032: re-init PLLs by LINT\n");
279                 buf[0]=7;
280                 buf[1]=0x80 +8+priv->xogc; // set LINT to re-init PLLs
281                 tuner_i2c_xfer_send(&priv->i2c_props,buf,2);
282                 mdelay(10);
283                 buf[1]=8+priv->xogc;
284                 tuner_i2c_xfer_send(&priv->i2c_props,buf,2);
285         }
286
287         if (lock!=6)
288                 tuner_warn("MT2032 Fatal Error: PLLs didn't lock.\n");
289
290         buf[0]=2;
291         buf[1]=0x20; // LOGC for optimal phase noise
292         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,2);
293         if (ret!=2)
294                 tuner_warn("i2c i/o error: rc == %d (should be 2)\n",ret);
295 }
296
297
298 static int mt2032_set_tv_freq(struct dvb_frontend *fe,
299                               struct analog_parameters *params)
300 {
301         int if2,from,to;
302
303         // signal bandwidth and picture carrier
304         if (params->std & V4L2_STD_525_60) {
305                 // NTSC
306                 from = 40750*1000;
307                 to   = 46750*1000;
308                 if2  = 45750*1000;
309         } else {
310                 // PAL
311                 from = 32900*1000;
312                 to   = 39900*1000;
313                 if2  = 38900*1000;
314         }
315
316         mt2032_set_if_freq(fe, params->frequency*62500,
317                            1090*1000*1000, if2, from, to);
318
319         return 0;
320 }
321
322 static int mt2032_set_radio_freq(struct dvb_frontend *fe,
323                                  struct analog_parameters *params)
324 {
325         struct microtune_priv *priv = fe->tuner_priv;
326         int if2;
327
328         if (params->std & V4L2_STD_525_60) {
329                 tuner_dbg("pinnacle ntsc\n");
330                 if2 = 41300 * 1000;
331         } else {
332                 tuner_dbg("pinnacle pal\n");
333                 if2 = 33300 * 1000;
334         }
335
336         // per Manual for FM tuning: first if center freq. 1085 MHz
337         mt2032_set_if_freq(fe, params->frequency * 125 / 2,
338                            1085*1000*1000,if2,if2,if2);
339
340         return 0;
341 }
342
343 static int mt2032_set_params(struct dvb_frontend *fe,
344                              struct analog_parameters *params)
345 {
346         struct microtune_priv *priv = fe->tuner_priv;
347         int ret = -EINVAL;
348
349         switch (params->mode) {
350         case V4L2_TUNER_RADIO:
351                 ret = mt2032_set_radio_freq(fe, params);
352                 priv->frequency = params->frequency * 125 / 2;
353                 break;
354         case V4L2_TUNER_ANALOG_TV:
355         case V4L2_TUNER_DIGITAL_TV:
356                 ret = mt2032_set_tv_freq(fe, params);
357                 priv->frequency = params->frequency * 62500;
358                 break;
359         }
360
361         return ret;
362 }
363
364 static struct dvb_tuner_ops mt2032_tuner_ops = {
365         .set_analog_params = mt2032_set_params,
366         .release           = microtune_release,
367         .get_frequency     = microtune_get_frequency,
368 };
369
370 // Initialization as described in "MT203x Programming Procedures", Rev 1.2, Feb.2001
371 static int mt2032_init(struct dvb_frontend *fe)
372 {
373         struct microtune_priv *priv = fe->tuner_priv;
374         unsigned char buf[21];
375         int ret,xogc,xok=0;
376
377         // Initialize Registers per spec.
