1  /*
2   *  PCM Interface - misc routines
3   *  Copyright (c) 1998 by Jaroslav Kysela <perex@perex.cz>
4   *
5   *
6   *   This library is free software; you can redistribute it and/or modify
7   *   it under the terms of the GNU Library General Public License as
8   *   published by the Free Software Foundation; either version 2 of
9   *   the License, or (at your option) any later version.
10   *
11   *   This program is distributed in the hope that it will be useful,
12   *   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14   *   GNU Library General Public License for more details.
15   *
16   *   You should have received a copy of the GNU Library General Public
17   *   License along with this library; if not, write to the Free Software
18   *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
19   *
20   */
21  
22  #include <linux/time.h>
23  #include <linux/export.h>
24  #include <sound/core.h>
25  #include <sound/pcm.h>
26  
27  #include "pcm_local.h"
28  
29  #define SND_PCM_FORMAT_UNKNOWN (-1)
30  
31  /* NOTE: "signed" prefix must be given below since the default char is
32   *       unsigned on some architectures!
33   */
34  struct pcm_format_data {
35  	unsigned char width;	/* bit width */
36  	unsigned char phys;	/* physical bit width */
37  	signed char le;	/* 0 = big-endian, 1 = little-endian, -1 = others */
38  	signed char signd;	/* 0 = unsigned, 1 = signed, -1 = others */
39  	unsigned char silence[8];	/* silence data to fill */
40  };
41  
42  /* we do lots of calculations on snd_pcm_format_t; shut up sparse */
43  #define INT	__force int
44  
valid_format(snd_pcm_format_t format)45  static bool valid_format(snd_pcm_format_t format)
46  {
47  	return (INT)format >= 0 && (INT)format <= (INT)SNDRV_PCM_FORMAT_LAST;
48  }
49  
50  static const struct pcm_format_data pcm_formats[(INT)SNDRV_PCM_FORMAT_LAST+1] = {
51  	[SNDRV_PCM_FORMAT_S8] = {
52  		.width = 8, .phys = 8, .le = -1, .signd = 1,
53  		.silence = {},
54  	},
55  	[SNDRV_PCM_FORMAT_U8] = {
56  		.width = 8, .phys = 8, .le = -1, .signd = 0,
57  		.silence = { 0x80 },
58  	},
59  	[SNDRV_PCM_FORMAT_S16_LE] = {
60  		.width = 16, .phys = 16, .le = 1, .signd = 1,
61  		.silence = {},
62  	},
63  	[SNDRV_PCM_FORMAT_S16_BE] = {
64  		.width = 16, .phys = 16, .le = 0, .signd = 1,
65  		.silence = {},
66  	},
67  	[SNDRV_PCM_FORMAT_U16_LE] = {
68  		.width = 16, .phys = 16, .le = 1, .signd = 0,
69  		.silence = { 0x00, 0x80 },
70  	},
71  	[SNDRV_PCM_FORMAT_U16_BE] = {
72  		.width = 16, .phys = 16, .le = 0, .signd = 0,
73  		.silence = { 0x80, 0x00 },
74  	},
75  	[SNDRV_PCM_FORMAT_S24_LE] = {
76  		.width = 24, .phys = 32, .le = 1, .signd = 1,
77  		.silence = {},
78  	},
79  	[SNDRV_PCM_FORMAT_S24_BE] = {
80  		.width = 24, .phys = 32, .le = 0, .signd = 1,
81  		.silence = {},
82  	},
83  	[SNDRV_PCM_FORMAT_U24_LE] = {
84  		.width = 24, .phys = 32, .le = 1, .signd = 0,
85  		.silence = { 0x00, 0x00, 0x80 },
86  	},
87  	[SNDRV_PCM_FORMAT_U24_BE] = {
88  		.width = 24, .phys = 32, .le = 0, .signd = 0,
89  		.silence = { 0x00, 0x80, 0x00, 0x00 },
90  	},
