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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * vivid-sdr-cap.c - software defined radio support functions.
   4  *
   5  * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
   6  */
   7
   8 #include <linux/errno.h>
   9 #include <linux/kernel.h>
  10 #include <linux/delay.h>
  11 #include <linux/kthread.h>
  12 #include <linux/freezer.h>
  13 #include <linux/math64.h>
  14 #include <linux/videodev2.h>
  15 #include <linux/v4l2-dv-timings.h>
  16 #include <media/v4l2-common.h>
  17 #include <media/v4l2-event.h>
  18 #include <media/v4l2-dv-timings.h>
  19 #include <linux/fixp-arith.h>
  20
  21 #include "vivid-core.h"
  22 #include "vivid-ctrls.h"
  23 #include "vivid-sdr-cap.h"
  24
  25 /* stream formats */
  26 struct vivid_format {
  27         u32     pixelformat;
  28         u32     buffersize;
  29 };
  30
  31 /* format descriptions for capture and preview */
  32 static const struct vivid_format formats[] = {
  33         {
  34                 .pixelformat    = V4L2_SDR_FMT_CU8,
  35                 .buffersize     = SDR_CAP_SAMPLES_PER_BUF * 2,
  36         }, {
  37                 .pixelformat    = V4L2_SDR_FMT_CS8,
  38                 .buffersize     = SDR_CAP_SAMPLES_PER_BUF * 2,
  39         },
  40 };
  41
  42 static const struct v4l2_frequency_band bands_adc[] = {
  43         {
  44                 .tuner = 0,
  45                 .type = V4L2_TUNER_ADC,
  46                 .index = 0,
  47                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  48                 .rangelow   =  300000,
  49                 .rangehigh  =  300000,
  50         },
  51         {
  52                 .tuner = 0,
  53                 .type = V4L2_TUNER_ADC,
  54                 .index = 1,
  55                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  56                 .rangelow   =  900001,
  57                 .rangehigh  = 2800000,
  58         },
  59         {
  60                 .tuner = 0,
  61                 .type = V4L2_TUNER_ADC,
  62                 .index = 2,
  63                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  64                 .rangelow   = 3200000,
  65                 .rangehigh  = 3200000,
  66         },
  67 };
  68
  69 /* ADC band midpoints */
  70 #define BAND_ADC_0 ((bands_adc[0].rangehigh + bands_adc[1].rangelow) / 2)
  71 #define BAND_ADC_1 ((bands_adc[1].rangehigh + bands_adc[2].rangelow) / 2)
  72
  73 static const struct v4l2_frequency_band bands_fm[] = {
  74         {
  75                 .tuner = 1,
  76                 .type = V4L2_TUNER_RF,
  77                 .index = 0,
  78                 .capability = V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS,
  79                 .rangelow   =    50000000,
  80                 .rangehigh  =  2000000000,
  81         },
  82 };
  83
  84 static void vivid_thread_sdr_cap_tick(struct vivid_dev *dev)
  85 {
  86         struct vivid_buffer *sdr_cap_buf = NULL;
  87
  88         dprintk(dev, 1, "SDR Capture Thread Tick\n");
  89
  90         /* Drop a certain percentage of buffers. */
  91         if (dev->perc_dropped_buffers &&
  92             prandom_u32_max(100) < dev->perc_dropped_buffers)
  93                 return;
  94
  95         spin_lock(&dev->slock);
  96         if (!list_empty(&dev->sdr_cap_active)) {
  97                 sdr_cap_buf = list_entry(dev->sdr_cap_active.next,
  98                                          struct vivid_buffer, list);
  99                 list_del(&sdr_cap_buf->list);
 100         }
 101         spin_unlock(&dev->slock);
 102
 103         if (sdr_cap_buf) {
 104                 sdr_cap_buf->vb.sequence = dev->sdr_cap_seq_count;
 105                 v4l2_ctrl_request_setup(sdr_cap_buf->vb.vb2_buf.req_obj.req,
 106                                         &dev->ctrl_hdl_sdr_cap);
 107                 v4l2_ctrl_request_complete(sdr_cap_buf->vb.vb2_buf.req_obj.req,
 108                                            &dev->ctrl_hdl_sdr_cap);
 109                 vivid_sdr_cap_process(dev, sdr_cap_buf);
 110                 sdr_cap_buf->vb.vb2_buf.timestamp =
 111                         ktime_get_ns() + dev->time_wrap_offset;
 112                 vb2_buffer_done(&sdr_cap_buf->vb.vb2_buf, dev->dqbuf_error ?