378         buf[1]=2; // Index to register 2
379         buf[2]=0xff;
380         buf[3]=0x0f;
381         buf[4]=0x1f;
382         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf+1,4);
383
384         buf[5]=6; // Index register 6
385         buf[6]=0xe4;
386         buf[7]=0x8f;
387         buf[8]=0xc3;
388         buf[9]=0x4e;
389         buf[10]=0xec;
390         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf+5,6);
391
392         buf[12]=13;  // Index register 13
393         buf[13]=0x32;
394         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf+12,2);
395
396         // Adjust XOGC (register 7), wait for XOK
397         xogc=7;
398         do {
399                 tuner_dbg("mt2032: xogc = 0x%02x\n",xogc&0x07);
400                 mdelay(10);
401                 buf[0]=0x0e;
402                 tuner_i2c_xfer_send(&priv->i2c_props,buf,1);
403                 tuner_i2c_xfer_recv(&priv->i2c_props,buf,1);
404                 xok=buf[0]&0x01;
405                 tuner_dbg("mt2032: xok = 0x%02x\n",xok);
406                 if (xok == 1) break;
407
408                 xogc--;
409                 tuner_dbg("mt2032: xogc = 0x%02x\n",xogc&0x07);
410                 if (xogc == 3) {
411                         xogc=4; // min. 4 per spec
412                         break;
413                 }
414                 buf[0]=0x07;
415                 buf[1]=0x88 + xogc;
416                 ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,2);
417                 if (ret!=2)
418                         tuner_warn("i2c i/o error: rc == %d (should be 2)\n",ret);
419         } while (xok != 1 );
420         priv->xogc=xogc;
421
422         memcpy(&fe->ops.tuner_ops, &mt2032_tuner_ops, sizeof(struct dvb_tuner_ops));
423
424         return(1);
425 }
426
427 static void mt2050_set_antenna(struct dvb_frontend *fe, unsigned char antenna)
428 {
429         struct microtune_priv *priv = fe->tuner_priv;
430         unsigned char buf[2];
431         int ret;
432
433         buf[0] = 6;
434         buf[1] = antenna ? 0x11 : 0x10;
435         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,2);
436         tuner_dbg("mt2050: enabled antenna connector %d\n", antenna);
437 }
438
439 static void mt2050_set_if_freq(struct dvb_frontend *fe,unsigned int freq, unsigned int if2)
440 {
441         struct microtune_priv *priv = fe->tuner_priv;
442         unsigned int if1=1218*1000*1000;
443         unsigned int f_lo1,f_lo2,lo1,lo2,f_lo1_modulo,f_lo2_modulo,num1,num2,div1a,div1b,div2a,div2b;
444         int ret;
445         unsigned char buf[6];
446
447         tuner_dbg("mt2050_set_if_freq freq=%d if1=%d if2=%d\n",
448                   freq,if1,if2);
449
450         f_lo1=freq+if1;
451         f_lo1=(f_lo1/1000000)*1000000;
452
453         f_lo2=f_lo1-freq-if2;
454         f_lo2=(f_lo2/50000)*50000;
455
456         lo1=f_lo1/4000000;
457         lo2=f_lo2/4000000;
458
459         f_lo1_modulo= f_lo1-(lo1*4000000);
460         f_lo2_modulo= f_lo2-(lo2*4000000);
461
462         num1=4*f_lo1_modulo/4000000;
463         num2=4096*(f_lo2_modulo/1000)/4000;
464
465         // todo spurchecks
466
467         div1a=(lo1/12)-1;
468         div1b=lo1-(div1a+1)*12;
469
470         div2a=(lo2/8)-1;
471         div2b=lo2-(div2a+1)*8;
472
473         if (debug > 1) {
474                 tuner_dbg("lo1 lo2 = %d %d\n", lo1, lo2);
475                 tuner_dbg("num1 num2 div1a div1b div2a div2b= %x %x %x %x %x %x\n",
476                           num1,num2,div1a,div1b,div2a,div2b);
477         }
478
479         buf[0]=1;
480         buf[1]= 4*div1b + num1;
481         if(freq<275*1000*1000) buf[1] = buf[1]|0x80;
482
483         buf[2]=div1a;
484         buf[3]=32*div2b + num2/256;
485         buf[4]=num2-(num2/256)*256;
486         buf[5]=div2a;
487         if(num2!=0) buf[5]=buf[5]|0x40;
488
489         if (debug > 1) {
490                 int i;
491                 tuner_dbg("bufs is: ");
492                 for(i=0;i<6;i++)
493                         printk("%x ",buf[i]);
494                 printk("\n");
495         }
496
497         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,6);
498         if (ret!=6)
499                 tuner_warn("i2c i/o error: rc == %d (should be 6)\n",ret);
500 }
501
502 static int mt2050_set_tv_freq(struct dvb_frontend *fe,
503                               struct analog_parameters *params)
504 {
505         unsigned int if2;
506
507         if (params->std & V4L2_STD_525_60) {
508                 // NTSC
509                 if2 = 45750*1000;
510         } else {
511                 // PAL
512                 if2 = 38900*1000;
513         }
514         if (V4L2_TUNER_DIGITAL_TV == params->mode) {
515                 // DVB (pinnacle 300i)
516                 if2 = 36150*1000;
517         }
518         mt2050_set_if_freq(fe, params->frequency*62500, if2);
519         mt2050_set_antenna(fe, tv_antenna);
520
521         return 0;
522 }
523