91  	[SNDRV_PCM_FORMAT_S32_LE] = {
92  		.width = 32, .phys = 32, .le = 1, .signd = 1,
93  		.silence = {},
94  	},
95  	[SNDRV_PCM_FORMAT_S32_BE] = {
96  		.width = 32, .phys = 32, .le = 0, .signd = 1,
97  		.silence = {},
98  	},
99  	[SNDRV_PCM_FORMAT_U32_LE] = {
100  		.width = 32, .phys = 32, .le = 1, .signd = 0,
101  		.silence = { 0x00, 0x00, 0x00, 0x80 },
102  	},
103  	[SNDRV_PCM_FORMAT_U32_BE] = {
104  		.width = 32, .phys = 32, .le = 0, .signd = 0,
105  		.silence = { 0x80, 0x00, 0x00, 0x00 },
106  	},
107  	[SNDRV_PCM_FORMAT_FLOAT_LE] = {
108  		.width = 32, .phys = 32, .le = 1, .signd = -1,
109  		.silence = {},
110  	},
111  	[SNDRV_PCM_FORMAT_FLOAT_BE] = {
112  		.width = 32, .phys = 32, .le = 0, .signd = -1,
113  		.silence = {},
114  	},
115  	[SNDRV_PCM_FORMAT_FLOAT64_LE] = {
116  		.width = 64, .phys = 64, .le = 1, .signd = -1,
117  		.silence = {},
118  	},
119  	[SNDRV_PCM_FORMAT_FLOAT64_BE] = {
120  		.width = 64, .phys = 64, .le = 0, .signd = -1,
121  		.silence = {},
122  	},
123  	[SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE] = {
124  		.width = 32, .phys = 32, .le = 1, .signd = -1,
125  		.silence = {},
126  	},
127  	[SNDRV_PCM_FORMAT_IEC958_SUBFRAME_BE] = {
128  		.width = 32, .phys = 32, .le = 0, .signd = -1,
129  		.silence = {},
130  	},
131  	[SNDRV_PCM_FORMAT_MU_LAW] = {
132  		.width = 8, .phys = 8, .le = -1, .signd = -1,
133  		.silence = { 0x7f },
134  	},
135  	[SNDRV_PCM_FORMAT_A_LAW] = {
136  		.width = 8, .phys = 8, .le = -1, .signd = -1,
137  		.silence = { 0x55 },
138  	},
139  	[SNDRV_PCM_FORMAT_IMA_ADPCM] = {
140  		.width = 4, .phys = 4, .le = -1, .signd = -1,
141  		.silence = {},
142  	},
143  	[SNDRV_PCM_FORMAT_G723_24] = {
144  		.width = 3, .phys = 3, .le = -1, .signd = -1,
145  		.silence = {},
146  	},
147  	[SNDRV_PCM_FORMAT_G723_40] = {
148  		.width = 5, .phys = 5, .le = -1, .signd = -1,
149  		.silence = {},
150  	},
151  	[SNDRV_PCM_FORMAT_DSD_U8] = {
152  		.width = 8, .phys = 8, .le = 1, .signd = 0,
153  		.silence = { 0x69 },
154  	},
155  	[SNDRV_PCM_FORMAT_DSD_U16_LE] = {
156  		.width = 16, .phys = 16, .le = 1, .signd = 0,
157  		.silence = { 0x69, 0x69 },
158  	},
159  	[SNDRV_PCM_FORMAT_DSD_U32_LE] = {
160  		.width = 32, .phys = 32, .le = 1, .signd = 0,
161  		.silence = { 0x69, 0x69, 0x69, 0x69 },
162  	},
163  	[SNDRV_PCM_FORMAT_DSD_U16_BE] = {
164  		.width = 16, .phys = 16, .le = 0, .signd = 0,
165  		.silence = { 0x69, 0x69 },
166  	},
167  	[SNDRV_PCM_FORMAT_DSD_U32_BE] = {
168  		.width = 32, .phys = 32, .le = 0, .signd = 0,
169  		.silence = { 0x69, 0x69, 0x69, 0x69 },
170  	},
171  	/* FIXME: the following two formats are not defined properly yet */
172  	[SNDRV_PCM_FORMAT_MPEG] = {
173  		.le = -1, .signd = -1,
174  	},
175  	[SNDRV_PCM_FORMAT_GSM] = {
176  		.le = -1, .signd = -1,
177  	},
178  	[SNDRV_PCM_FORMAT_S20_LE] = {
179  		.width = 20, .phys = 32, .le = 1, .signd = 1,
180  		.silence = {},
181  	},
182  	[SNDRV_PCM_FORMAT_S20_BE] = {
183  		.width = 20, .phys = 32, .le = 0, .signd = 1,
184  		.silence = {},
185  	},
186  	[SNDRV_PCM_FORMAT_U20_LE] = {