 113                                 VB2_BUF_STATE_ERROR : VB2_BUF_STATE_DONE);
 114                 dev->dqbuf_error = false;
 115         }
 116 }
 117
 118 static int vivid_thread_sdr_cap(void *data)
 119 {
 120         struct vivid_dev *dev = data;
 121         u64 samples_since_start;
 122         u64 buffers_since_start;
 123         u64 next_jiffies_since_start;
 124         unsigned long jiffies_since_start;
 125         unsigned long cur_jiffies;
 126         unsigned wait_jiffies;
 127
 128         dprintk(dev, 1, "SDR Capture Thread Start\n");
 129
 130         set_freezable();
 131
 132         /* Resets frame counters */
 133         dev->sdr_cap_seq_offset = 0;
 134         if (dev->seq_wrap)
 135                 dev->sdr_cap_seq_offset = 0xffffff80U;
 136         dev->jiffies_sdr_cap = jiffies;
 137         dev->sdr_cap_seq_resync = false;
 138
 139         for (;;) {
 140                 try_to_freeze();
 141                 if (kthread_should_stop())
 142                         break;
 143
 144                 mutex_lock(&dev->mutex);
 145                 cur_jiffies = jiffies;
 146                 if (dev->sdr_cap_seq_resync) {
 147                         dev->jiffies_sdr_cap = cur_jiffies;
 148                         dev->sdr_cap_seq_offset = dev->sdr_cap_seq_count + 1;
 149                         dev->sdr_cap_seq_count = 0;
 150                         dev->sdr_cap_seq_resync = false;
 151                 }
 152                 /* Calculate the number of jiffies since we started streaming */
 153                 jiffies_since_start = cur_jiffies - dev->jiffies_sdr_cap;
 154                 /* Get the number of buffers streamed since the start */
 155                 buffers_since_start =
 156                         (u64)jiffies_since_start * dev->sdr_adc_freq +
 157                                       (HZ * SDR_CAP_SAMPLES_PER_BUF) / 2;
 158                 do_div(buffers_since_start, HZ * SDR_CAP_SAMPLES_PER_BUF);
 159
 160                 /*
 161                  * After more than 0xf0000000 (rounded down to a multiple of
 162                  * 'jiffies-per-day' to ease jiffies_to_msecs calculation)
 163                  * jiffies have passed since we started streaming reset the
 164                  * counters and keep track of the sequence offset.
 165                  */
 166                 if (jiffies_since_start > JIFFIES_RESYNC) {
 167                         dev->jiffies_sdr_cap = cur_jiffies;
 168                         dev->sdr_cap_seq_offset = buffers_since_start;
 169                         buffers_since_start = 0;
 170                 }
 171                 dev->sdr_cap_seq_count =
 172                         buffers_since_start + dev->sdr_cap_seq_offset;
 173
 174                 vivid_thread_sdr_cap_tick(dev);
 175                 mutex_unlock(&dev->mutex);
 176
 177                 /*
 178                  * Calculate the number of samples streamed since we started,
 179                  * not including the current buffer.
 180                  */
 181                 samples_since_start = buffers_since_start * SDR_CAP_SAMPLES_PER_BUF;
 182
 183                 /* And the number of jiffies since we started */
 184                 jiffies_since_start = jiffies - dev->jiffies_sdr_cap;
 185
 186                 /* Increase by the number of samples in one buffer */
 187                 samples_since_start += SDR_CAP_SAMPLES_PER_BUF;
 188                 /*
 189                  * Calculate when that next buffer is supposed to start
 190                  * in jiffies since we started streaming.
