drivers/media/platform/vivid/vivid-sdr-cap.c

   1 /*
   2  * vivid-sdr-cap.c - software defined radio support functions.
   3  *
   4  * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
   5  *
   6  * This program is free software; you may redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; version 2 of the License.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  11  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  12  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  13  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  14  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  15  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  16  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  17  * SOFTWARE.
  18  */
  19
  20 #include <linux/errno.h>
  21 #include <linux/kernel.h>
  22 #include <linux/delay.h>
  23 #include <linux/kthread.h>
  24 #include <linux/freezer.h>
  25 #include <linux/math64.h>
  26 #include <linux/videodev2.h>
  27 #include <linux/v4l2-dv-timings.h>
  28 #include <media/v4l2-common.h>
  29 #include <media/v4l2-event.h>
  30 #include <media/v4l2-dv-timings.h>
  31 #include <linux/fixp-arith.h>
  32
  33 #include "vivid-core.h"
  34 #include "vivid-ctrls.h"
  35 #include "vivid-sdr-cap.h"
  36
  37 /* stream formats */
  38 struct vivid_format {
  39         u32     pixelformat;
  40         u32     buffersize;
  41 };
  42
  43 /* format descriptions for capture and preview */
  44 static const struct vivid_format formats[] = {
  45         {
  46                 .pixelformat    = V4L2_SDR_FMT_CU8,
  47                 .buffersize     = SDR_CAP_SAMPLES_PER_BUF * 2,
  48         }, {
  49                 .pixelformat    = V4L2_SDR_FMT_CS8,
  50                 .buffersize     = SDR_CAP_SAMPLES_PER_BUF * 2,
  51         },
  52 };
  53
  54 static const struct v4l2_frequency_band bands_adc[] = {
  55         {
  56                 .tuner = 0,
  57                 .type = V4L2_TUNER_ADC,
  58                 .index = 0,
  59                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  60                 .rangelow   =  300000,
  61                 .rangehigh  =  300000,
  62         },
  63         {
  64                 .tuner = 0,
  65                 .type = V4L2_TUNER_ADC,
  66                 .index = 1,
  67                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  68                 .rangelow   =  900001,
  69                 .rangehigh  = 2800000,
  70         },
  71         {
  72                 .tuner = 0,
  73                 .type = V4L2_TUNER_ADC,
  74                 .index = 2,
  75                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  76                 .rangelow   = 3200000,
  77                 .rangehigh  = 3200000,
  78         },
  79 };
  80
  81 /* ADC band midpoints */
  82 #define BAND_ADC_0 ((bands_adc[0].rangehigh + bands_adc[1].rangelow) / 2)
  83 #define BAND_ADC_1 ((bands_adc[1].rangehigh + bands_adc[2].rangelow) / 2)
  84
  85 static const struct v4l2_frequency_band bands_fm[] = {
  86         {
  87                 .tuner = 1,
  88                 .type = V4L2_TUNER_RF,
  89                 .index = 0,
  90                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  91                 .rangelow   =    50000000,
  92                 .rangehigh  =  2000000000,
  93         },
  94 };
  95
  96 static void vivid_thread_sdr_cap_tick(struct vivid_dev *dev)
  97 {
  98         struct vivid_buffer *sdr_cap_buf = NULL;
  99
 100         dprintk(dev, 1, "SDR Capture Thread Tick\n");
 101
 102         /* Drop a certain percentage of buffers. */
 103         if (dev->perc_dropped_buffers &&
 104             prandom_u32_max(100) < dev->perc_dropped_buffers)
 105                 return;
 106
 107         spin_lock(&dev->slock);
 108         if (!list_empty(&dev->sdr_cap_active)) {
 109                 sdr_cap_buf = list_entry(dev->sdr_cap_active.next,
 110                                          struct vivid_buffer, list);
 111                 list_del(&sdr_cap_buf->list);
 112         }
 113         spin_unlock(&dev->slock);
 114
 115         if (sdr_cap_buf) {
 116                 sdr_cap_buf->vb.sequence = dev->sdr_cap_seq_count;
 117                 vivid_sdr_cap_process(dev, sdr_cap_buf);
 118                 sdr_cap_buf->vb.vb2_buf.timestamp =
 119                         ktime_get_ns() + dev->time_wrap_offset;
 120                 vb2_buffer_done(&sdr_cap_buf->vb.vb2_buf, dev->dqbuf_error ?