187  		.width = 20, .phys = 32, .le = 1, .signd = 0,
188  		.silence = { 0x00, 0x00, 0x08, 0x00 },
189  	},
190  	[SNDRV_PCM_FORMAT_U20_BE] = {
191  		.width = 20, .phys = 32, .le = 0, .signd = 0,
192  		.silence = { 0x00, 0x08, 0x00, 0x00 },
193  	},
194  	/* FIXME: the following format is not defined properly yet */
195  	[SNDRV_PCM_FORMAT_SPECIAL] = {
196  		.le = -1, .signd = -1,
197  	},
198  	[SNDRV_PCM_FORMAT_S24_3LE] = {
199  		.width = 24, .phys = 24, .le = 1, .signd = 1,
200  		.silence = {},
201  	},
202  	[SNDRV_PCM_FORMAT_S24_3BE] = {
203  		.width = 24, .phys = 24, .le = 0, .signd = 1,
204  		.silence = {},
205  	},
206  	[SNDRV_PCM_FORMAT_U24_3LE] = {
207  		.width = 24, .phys = 24, .le = 1, .signd = 0,
208  		.silence = { 0x00, 0x00, 0x80 },
209  	},
210  	[SNDRV_PCM_FORMAT_U24_3BE] = {
211  		.width = 24, .phys = 24, .le = 0, .signd = 0,
212  		.silence = { 0x80, 0x00, 0x00 },
213  	},
214  	[SNDRV_PCM_FORMAT_S20_3LE] = {
215  		.width = 20, .phys = 24, .le = 1, .signd = 1,
216  		.silence = {},
217  	},
218  	[SNDRV_PCM_FORMAT_S20_3BE] = {
219  		.width = 20, .phys = 24, .le = 0, .signd = 1,
220  		.silence = {},
221  	},
222  	[SNDRV_PCM_FORMAT_U20_3LE] = {
223  		.width = 20, .phys = 24, .le = 1, .signd = 0,
224  		.silence = { 0x00, 0x00, 0x08 },
225  	},
226  	[SNDRV_PCM_FORMAT_U20_3BE] = {
227  		.width = 20, .phys = 24, .le = 0, .signd = 0,
228  		.silence = { 0x08, 0x00, 0x00 },
229  	},
230  	[SNDRV_PCM_FORMAT_S18_3LE] = {
231  		.width = 18, .phys = 24, .le = 1, .signd = 1,
232  		.silence = {},
233  	},
234  	[SNDRV_PCM_FORMAT_S18_3BE] = {
235  		.width = 18, .phys = 24, .le = 0, .signd = 1,
236  		.silence = {},
237  	},
238  	[SNDRV_PCM_FORMAT_U18_3LE] = {
239  		.width = 18, .phys = 24, .le = 1, .signd = 0,
240  		.silence = { 0x00, 0x00, 0x02 },
241  	},
242  	[SNDRV_PCM_FORMAT_U18_3BE] = {
243  		.width = 18, .phys = 24, .le = 0, .signd = 0,
244  		.silence = { 0x02, 0x00, 0x00 },
245  	},
246  	[SNDRV_PCM_FORMAT_G723_24_1B] = {
247  		.width = 3, .phys = 8, .le = -1, .signd = -1,
248  		.silence = {},
249  	},
250  	[SNDRV_PCM_FORMAT_G723_40_1B] = {
251  		.width = 5, .phys = 8, .le = -1, .signd = -1,
252  		.silence = {},
253  	},
254  };
255  
256  
257  /**
258   * snd_pcm_format_signed - Check the PCM format is signed linear
259   * @format: the format to check
260   *
261   * Return: 1 if the given PCM format is signed linear, 0 if unsigned
262   * linear, and a negative error code for non-linear formats.
263   */
snd_pcm_format_signed(snd_pcm_format_t format)264  int snd_pcm_format_signed(snd_pcm_format_t format)
265  {
266  	int val;
267  	if (!valid_format(format))
268  		return -EINVAL;
269  	val = pcm_formats[(INT)format].signd;
270  	if (val < 0)
271  		return -EINVAL;
272  	return val;
273  }
274  EXPORT_SYMBOL(snd_pcm_format_signed);
275  
276  /**
277   * snd_pcm_format_unsigned - Check the PCM format is unsigned linear
278   * @format: the format to check
279   *
280   * Return: 1 if the given PCM format is unsigned linear, 0 if signed
281   * linear, and a negative error code for non-linear formats.