 191                  */
 192                 next_jiffies_since_start = samples_since_start * HZ +
 193                                            dev->sdr_adc_freq / 2;
 194                 do_div(next_jiffies_since_start, dev->sdr_adc_freq);
 195                 /* If it is in the past, then just schedule asap */
 196                 if (next_jiffies_since_start < jiffies_since_start)
 197                         next_jiffies_since_start = jiffies_since_start;
 198
 199                 wait_jiffies = next_jiffies_since_start - jiffies_since_start;
 200                 schedule_timeout_interruptible(wait_jiffies ? wait_jiffies : 1);
 201         }
 202         dprintk(dev, 1, "SDR Capture Thread End\n");
 203         return 0;
 204 }
 205
 206 static int sdr_cap_queue_setup(struct vb2_queue *vq,
 207                        unsigned *nbuffers, unsigned *nplanes,
 208                        unsigned sizes[], struct device *alloc_devs[])
 209 {
 210         /* 2 = max 16-bit sample returned */
 211         sizes[0] = SDR_CAP_SAMPLES_PER_BUF * 2;
 212         *nplanes = 1;
 213         return 0;
 214 }
 215
 216 static int sdr_cap_buf_prepare(struct vb2_buffer *vb)
 217 {
 218         struct vivid_dev *dev = vb2_get_drv_priv(vb->vb2_queue);
 219         unsigned size = SDR_CAP_SAMPLES_PER_BUF * 2;
 220
 221         dprintk(dev, 1, "%s\n", __func__);
 222
 223         if (dev->buf_prepare_error) {
 224                 /*
 225                  * Error injection: test what happens if buf_prepare() returns
 226                  * an error.
 227                  */
 228                 dev->buf_prepare_error = false;
 229                 return -EINVAL;
 230         }
 231         if (vb2_plane_size(vb, 0) < size) {
 232                 dprintk(dev, 1, "%s data will not fit into plane (%lu < %u)\n",
 233                                 __func__, vb2_plane_size(vb, 0), size);
 234                 return -EINVAL;
 235         }
 236         vb2_set_plane_payload(vb, 0, size);
 237
 238         return 0;
 239 }
 240
 241 static void sdr_cap_buf_queue(struct vb2_buffer *vb)
 242 {
 243         struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
 244         struct vivid_dev *dev = vb2_get_drv_priv(vb->vb2_queue);
 245         struct vivid_buffer *buf = container_of(vbuf, struct vivid_buffer, vb);
 246
 247         dprintk(dev, 1, "%s\n", __func__);
 248
 249         spin_lock(&dev->slock);
 250         list_add_tail(&buf->list, &dev->sdr_cap_active);
 251         spin_unlock(&dev->slock);
 252 }
 253
 254 static int sdr_cap_start_streaming(struct vb2_queue *vq, unsigned count)
 255 {
 256         struct vivid_dev *dev = vb2_get_drv_priv(vq);
 257         int err = 0;
 258
 259         dprintk(dev, 1, "%s\n", __func__);
 260         dev->sdr_cap_seq_count = 0;
 261         if (dev->start_streaming_error) {
 262                 dev->start_streaming_error = false;
 263                 err = -EINVAL;
 264         } else if (dev->kthread_sdr_cap == NULL) {
 265                 dev->kthread_sdr_cap = kthread_run(vivid_thread_sdr_cap, dev,
 266                                 "%s-sdr-cap", dev->v4l2_dev.name);
 267
 268                 if (IS_ERR(dev->kthread_sdr_cap)) {
 269                         v4l2_err(&dev->v4l2_dev, "kernel_thread() failed\n");
 270                         err = PTR_ERR(dev->kthread_sdr_cap);
 271                         dev->kthread_sdr_cap = NULL;
 272                 }
 273         }
 274         if (err) {
 275                 struct vivid_buffer *buf, *tmp;
 276
 277                 list_for_each_entry_safe(buf, tmp, &dev->sdr_cap_active, list) {
 278                         list_del(&buf->list);
 279                         v4l2_ctrl_request_complete(buf->vb.vb2_buf.req_obj.req,
 280                                                    &dev->ctrl_hdl_sdr_cap);
 281                         vb2_buffer_done(&buf->vb.vb2_buf,
 282                                         VB2_BUF_STATE_QUEUED);
