From e76bf3c4b4e456fa8f2c729fa1e8c644857529a8 Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Date: Wed, 17 May 2017 08:48:19 +0900
Subject: [PATCH] ALSA: pcm/oss: refer to parameters instead of copying to reduce usage of kernel stack
Git-commit: e76bf3c4b4e456fa8f2c729fa1e8c644857529a8
Patch-mainline: v4.13-rc1
References: bsc#1121278

Some functions in compatibility layer for Open Sound System interface has
local variable to copy some parameters in runtime of PCM substream, while
this can be replaced with reference of pointers to parameter itself. This
brings an advantage to reduce usage of kernel stack.

This commit applies this idea.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/core/oss/pcm_oss.c    | 16 ++++++++--------
 sound/core/oss/pcm_plugin.c |  5 +++--
 sound/core/oss/pcm_plugin.h |  2 +-
 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 2a473513bd54..e306f05ce51d 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -848,7 +848,7 @@ static int snd_pcm_oss_change_params(struct snd_pcm_substream *substream,
 	int direct;
 	snd_pcm_format_t format, sformat;
 	int n;
-	struct snd_mask sformat_mask;
+	const struct snd_mask *sformat_mask;
 	struct snd_mask mask;
 
 	if (trylock) {
@@ -891,18 +891,18 @@ static int snd_pcm_oss_change_params(struct snd_pcm_substream *substream,
 
 	format = snd_pcm_oss_format_from(runtime->oss.format);
 
-	sformat_mask = *hw_param_mask(sparams, SNDRV_PCM_HW_PARAM_FORMAT);
+	sformat_mask = hw_param_mask_c(sparams, SNDRV_PCM_HW_PARAM_FORMAT);
 	if (direct)
 		sformat = format;
 	else
-		sformat = snd_pcm_plug_slave_format(format, &sformat_mask);
+		sformat = snd_pcm_plug_slave_format(format, sformat_mask);
 
 	if ((__force int)sformat < 0 ||
-	    !snd_mask_test(&sformat_mask, (__force int)sformat)) {
+	    !snd_mask_test(sformat_mask, (__force int)sformat)) {
 		for (sformat = (__force snd_pcm_format_t)0;
 		     (__force int)sformat <= (__force int)SNDRV_PCM_FORMAT_LAST;
 		     sformat = (__force snd_pcm_format_t)((__force int)sformat + 1)) {
-			if (snd_mask_test(&sformat_mask, (__force int)sformat) &&
+			if (snd_mask_test(sformat_mask, (__force int)sformat) &&
 			    snd_pcm_oss_format_to(sformat) >= 0)
 				break;
 		}
@@ -1780,7 +1780,7 @@ static int snd_pcm_oss_get_formats(struct snd_pcm_oss_file *pcm_oss_file)
 	int direct;
 	struct snd_pcm_hw_params *params;
 	unsigned int formats = 0;
-	struct snd_mask format_mask;
+	const struct snd_mask *format_mask;
 	int fmt;
 
 	if ((err = snd_pcm_oss_get_active_substream(pcm_oss_file, &substream)) < 0)
@@ -1802,12 +1802,12 @@ static int snd_pcm_oss_get_formats(struct snd_pcm_oss_file *pcm_oss_file)
 		return -ENOMEM;
 	_snd_pcm_hw_params_any(params);
 	err = snd_pcm_hw_refine(substream, params);
-	format_mask = *hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); 
+	format_mask = hw_param_mask_c(params, SNDRV_PCM_HW_PARAM_FORMAT);
 	kfree(params);
 	if (err < 0)
 		return err;
 	for (fmt = 0; fmt < 32; ++fmt) {
-		if (snd_mask_test(&format_mask, fmt)) {
+		if (snd_mask_test(format_mask, fmt)) {
 			int f = snd_pcm_oss_format_to(fmt);
 			if (f >= 0)
 				formats |= f;
diff --git a/sound/core/oss/pcm_plugin.c b/sound/core/oss/pcm_plugin.c
index 727ac44d39f4..cadc93792868 100644
--- a/sound/core/oss/pcm_plugin.c
+++ b/sound/core/oss/pcm_plugin.c
@@ -266,7 +266,8 @@ snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *plug, snd_pc
 	return frames;
 }
 
-static int snd_pcm_plug_formats(struct snd_mask *mask, snd_pcm_format_t format)
+static int snd_pcm_plug_formats(const struct snd_mask *mask,
+				snd_pcm_format_t format)
 {
 	struct snd_mask formats = *mask;
 	u64 linfmts = (SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S8 |
@@ -309,7 +310,7 @@ static snd_pcm_format_t preferred_formats[] = {
 };
 
 snd_pcm_format_t snd_pcm_plug_slave_format(snd_pcm_format_t format,
-					   struct snd_mask *format_mask)
+					   const struct snd_mask *format_mask)
 {
 	int i;
 
diff --git a/sound/core/oss/pcm_plugin.h b/sound/core/oss/pcm_plugin.h
index a5035c2369a6..38e2c14cb893 100644
--- a/sound/core/oss/pcm_plugin.h
+++ b/sound/core/oss/pcm_plugin.h
@@ -126,7 +126,7 @@ int snd_pcm_plug_format_plugins(struct snd_pcm_substream *substream,
 				struct snd_pcm_hw_params *slave_params);
 
 snd_pcm_format_t snd_pcm_plug_slave_format(snd_pcm_format_t format,
-					   struct snd_mask *format_mask);
+					   const struct snd_mask *format_mask);
 
 int snd_pcm_plugin_append(struct snd_pcm_plugin *plugin);
 
-- 
2.20.1