282   */
snd_pcm_format_unsigned(snd_pcm_format_t format)283  int snd_pcm_format_unsigned(snd_pcm_format_t format)
284  {
285  	int val;
286  
287  	val = snd_pcm_format_signed(format);
288  	if (val < 0)
289  		return val;
290  	return !val;
291  }
292  EXPORT_SYMBOL(snd_pcm_format_unsigned);
293  
294  /**
295   * snd_pcm_format_linear - Check the PCM format is linear
296   * @format: the format to check
297   *
298   * Return: 1 if the given PCM format is linear, 0 if not.
299   */
snd_pcm_format_linear(snd_pcm_format_t format)300  int snd_pcm_format_linear(snd_pcm_format_t format)
301  {
302  	return snd_pcm_format_signed(format) >= 0;
303  }
304  EXPORT_SYMBOL(snd_pcm_format_linear);
305  
306  /**
307   * snd_pcm_format_little_endian - Check the PCM format is little-endian
308   * @format: the format to check
309   *
310   * Return: 1 if the given PCM format is little-endian, 0 if
311   * big-endian, or a negative error code if endian not specified.
312   */
snd_pcm_format_little_endian(snd_pcm_format_t format)313  int snd_pcm_format_little_endian(snd_pcm_format_t format)
314  {
315  	int val;
316  	if (!valid_format(format))
317  		return -EINVAL;
318  	val = pcm_formats[(INT)format].le;
319  	if (val < 0)
320  		return -EINVAL;
321  	return val;
322  }
323  EXPORT_SYMBOL(snd_pcm_format_little_endian);
324  
325  /**
326   * snd_pcm_format_big_endian - Check the PCM format is big-endian
327   * @format: the format to check
328   *
329   * Return: 1 if the given PCM format is big-endian, 0 if
330   * little-endian, or a negative error code if endian not specified.
331   */
snd_pcm_format_big_endian(snd_pcm_format_t format)332  int snd_pcm_format_big_endian(snd_pcm_format_t format)
333  {
334  	int val;
335  
336  	val = snd_pcm_format_little_endian(format);
337  	if (val < 0)
338  		return val;
339  	return !val;
340  }
341  EXPORT_SYMBOL(snd_pcm_format_big_endian);
342  
343  /**
344   * snd_pcm_format_width - return the bit-width of the format
345   * @format: the format to check
346   *
347   * Return: The bit-width of the format, or a negative error code
348   * if unknown format.
349   */
snd_pcm_format_width(snd_pcm_format_t format)350  int snd_pcm_format_width(snd_pcm_format_t format)
351  {
352  	int val;
353  	if (!valid_format(format))
354  		return -EINVAL;
355  	val = pcm_formats[(INT)format].width;
356  	if (!val)
357  		return -EINVAL;
358  	return val;
359  }
360  EXPORT_SYMBOL(snd_pcm_format_width);
361  
362  /**
363   * snd_pcm_format_physical_width - return the physical bit-width of the format
364   * @format: the format to check
365   *
366   * Return: The physical bit-width of the format, or a negative error code
367   * if unknown format.
368   */
snd_pcm_format_physical_width(snd_pcm_format_t format)369  int snd_pcm_format_physical_width(snd_pcm_format_t format)
370  {
371  	int val;
372  	if (!valid_format(format))
373  		return -EINVAL;
374  	val = pcm_formats[(INT)format].phys;
375  	if (!val)
376  		return -EINVAL;
377  	return val;
378  }
379  EXPORT_SYMBOL(snd_pcm_format_physical_width);
380  
381  /**
382   * snd_pcm_format_size - return the byte size of samples on the given format
383   * @format: the format to check
384   * @samples: sampling rate
385   *
386   * Return: The byte size of the given samples for the format, or a
387   * negative error code if unknown format.
388   */
snd_pcm_format_size(snd_pcm_format_t format,size_t samples)389  ssize_t snd_pcm_format_size(snd_pcm_format_t format, size_t samples)
390  {
391  	int phys_width = snd_pcm_format_physical_width(format);
392  	if (phys_width < 0)
393  		return -EINVAL;
394  	return samples * phys_width / 8;
395  }
396  EXPORT_SYMBOL(snd_pcm_format_size);
397  
398  /**
399   * snd_pcm_format_silence_64 - return the silent data in 8 bytes array
400   * @format: the format to check
401   *
402   * Return: The format pattern to fill or %NULL if error.