 283                 }
 284         }
 285         return err;
 286 }
 287
 288 /* abort streaming and wait for last buffer */
 289 static void sdr_cap_stop_streaming(struct vb2_queue *vq)
 290 {
 291         struct vivid_dev *dev = vb2_get_drv_priv(vq);
 292
 293         if (dev->kthread_sdr_cap == NULL)
 294                 return;
 295
 296         while (!list_empty(&dev->sdr_cap_active)) {
 297                 struct vivid_buffer *buf;
 298
 299                 buf = list_entry(dev->sdr_cap_active.next,
 300                                 struct vivid_buffer, list);
 301                 list_del(&buf->list);
 302                 v4l2_ctrl_request_complete(buf->vb.vb2_buf.req_obj.req,
 303                                            &dev->ctrl_hdl_sdr_cap);
 304                 vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
 305         }
 306
 307         /* shutdown control thread */
 308         mutex_unlock(&dev->mutex);
 309         kthread_stop(dev->kthread_sdr_cap);
 310         dev->kthread_sdr_cap = NULL;
 311         mutex_lock(&dev->mutex);
 312 }
 313
 314 static void sdr_cap_buf_request_complete(struct vb2_buffer *vb)
 315 {
 316         struct vivid_dev *dev = vb2_get_drv_priv(vb->vb2_queue);
 317
 318         v4l2_ctrl_request_complete(vb->req_obj.req, &dev->ctrl_hdl_sdr_cap);
 319 }
 320
 321 const struct vb2_ops vivid_sdr_cap_qops = {
 322         .queue_setup            = sdr_cap_queue_setup,
 323         .buf_prepare            = sdr_cap_buf_prepare,
 324         .buf_queue              = sdr_cap_buf_queue,
 325         .start_streaming        = sdr_cap_start_streaming,
 326         .stop_streaming         = sdr_cap_stop_streaming,
 327         .buf_request_complete   = sdr_cap_buf_request_complete,
 328         .wait_prepare           = vb2_ops_wait_prepare,
 329         .wait_finish            = vb2_ops_wait_finish,
 330 };
 331
 332 int vivid_sdr_enum_freq_bands(struct file *file, void *fh,
 333                 struct v4l2_frequency_band *band)
 334 {
 335         switch (band->tuner) {
 336         case 0:
 337                 if (band->index >= ARRAY_SIZE(bands_adc))
 338                         return -EINVAL;
 339                 *band = bands_adc[band->index];
 340                 return 0;
 341         case 1:
 342                 if (band->index >= ARRAY_SIZE(bands_fm))
 343                         return -EINVAL;
 344                 *band = bands_fm[band->index];
 345                 return 0;
 346         default:
 347                 return -EINVAL;
 348         }
 349 }
 350
 351 int vivid_sdr_g_frequency(struct file *file, void *fh,
 352                 struct v4l2_frequency *vf)
 353 {
 354         struct vivid_dev *dev = video_drvdata(file);
 355
 356         switch (vf->tuner) {
 357         case 0:
 358                 vf->frequency = dev->sdr_adc_freq;
 359                 vf->type = V4L2_TUNER_ADC;
 360                 return 0;
 361         case 1:
 362                 vf->frequency = dev->sdr_fm_freq;
 363                 vf->type = V4L2_TUNER_RF;
 364                 return 0;
 365         default:
 366                 return -EINVAL;
 367         }
 368 }
 369
 370 int vivid_sdr_s_frequency(struct file *file, void *fh,
 371                 const struct v4l2_frequency *vf)
 372 {
 373         struct vivid_dev *dev = video_drvdata(file);
 374         unsigned freq = vf->frequency;
 375         unsigned band;
 376
 377         switch (vf->tuner) {
 378         case 0:
 379                 if (vf->type != V4L2_TUNER_ADC)
 380                         return -EINVAL;
 381                 if (freq < BAND_ADC_0)
 382                         band = 0;
 383                 else if (freq < BAND_ADC_1)
 384                         band = 1;
 385                 else
 386                         band = 2;
 387
 388                 freq = clamp_t(unsigned, freq,
 389                                 bands_adc[band].rangelow,