524 static int mt2050_set_radio_freq(struct dvb_frontend *fe,
525                                  struct analog_parameters *params)
526 {
527         struct microtune_priv *priv = fe->tuner_priv;
528         int if2;
529
530         if (params->std & V4L2_STD_525_60) {
531                 tuner_dbg("pinnacle ntsc\n");
532                 if2 = 41300 * 1000;
533         } else {
534                 tuner_dbg("pinnacle pal\n");
535                 if2 = 33300 * 1000;
536         }
537
538         mt2050_set_if_freq(fe, params->frequency * 125 / 2, if2);
539         mt2050_set_antenna(fe, radio_antenna);
540
541         return 0;
542 }
543
544 static int mt2050_set_params(struct dvb_frontend *fe,
545                              struct analog_parameters *params)
546 {
547         struct microtune_priv *priv = fe->tuner_priv;
548         int ret = -EINVAL;
549
550         switch (params->mode) {
551         case V4L2_TUNER_RADIO:
552                 ret = mt2050_set_radio_freq(fe, params);
553                 priv->frequency = params->frequency * 125 / 2;
554                 break;
555         case V4L2_TUNER_ANALOG_TV:
556         case V4L2_TUNER_DIGITAL_TV:
557                 ret = mt2050_set_tv_freq(fe, params);
558                 priv->frequency = params->frequency * 62500;
559                 break;
560         }
561
562         return ret;
563 }
564
565 static struct dvb_tuner_ops mt2050_tuner_ops = {
566         .set_analog_params = mt2050_set_params,
567         .release           = microtune_release,
568         .get_frequency     = microtune_get_frequency,
569 };
570
571 static int mt2050_init(struct dvb_frontend *fe)
572 {
573         struct microtune_priv *priv = fe->tuner_priv;
574         unsigned char buf[2];
575         int ret;
576
577         buf[0]=6;
578         buf[1]=0x10;
579         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,2); //  power
580
581         buf[0]=0x0f;
582         buf[1]=0x0f;
583         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,2); // m1lo
584
585         buf[0]=0x0d;
586         ret=tuner_i2c_xfer_send(&priv->i2c_props,buf,1);
587         tuner_i2c_xfer_recv(&priv->i2c_props,buf,1);
588
589         tuner_dbg("mt2050: sro is %x\n",buf[0]);
590
591         memcpy(&fe->ops.tuner_ops, &mt2050_tuner_ops, sizeof(struct dvb_tuner_ops));
592
593         return 0;
594 }
595
596 struct dvb_frontend *microtune_attach(struct dvb_frontend *fe,
597                                       struct i2c_adapter* i2c_adap,
598                                       u8 i2c_addr)
599 {
600         struct microtune_priv *priv = NULL;
601         char *name;
602         unsigned char buf[21];
603         int company_code;
604
605         priv = kzalloc(sizeof(struct microtune_priv), GFP_KERNEL);
606         if (priv == NULL)
607                 return NULL;
608         fe->tuner_priv = priv;
609
610         priv->i2c_props.addr = i2c_addr;
611         priv->i2c_props.adap = i2c_adap;
612         priv->i2c_props.name = "mt20xx";
613
614         //priv->radio_if2 = 10700 * 1000;       /* 10.7MHz - FM radio */
615
616         memset(buf,0,sizeof(buf));
617
618         name = "unknown";
619
620         tuner_i2c_xfer_send(&priv->i2c_props,buf,1);
621         tuner_i2c_xfer_recv(&priv->i2c_props,buf,21);
622         if (debug) {
623                 int i;
624                 tuner_dbg("MT20xx hexdump:");
625                 for(i=0;i<21;i++) {
626                         printk(" %02x",buf[i]);
627                         if(((i+1)%8)==0) printk(" ");
628                 }
629                 printk("\n");
630         }
631         company_code = buf[0x11] << 8 | buf[0x12];
632         tuner_info("microtune: companycode=%04x part=%02x rev=%02x\n",
633                    company_code,buf[0x13],buf[0x14]);
634
635
636         if (buf[0x13] < ARRAY_SIZE(microtune_part) &&
637             NULL != microtune_part[buf[0x13]])
638                 name = microtune_part[buf[0x13]];
639         switch (buf[0x13]) {
640         case MT2032:
641                 mt2032_init(fe);
642                 break;
643         case MT2050:
644                 mt2050_init(fe);
645                 break;
646         default:
647                 tuner_info("microtune %s found, not (yet?) supported, sorry :-/\n",
648                            name);
649                 return NULL;
650         }
651
652         strlcpy(fe->ops.tuner_ops.info.name, name,
653                 sizeof(fe->ops.tuner_ops.info.name));
654         tuner_info("microtune %s found, OK\n",name);
655         return fe;
656 }
657
658 EXPORT_SYMBOL_GPL(microtune_attach);
659
660 MODULE_DESCRIPTION("Microtune tuner driver");
661 MODULE_AUTHOR("Ralph Metzler, Gerd Knorr, Gunther Mayer");
662 MODULE_LICENSE("GPL");
663
664 /*
665  * Overrides for Emacs so that we follow Linus's tabbing style.
666  * ---------------------------------------------------------------------------
667  * Local variables:
668  * c-basic-offset: 8
669  * End:
670  */