 121                                 VB2_BUF_STATE_ERROR : VB2_BUF_STATE_DONE);
 122                 dev->dqbuf_error = false;
 123         }
 124 }
 125
 126 static int vivid_thread_sdr_cap(void *data)
 127 {
 128         struct vivid_dev *dev = data;
 129         u64 samples_since_start;
 130         u64 buffers_since_start;
 131         u64 next_jiffies_since_start;
 132         unsigned long jiffies_since_start;
 133         unsigned long cur_jiffies;
 134         unsigned wait_jiffies;
 135
 136         dprintk(dev, 1, "SDR Capture Thread Start\n");
 137
 138         set_freezable();
 139
 140         /* Resets frame counters */
 141         dev->sdr_cap_seq_offset = 0;
 142         if (dev->seq_wrap)
 143                 dev->sdr_cap_seq_offset = 0xffffff80U;
 144         dev->jiffies_sdr_cap = jiffies;
 145         dev->sdr_cap_seq_resync = false;
 146
 147         for (;;) {
 148                 try_to_freeze();
 149                 if (kthread_should_stop())
 150                         break;
 151
 152                 mutex_lock(&dev->mutex);
 153                 cur_jiffies = jiffies;
 154                 if (dev->sdr_cap_seq_resync) {
 155                         dev->jiffies_sdr_cap = cur_jiffies;
 156                         dev->sdr_cap_seq_offset = dev->sdr_cap_seq_count + 1;
 157                         dev->sdr_cap_seq_count = 0;
 158                         dev->sdr_cap_seq_resync = false;
 159                 }
 160                 /* Calculate the number of jiffies since we started streaming */
 161                 jiffies_since_start = cur_jiffies - dev->jiffies_sdr_cap;
 162                 /* Get the number of buffers streamed since the start */
 163                 buffers_since_start =
 164                         (u64)jiffies_since_start * dev->sdr_adc_freq +
 165                                       (HZ * SDR_CAP_SAMPLES_PER_BUF) / 2;
 166                 do_div(buffers_since_start, HZ * SDR_CAP_SAMPLES_PER_BUF);
 167
 168                 /*
 169                  * After more than 0xf0000000 (rounded down to a multiple of
 170                  * 'jiffies-per-day' to ease jiffies_to_msecs calculation)
 171                  * jiffies have passed since we started streaming reset the
 172                  * counters and keep track of the sequence offset.
 173                  */
 174                 if (jiffies_since_start > JIFFIES_RESYNC) {
 175                         dev->jiffies_sdr_cap = cur_jiffies;
 176                         dev->sdr_cap_seq_offset = buffers_since_start;
 177                         buffers_since_start = 0;
 178                 }
 179                 dev->sdr_cap_seq_count =
 180                         buffers_since_start + dev->sdr_cap_seq_offset;
 181
 182                 vivid_thread_sdr_cap_tick(dev);
 183                 mutex_unlock(&dev->mutex);
 184
 185                 /*
 186                  * Calculate the number of samples streamed since we started,
 187                  * not including the current buffer.
 188                  */
 189                 samples_since_start = buffers_since_start * SDR_CAP_SAMPLES_PER_BUF;
 190
 191                 /* And the number of jiffies since we started */
 192                 jiffies_since_start = jiffies - dev->jiffies_sdr_cap;
 193
 194                 /* Increase by the number of samples in one buffer */
 195                 samples_since_start += SDR_CAP_SAMPLES_PER_BUF;
 196                 /*
 197                  * Calculate when that next buffer is supposed to start
 198                  * in jiffies since we started streaming.