 390                                 bands_adc[band].rangehigh);
 391
 392                 if (vb2_is_streaming(&dev->vb_sdr_cap_q) &&
 393                     freq != dev->sdr_adc_freq) {
 394                         /* resync the thread's timings */
 395                         dev->sdr_cap_seq_resync = true;
 396                 }
 397                 dev->sdr_adc_freq = freq;
 398                 return 0;
 399         case 1:
 400                 if (vf->type != V4L2_TUNER_RF)
 401                         return -EINVAL;
 402                 dev->sdr_fm_freq = clamp_t(unsigned, freq,
 403                                 bands_fm[0].rangelow,
 404                                 bands_fm[0].rangehigh);
 405                 return 0;
 406         default:
 407                 return -EINVAL;
 408         }
 409 }
 410
 411 int vivid_sdr_g_tuner(struct file *file, void *fh, struct v4l2_tuner *vt)
 412 {
 413         switch (vt->index) {
 414         case 0:
 415                 strscpy(vt->name, "ADC", sizeof(vt->name));
 416                 vt->type = V4L2_TUNER_ADC;
 417                 vt->capability =
 418                         V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS;
 419                 vt->rangelow = bands_adc[0].rangelow;
 420                 vt->rangehigh = bands_adc[2].rangehigh;
 421                 return 0;
 422         case 1:
 423                 strscpy(vt->name, "RF", sizeof(vt->name));
 424                 vt->type = V4L2_TUNER_RF;
 425                 vt->capability =
 426                         V4L2_TUNER_CAP_1HZ | V4L2_TUNER_CAP_FREQ_BANDS;
 427                 vt->rangelow = bands_fm[0].rangelow;
 428                 vt->rangehigh = bands_fm[0].rangehigh;
 429                 return 0;
 430         default:
 431                 return -EINVAL;
 432         }
 433 }
 434
 435 int vivid_sdr_s_tuner(struct file *file, void *fh, const struct v4l2_tuner *vt)
 436 {
 437         if (vt->index > 1)
 438                 return -EINVAL;
 439         return 0;
 440 }
 441
 442 int vidioc_enum_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_fmtdesc *f)
 443 {
 444         if (f->index >= ARRAY_SIZE(formats))
 445                 return -EINVAL;
 446         f->pixelformat = formats[f->index].pixelformat;
 447         return 0;
 448 }
 449
 450 int vidioc_g_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
 451 {
 452         struct vivid_dev *dev = video_drvdata(file);
 453
 454         f->fmt.sdr.pixelformat = dev->sdr_pixelformat;
 455         f->fmt.sdr.buffersize = dev->sdr_buffersize;
 456         memset(f->fmt.sdr.reserved, 0, sizeof(f->fmt.sdr.reserved));
 457         return 0;
 458 }
 459
 460 int vidioc_s_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
 461 {
 462         struct vivid_dev *dev = video_drvdata(file);
 463         struct vb2_queue *q = &dev->vb_sdr_cap_q;
 464         int i;
 465
 466         if (vb2_is_busy(q))
 467                 return -EBUSY;
 468
 469         memset(f->fmt.sdr.reserved, 0, sizeof(f->fmt.sdr.reserved));
 470         for (i = 0; i < ARRAY_SIZE(formats); i++) {
 471                 if (formats[i].pixelformat == f->fmt.sdr.pixelformat) {
 472                         dev->sdr_pixelformat = formats[i].pixelformat;
 473                         dev->sdr_buffersize = formats[i].buffersize;
 474                         f->fmt.sdr.buffersize = formats[i].buffersize;
 475                         return 0;
 476                 }
 477         }
 478         dev->sdr_pixelformat = formats[0].pixelformat;
 479         dev->sdr_buffersize = formats[0].buffersize;
 480         f->fmt.sdr.pixelformat = formats[0].pixelformat;
 481         f->fmt.sdr.buffersize = formats[0].buffersize;
 482         return 0;
 483 }
 484
 485 int vidioc_try_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
 486 {
 487         int i;
 488
 489         memset(f->fmt.sdr.reserved, 0, sizeof(f->fmt.sdr.reserved));