403   */
snd_pcm_format_silence_64(snd_pcm_format_t format)404  const unsigned char *snd_pcm_format_silence_64(snd_pcm_format_t format)
405  {
406  	if (!valid_format(format))
407  		return NULL;
408  	if (! pcm_formats[(INT)format].phys)
409  		return NULL;
410  	return pcm_formats[(INT)format].silence;
411  }
412  EXPORT_SYMBOL(snd_pcm_format_silence_64);
413  
414  /**
415   * snd_pcm_format_set_silence - set the silence data on the buffer
416   * @format: the PCM format
417   * @data: the buffer pointer
418   * @samples: the number of samples to set silence
419   *
420   * Sets the silence data on the buffer for the given samples.
421   *
422   * Return: Zero if successful, or a negative error code on failure.
423   */
snd_pcm_format_set_silence(snd_pcm_format_t format,void * data,unsigned int samples)424  int snd_pcm_format_set_silence(snd_pcm_format_t format, void *data, unsigned int samples)
425  {
426  	int width;
427  	unsigned char *dst;
428  	const unsigned char *pat;
429  
430  	if (!valid_format(format))
431  		return -EINVAL;
432  	if (samples == 0)
433  		return 0;
434  	width = pcm_formats[(INT)format].phys; /* physical width */
435  	pat = pcm_formats[(INT)format].silence;
436  	if (!width || !pat)
437  		return -EINVAL;
438  	/* signed or 1 byte data */
439  	if (pcm_formats[(INT)format].signd == 1 || width <= 8) {
440  		unsigned int bytes = samples * width / 8;
441  		memset(data, *pat, bytes);
442  		return 0;
443  	}
444  	/* non-zero samples, fill using a loop */
445  	width /= 8;
446  	dst = data;
447  #if 0
448  	while (samples--) {
449  		memcpy(dst, pat, width);
450  		dst += width;
451  	}
452  #else
453  	/* a bit optimization for constant width */
454  	switch (width) {
455  	case 2:
456  		while (samples--) {
457  			memcpy(dst, pat, 2);
458  			dst += 2;
459  		}
460  		break;
461  	case 3:
462  		while (samples--) {
463  			memcpy(dst, pat, 3);
464  			dst += 3;
465  		}
466  		break;
467  	case 4:
468  		while (samples--) {
469  			memcpy(dst, pat, 4);
470  			dst += 4;
471  		}
472  		break;
473  	case 8:
474  		while (samples--) {
475  			memcpy(dst, pat, 8);
476  			dst += 8;
477  		}
478  		break;
479  	}
480  #endif
481  	return 0;
482  }
483  EXPORT_SYMBOL(snd_pcm_format_set_silence);
484  
485  /**
486   * snd_pcm_hw_limit_rates - determine rate_min/rate_max fields
487   * @hw: the pcm hw instance
488   *
489   * Determines the rate_min and rate_max fields from the rates bits of
490   * the given hw.
491   *
492   * Return: Zero if successful.
493   */
snd_pcm_hw_limit_rates(struct snd_pcm_hardware * hw)494  int snd_pcm_hw_limit_rates(struct snd_pcm_hardware *hw)
495  {
496  	int i;
497  	unsigned int rmin, rmax;
498  
499  	rmin = UINT_MAX;
500  	rmax = 0;
501  	for (i = 0; i < (int)snd_pcm_known_rates.count; i++) {
502  		if (hw->rates & (1 << i)) {
503  			rmin = min(rmin, snd_pcm_known_rates.list[i]);
504  			rmax = max(rmax, snd_pcm_known_rates.list[i]);
505  		}
506  	}
507  	if (rmin > rmax)
508  		return -EINVAL;
509  	hw->rate_min = rmin;
510  	hw->rate_max = rmax;
511  	return 0;
512  }
513  EXPORT_SYMBOL(snd_pcm_hw_limit_rates);
514  
515  /**
516   * snd_pcm_rate_to_rate_bit - converts sample rate to SNDRV_PCM_RATE_xxx bit
517   * @rate: the sample rate to convert
518   *
519   * Return: The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate, or
520   * SNDRV_PCM_RATE_KNOT for an unknown rate.