 199                  */
 200                 next_jiffies_since_start = samples_since_start * HZ +
 201                                            dev->sdr_adc_freq / 2;
 202                 do_div(next_jiffies_since_start, dev->sdr_adc_freq);
 203                 /* If it is in the past, then just schedule asap */
 204                 if (next_jiffies_since_start < jiffies_since_start)
 205                         next_jiffies_since_start = jiffies_since_start;
 206
 207                 wait_jiffies = next_jiffies_since_start - jiffies_since_start;
 208                 schedule_timeout_interruptible(wait_jiffies ? wait_jiffies : 1);
 209         }
 210         dprintk(dev, 1, "SDR Capture Thread End\n");
 211         return 0;
 212 }
 213
 214 static int sdr_cap_queue_setup(struct vb2_queue *vq,
 215                        unsigned *nbuffers, unsigned *nplanes,
 216                        unsigned sizes[], void *alloc_ctxs[])
 217 {
 218         /* 2 = max 16-bit sample returned */
 219         sizes[0] = SDR_CAP_SAMPLES_PER_BUF * 2;
 220         *nplanes = 1;
 221         return 0;
 222 }
 223
 224 static int sdr_cap_buf_prepare(struct vb2_buffer *vb)
 225 {
 226         struct vivid_dev *dev = vb2_get_drv_priv(vb->vb2_queue);
 227         unsigned size = SDR_CAP_SAMPLES_PER_BUF * 2;
 228
 229         dprintk(dev, 1, "%s\n", __func__);
 230
 231         if (dev->buf_prepare_error) {
 232                 /*
 233                  * Error injection: test what happens if buf_prepare() returns
 234                  * an error.
 235                  */
 236                 dev->buf_prepare_error = false;
 237                 return -EINVAL;
 238         }
 239         if (vb2_plane_size(vb, 0) < size) {
 240                 dprintk(dev, 1, "%s data will not fit into plane (%lu < %u)\n",
 241                                 __func__, vb2_plane_size(vb, 0), size);
 242                 return -EINVAL;
 243         }
 244         vb2_set_plane_payload(vb, 0, size);
 245
 246         return 0;
 247 }
 248
 249 static void sdr_cap_buf_queue(struct vb2_buffer *vb)
 250 {
 251         struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
 252         struct vivid_dev *dev = vb2_get_drv_priv(vb->vb2_queue);
 253         struct vivid_buffer *buf = container_of(vbuf, struct vivid_buffer, vb);
 254
 255         dprintk(dev, 1, "%s\n", __func__);
 256
 257         spin_lock(&dev->slock);
 258         list_add_tail(&buf->list, &dev->sdr_cap_active);
 259         spin_unlock(&dev->slock);
 260 }
 261
 262 static int sdr_cap_start_streaming(struct vb2_queue *vq, unsigned count)
 263 {
 264         struct vivid_dev *dev = vb2_get_drv_priv(vq);
 265         int err = 0;
 266
 267         dprintk(dev, 1, "%s\n", __func__);
 268         dev->sdr_cap_seq_count = 0;
 269         if (dev->start_streaming_error) {
 270                 dev->start_streaming_error = false;
 271                 err = -EINVAL;
 272         } else if (dev->kthread_sdr_cap == NULL) {
 273                 dev->kthread_sdr_cap = kthread_run(vivid_thread_sdr_cap, dev,
 274                                 "%s-sdr-cap", dev->v4l2_dev.name);
 275
 276                 if (IS_ERR(dev->kthread_sdr_cap)) {
 277                         v4l2_err(&dev->v4l2_dev, "kernel_thread() failed\n");
 278                         err = PTR_ERR(dev->kthread_sdr_cap);
 279                         dev->kthread_sdr_cap = NULL;
 280                 }
 281         }
 282         if (err) {
 283                 struct vivid_buffer *buf, *tmp;
 284
 285                 list_for_each_entry_safe(buf, tmp, &dev->sdr_cap_active, list) {
 286                         list_del(&buf->list);
 287                         vb2_buffer_done(&buf->vb.vb2_buf,
 288                                         VB2_BUF_STATE_QUEUED);