 490         for (i = 0; i < ARRAY_SIZE(formats); i++) {
 491                 if (formats[i].pixelformat == f->fmt.sdr.pixelformat) {
 492                         f->fmt.sdr.buffersize = formats[i].buffersize;
 493                         return 0;
 494                 }
 495         }
 496         f->fmt.sdr.pixelformat = formats[0].pixelformat;
 497         f->fmt.sdr.buffersize = formats[0].buffersize;
 498         return 0;
 499 }
 500
 501 #define FIXP_N    (15)
 502 #define FIXP_FRAC (1 << FIXP_N)
 503 #define FIXP_2PI  ((int)(2 * 3.141592653589 * FIXP_FRAC))
 504 #define M_100000PI (3.14159 * 100000)
 505
 506 void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
 507 {
 508         u8 *vbuf = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
 509         unsigned long i;
 510         unsigned long plane_size = vb2_plane_size(&buf->vb.vb2_buf, 0);
 511         s64 s64tmp;
 512         s32 src_phase_step;
 513         s32 mod_phase_step;
 514         s32 fixp_i;
 515         s32 fixp_q;
 516
 517         /* calculate phase step */
 518         #define BEEP_FREQ 1000 /* 1kHz beep */
 519         src_phase_step = DIV_ROUND_CLOSEST(FIXP_2PI * BEEP_FREQ,
 520                                            dev->sdr_adc_freq);
 521
 522         for (i = 0; i < plane_size; i += 2) {
 523                 mod_phase_step = fixp_cos32_rad(dev->sdr_fixp_src_phase,
 524                                                 FIXP_2PI) >> (31 - FIXP_N);
 525
 526                 dev->sdr_fixp_src_phase += src_phase_step;
 527                 s64tmp = (s64) mod_phase_step * dev->sdr_fm_deviation;
 528                 dev->sdr_fixp_mod_phase += div_s64(s64tmp, M_100000PI);
 529
 530                 /*
 531                  * Transfer phase angle to [0, 2xPI] in order to avoid variable
 532                  * overflow and make it suitable for cosine implementation
 533                  * used, which does not support negative angles.
 534                  */
 535                 dev->sdr_fixp_src_phase %= FIXP_2PI;
 536                 dev->sdr_fixp_mod_phase %= FIXP_2PI;
 537
 538                 if (dev->sdr_fixp_mod_phase < 0)
 539                         dev->sdr_fixp_mod_phase += FIXP_2PI;
 540
 541                 fixp_i = fixp_cos32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
 542                 fixp_q = fixp_sin32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
 543
 544                 /* Normalize fraction values represented with 32 bit precision
 545                  * to fixed point representation with FIXP_N bits */
 546                 fixp_i >>= (31 - FIXP_N);
 547                 fixp_q >>= (31 - FIXP_N);
 548
 549                 switch (dev->sdr_pixelformat) {
 550                 case V4L2_SDR_FMT_CU8:
 551                         /* convert 'fixp float' to u8 [0, +255] */
 552                         /* u8 = X * 127.5 + 127.5; X is float [-1.0, +1.0] */
 553                         fixp_i = fixp_i * 1275 + FIXP_FRAC * 1275;
 554                         fixp_q = fixp_q * 1275 + FIXP_FRAC * 1275;
 555                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_i, FIXP_FRAC * 10);
 556                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_q, FIXP_FRAC * 10);
 557                         break;
 558                 case V4L2_SDR_FMT_CS8:
 559                         /* convert 'fixp float' to s8 [-128, +127] */
 560                         /* s8 = X * 127.5 - 0.5; X is float [-1.0, +1.0] */
 561                         fixp_i = fixp_i * 1275 - FIXP_FRAC * 5;
 562                         fixp_q = fixp_q * 1275 - FIXP_FRAC * 5;
 563                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_i, FIXP_FRAC * 10);
 564                         *vbuf++ = DIV_ROUND_CLOSEST(fixp_q, FIXP_FRAC * 10);
 565                         break;
 566                 default:
 567                         break;
 568                 }
 569         }
 570 }