ALSA: pcm: use helper function to refer parameter as read-only

ALSA pcm core has hw_param_interval_c() to pick up parameter with const
qualifier for safe programming.

This commit applies it to the cases.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/oss/pcm_oss.c

@@ -799,7 +799,7 @@ static int snd_pcm_oss_period_size(struct snd_pcm_substream *substream,
 static int choose_rate(struct snd_pcm_substream *substream,
 		       struct snd_pcm_hw_params *params, unsigned int best_rate)
 {
-	struct snd_interval *it;
+	const struct snd_interval *it;
 	struct snd_pcm_hw_params *save;
 	unsigned int rate, prev;
 
@@ -807,7 +807,7 @@ static int choose_rate(struct snd_pcm_substream *substream,
 	if (save == NULL)
 		return -ENOMEM;
 	*save = *params;
-	it = hw_param_interval(save, SNDRV_PCM_HW_PARAM_RATE);
+	it = hw_param_interval_c(save, SNDRV_PCM_HW_PARAM_RATE);
 
 	/* try multiples of the best rate */
 	rate = best_rate;

sound/core/pcm_drm_eld.c

@@ -29,13 +29,13 @@ static int eld_limit_rates(struct snd_pcm_hw_params *params,
 			   struct snd_pcm_hw_rule *rule)
 {
 	struct snd_interval *r = hw_param_interval(params, rule->var);
-	struct snd_interval *c;
+	const struct snd_interval *c;
 	unsigned int rate_mask = 7, i;
 	const u8 *sad, *eld = rule->private;
 
 	sad = drm_eld_sad(eld);
 	if (sad) {
-		c = hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
+		c = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_CHANNELS);
 
 		for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
 			unsigned max_channels = sad_max_channels(sad);
@@ -57,7 +57,7 @@ static int eld_limit_channels(struct snd_pcm_hw_params *params,
 			      struct snd_pcm_hw_rule *rule)
 {
 	struct snd_interval *c = hw_param_interval(params, rule->var);
-	struct snd_interval *r;
+	const struct snd_interval *r;
 	struct snd_interval t = { .min = 1, .max = 2, .integer = 1, };
 	unsigned int i;
 	const u8 *sad, *eld = rule->private;
@@ -67,7 +67,7 @@ static int eld_limit_channels(struct snd_pcm_hw_params *params,
 		unsigned int rate_mask = 0;
 
 		/* Convert the rate interval to a mask */
-		r = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
+		r = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);
 		for (i = 0; i < ARRAY_SIZE(eld_rates); i++)
 			if (r->min <= eld_rates[i] && r->max >= eld_rates[i])
 				rate_mask |= BIT(i);

sound/core/pcm_lib.c

@@ -1415,7 +1415,8 @@ static int snd_pcm_hw_rule_msbits(struct snd_pcm_hw_params *params,
 	unsigned int l = (unsigned long) rule->private;
 	int width = l & 0xffff;
 	unsigned int msbits = l >> 16;
-	struct snd_interval *i = hw_param_interval(params, SNDRV_PCM_HW_PARAM_SAMPLE_BITS);
+	const struct snd_interval *i =
+		hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_SAMPLE_BITS);
 
 	if (!snd_interval_single(i))
 		return 0;

sound/core/pcm_native.c

@@ -1940,7 +1940,8 @@ static int snd_pcm_hw_rule_format(struct snd_pcm_hw_params *params,
 				  struct snd_pcm_hw_rule *rule)
 {
 	unsigned int k;
-	struct snd_interval *i = hw_param_interval(params, rule->deps[0]);
+	const struct snd_interval *i =
+				hw_param_interval_c(params, rule->deps[0]);
 	struct snd_mask m;
 	struct snd_mask *mask = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
 	snd_mask_any(&m);