 289                 }
 290         }
 291         return err;
 292 }
 293
 294 /* abort streaming and wait for last buffer */
 295 static void sdr_cap_stop_streaming(struct vb2_queue *vq)
 296 {
 297         struct vivid_dev *dev = vb2_get_drv_priv(vq);
 298
 299         if (dev->kthread_sdr_cap == NULL)
 300                 return;
 301
 302         while (!list_empty(&dev->sdr_cap_active)) {
 303                 struct vivid_buffer *buf;
 304
 305                 buf = list_entry(dev->sdr_cap_active.next,
 306                                 struct vivid_buffer, list);
 307                 list_del(&buf->list);
 308                 vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
 309         }
 310
 311         /* shutdown control thread */
 312         mutex_unlock(&dev->mutex);
 313         kthread_stop(dev->kthread_sdr_cap);
 314         dev->kthread_sdr_cap = NULL;
 315         mutex_lock(&dev->mutex);
 316 }
 317
 318 const struct vb2_ops vivid_sdr_cap_qops = {
 319         .queue_setup            = sdr_cap_queue_setup,
 320         .buf_prepare            = sdr_cap_buf_prepare,
 321         .buf_queue              = sdr_cap_buf_queue,
 322         .start_streaming        = sdr_cap_start_streaming,
 323         .stop_streaming         = sdr_cap_stop_streaming,
 324         .wait_prepare           = vb2_ops_wait_prepare,
 325         .wait_finish            = vb2_ops_wait_finish,
 326 };
 327
 328 int vivid_sdr_enum_freq_bands(struct file *file, void *fh,
 329                 struct v4l2_frequency_band *band)
 330 {
 331         switch (band->tuner) {
 332         case 0:
 333                 if (band->index >= ARRAY_SIZE(bands_adc))
 334                         return -EINVAL;
 335                 *band = bands_adc[band->index];
 336                 return 0;
 337         case 1:
 338                 if (band->index >= ARRAY_SIZE(bands_fm))
 339                         return -EINVAL;
 340                 *band = bands_fm[band->index];
 341                 return 0;
 342         default:
 343                 return -EINVAL;
 344         }
 345 }
 346
 347 int vivid_sdr_g_frequency(struct file *file, void *fh,
 348                 struct v4l2_frequency *vf)
 349 {
 350         struct vivid_dev *dev = video_drvdata(file);
 351
 352         switch (vf->tuner) {
 353         case 0:
 354                 vf->frequency = dev->sdr_adc_freq;
 355                 vf->type = V4L2_TUNER_ADC;
 356                 return 0;
 357         case 1:
 358                 vf->frequency = dev->sdr_fm_freq;
 359                 vf->type = V4L2_TUNER_RF;
 360                 return 0;
 361         default:
 362                 return -EINVAL;
 363         }
 364 }
 365
 366 int vivid_sdr_s_frequency(struct file *file, void *fh,
 367                 const struct v4l2_frequency *vf)
 368 {
 369         struct vivid_dev *dev = video_drvdata(file);
 370         unsigned freq = vf->frequency;
 371         unsigned band;
 372
 373         switch (vf->tuner) {
 374         case 0:
 375                 if (vf->type != V4L2_TUNER_ADC)
 376                         return -EINVAL;
 377                 if (freq < BAND_ADC_0)
 378                         band = 0;
 379                 else if (freq < BAND_ADC_1)
 380                         band = 1;
 381                 else
 382                         band = 2;
 383
 384                 freq = clamp_t(unsigned, freq,
 385                                 bands_adc[band].rangelow,
 386                                 bands_adc[band].rangehigh);
 387
 388                 if (vb2_is_streaming(&dev->vb_sdr_cap_q) &&
 389                     freq != dev->sdr_adc_freq) {
 390                         /* resync the thread's timings */
 391                         dev->sdr_cap_seq_resync = true;