521   */
snd_pcm_rate_to_rate_bit(unsigned int rate)522  unsigned int snd_pcm_rate_to_rate_bit(unsigned int rate)
523  {
524  	unsigned int i;
525  
526  	for (i = 0; i < snd_pcm_known_rates.count; i++)
527  		if (snd_pcm_known_rates.list[i] == rate)
528  			return 1u << i;
529  	return SNDRV_PCM_RATE_KNOT;
530  }
531  EXPORT_SYMBOL(snd_pcm_rate_to_rate_bit);
532  
533  /**
534   * snd_pcm_rate_bit_to_rate - converts SNDRV_PCM_RATE_xxx bit to sample rate
535   * @rate_bit: the rate bit to convert
536   *
537   * Return: The sample rate that corresponds to the given SNDRV_PCM_RATE_xxx flag
538   * or 0 for an unknown rate bit.
539   */
snd_pcm_rate_bit_to_rate(unsigned int rate_bit)540  unsigned int snd_pcm_rate_bit_to_rate(unsigned int rate_bit)
541  {
542  	unsigned int i;
543  
544  	for (i = 0; i < snd_pcm_known_rates.count; i++)
545  		if ((1u << i) == rate_bit)
546  			return snd_pcm_known_rates.list[i];
547  	return 0;
548  }
549  EXPORT_SYMBOL(snd_pcm_rate_bit_to_rate);
550  
snd_pcm_rate_mask_sanitize(unsigned int rates)551  static unsigned int snd_pcm_rate_mask_sanitize(unsigned int rates)
552  {
553  	if (rates & SNDRV_PCM_RATE_CONTINUOUS)
554  		return SNDRV_PCM_RATE_CONTINUOUS;
555  	else if (rates & SNDRV_PCM_RATE_KNOT)
556  		return SNDRV_PCM_RATE_KNOT;
557  	return rates;
558  }
559  
560  /**
561   * snd_pcm_rate_mask_intersect - computes the intersection between two rate masks
562   * @rates_a: The first rate mask
563   * @rates_b: The second rate mask
564   *
565   * This function computes the rates that are supported by both rate masks passed
566   * to the function. It will take care of the special handling of
567   * SNDRV_PCM_RATE_CONTINUOUS and SNDRV_PCM_RATE_KNOT.
568   *
569   * Return: A rate mask containing the rates that are supported by both rates_a
570   * and rates_b.
571   */
snd_pcm_rate_mask_intersect(unsigned int rates_a,unsigned int rates_b)572  unsigned int snd_pcm_rate_mask_intersect(unsigned int rates_a,
573  	unsigned int rates_b)
574  {
575  	rates_a = snd_pcm_rate_mask_sanitize(rates_a);
576  	rates_b = snd_pcm_rate_mask_sanitize(rates_b);
577  
578  	if (rates_a & SNDRV_PCM_RATE_CONTINUOUS)
579  		return rates_b;
580  	else if (rates_b & SNDRV_PCM_RATE_CONTINUOUS)
581  		return rates_a;
582  	else if (rates_a & SNDRV_PCM_RATE_KNOT)
583  		return rates_b;
584  	else if (rates_b & SNDRV_PCM_RATE_KNOT)
585  		return rates_a;
586  	return rates_a & rates_b;
587  }
588  EXPORT_SYMBOL_GPL(snd_pcm_rate_mask_intersect);
589  
590  /**
591   * snd_pcm_rate_range_to_bits - converts rate range to SNDRV_PCM_RATE_xxx bit
592   * @rate_min: the minimum sample rate
593   * @rate_max: the maximum sample rate
594   *
595   * This function has an implicit assumption: the rates in the given range have
596   * only the pre-defined rates like 44100 or 16000.
597   *
598   * Return: The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate range,
599   * or SNDRV_PCM_RATE_KNOT for an unknown range.
600   */
snd_pcm_rate_range_to_bits(unsigned int rate_min,unsigned int rate_max)601  unsigned int snd_pcm_rate_range_to_bits(unsigned int rate_min,
602  	unsigned int rate_max)
603  {
604  	unsigned int rates = 0;
605  	int i;
606  
607  	for (i = 0; i < snd_pcm_known_rates.count; i++) {
608  		if (snd_pcm_known_rates.list[i] >= rate_min
609  			&& snd_pcm_known_rates.list[i] <= rate_max)
610  			rates |= 1 << i;
611  	}
612  
613  	if (!rates)
614  		rates = SNDRV_PCM_RATE_KNOT;
615  
616  	return rates;
617  }
618  EXPORT_SYMBOL_GPL(snd_pcm_rate_range_to_bits);
619