 392                 }
 393                 dev->sdr_adc_freq = freq;
 394                 return 0;
 395         case 1:
 396                 if (vf->type != V4L2_TUNER_RF)
 397                         return -EINVAL;
 398                 dev->sdr_fm_freq = clamp_t(unsigned, freq,
 399                                 bands_fm[0].rangelow,
 400                                 bands_fm[0].rangehigh);
 401                 return 0;
 402         default:
 403                 return -EINVAL;
 404         }
 405 }
 406
 407 int vivid_sdr_g_tuner(struct file *file, void *fh, struct v4l2_tuner *vt)
 408 {
 409         switch (vt->index) {
 410         case 0:
 411                 strlcpy(vt->name, "ADC", sizeof(vt->name));
 412                 vt->type = V4L2_TUNER_ADC;
 413                 vt->capability =
 414                         V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS;
 415                 vt->rangelow = bands_adc[0].rangelow;
 416                 vt->rangehigh = bands_adc[2].rangehigh;
 417                 return 0;
 418         case 1:
 419                 strlcpy(vt->name, "RF", sizeof(vt->name));
 420                 vt->type = V4L2_TUNER_RF;
 421                 vt->capability =
 422                         V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS;
 423                 vt->rangelow = bands_fm[0].rangelow;
 424                 vt->rangehigh = bands_fm[0].rangehigh;
 425                 return 0;
 426         default:
 427                 return -EINVAL;
 428         }
 429 }
 430
 431 int vivid_sdr_s_tuner(struct file *file, void *fh, const struct v4l2_tuner *vt)
 432 {
 433         if (vt->index > 1)
 434                 return -EINVAL;
 435         return 0;
 436 }
 437
 438 int vidioc_enum_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_fmtdesc *f)
 439 {
 440         if (f->index >= ARRAY_SIZE(formats))
 441                 return -EINVAL;
 442         f->pixelformat = formats[f->index].pixelformat;
 443         return 0;
 444 }
 445
 446 int vidioc_g_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
 447 {
 448         struct vivid_dev *dev = video_drvdata(file);
 449
 450         f->fmt.sdr.pixelformat = dev->sdr_pixelformat;
 451         f->fmt.sdr.buffersize = dev->sdr_buffersize;
 452         memset(f->fmt.sdr.reserved, 0, sizeof(f->fmt.sdr.reserved));
 453         return 0;
 454 }
 455
 456 int vidioc_s_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
 457 {
 458         struct vivid_dev *dev = video_drvdata(file);
 459         struct vb2_queue *q = &dev->vb_sdr_cap_q;
 460         int i;
 461
 462         if (vb2_is_busy(q))
 463                 return -EBUSY;
 464
 465         memset(f->fmt.sdr.reserved, 0, sizeof(f->fmt.sdr.reserved));
 466         for (i = 0; i < ARRAY_SIZE(formats); i++) {
 467                 if (formats[i].pixelformat == f->fmt.sdr.pixelformat) {
 468                         dev->sdr_pixelformat = formats[i].pixelformat;
 469                         dev->sdr_buffersize = formats[i].buffersize;
 470                         f->fmt.sdr.buffersize = formats[i].buffersize;
 471                         return 0;
 472                 }
 473         }
 474         dev->sdr_pixelformat = formats[0].pixelformat;
 475         dev->sdr_buffersize = formats[0].buffersize;
 476         f->fmt.sdr.pixelformat = formats[0].pixelformat;
 477         f->fmt.sdr.buffersize = formats[0].buffersize;
 478         return 0;
 479 }
 480
 481 int vidioc_try_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
 482 {
 483         int i;
 484
 485         memset(f->fmt.sdr.reserved, 0, sizeof(f->fmt.sdr.reserved));
 486         for (i = 0; i < ARRAY_SIZE(formats); i++) {
 487                 if (formats[i].pixelformat == f->fmt.sdr.pixelformat) {
 488                         f->fmt.sdr.buffersize = formats[i].buffersize;
 489                         return 0;
 490                 }
 491         }
 492         f->fmt.sdr.pixelformat = formats[0].pixelformat;
 493         f->fmt.sdr.buffersize = formats[0].buffersize;
 494         return 0;
 495 }
 496
 497 #define FIXP_N    (15)
 498 #define FIXP_FRAC (1 << FIXP_N)
 499 #define FIXP_2PI  ((int)(2 * 3.141592653589 * FIXP_FRAC))
 500 #define M_100000PI (3.14159 * 100000)
 501
 502 void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
 503 {
 504         u8 *vbuf = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
 505         unsigned long i;
 506         unsigned long plane_size = vb2_plane_size(&buf->vb.vb2_buf, 0);
 507         s64 s64tmp;
 508         s32 src_phase_step;
 509         s32 mod_phase_step;
 510         s32 fixp_i;
 511         s32 fixp_q;
 512
 513         /* calculate phase step */
 514         #define BEEP_FREQ 1000 /* 1kHz beep */
 515         src_phase_step = DIV_ROUND_CLOSEST(FIXP_2PI * BEEP_FREQ,
 516                                            dev->sdr_adc_freq);
 517
 518         for (i = 0; i < plane_size; i += 2) {
 519                 mod_phase_step = fixp_cos32_rad(dev->sdr_fixp_src_phase,
 520                                                 FIXP_2PI) >> (31 - FIXP_N);
 521
 522                 dev->sdr_fixp_src_phase += src_phase_step;
 523                 s64tmp = (s64) mod_phase_step * dev->sdr_fm_deviation;
 524                 dev->sdr_fixp_mod_phase += div_s64(s64tmp, M_100000PI);
 525
 526                 /*
 527                  * Transfer phase angle to [0, 2xPI] in order to avoid variable
 528                  * overflow and make it suitable for cosine implementation
 529                  * used, which does not support negative angles.
 530                  */
 531                 dev->sdr_fixp_src_phase %= FIXP_2PI;
 532                 dev->sdr_fixp_mod_phase %= FIXP_2PI;
 533
 534                 if (dev->sdr_fixp_mod_phase < 0)
 535                         dev->sdr_fixp_mod_phase += FIXP_2PI;
 536
 537                 fixp_i = fixp_cos32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
 538                 fixp_q = fixp_sin32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
 539
 540                 /* Normalize fraction values represented with 32 bit precision
 541                  * to fixed point representation with FIXP_N bits */
 542                 fixp_i >>= (31 - FIXP_N);
 543                 fixp_q >>= (31 - FIXP_N);
 544
 545                 switch (dev->sdr_pixelformat) {
 546                 case V4L2_SDR_FMT_CU8:
 547                         /* convert 'fixp float' to u8 [0, +255] */
 548                         /* u8 = X * 127.5 + 127.5; X is float [-1.0, +1.0] */
 549                         fixp_i = fixp_i * 1275 + FIXP_FRAC * 1275;
 550                         fixp_q = fixp_q * 1275 + FIXP_FRAC * 1275;
 551                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_i, FIXP_FRAC * 10);
 552                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_q, FIXP_FRAC * 10);
 553                         break;
 554                 case V4L2_SDR_FMT_CS8:
 555                         /* convert 'fixp float' to s8 [-128, +127] */
 556                         /* s8 = X * 127.5 - 0.5; X is float [-1.0, +1.0] */
 557                         fixp_i = fixp_i * 1275 - FIXP_FRAC * 5;
 558                         fixp_q = fixp_q * 1275 - FIXP_FRAC * 5;
 559                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_i, FIXP_FRAC * 10);
 560                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_q, FIXP_FRAC * 10);
 561                         break;
 562                 default:
 563                         break;
 564                 }
 565         }
 566 }