[PATCH 04/14] ASoC: Allow codecs to override register display

[Mark Brown <broonie@opensource.wolfsonmicro.com>]

Some codecs have unusual features in their register maps such as very
large registers representing arrays of coefficients. Support these
codecs in the register cache sysfs file by allowing them to provide a
function register_display() overriding the default output for register
contents.

Also ensure that we don't overflow PAGE_SIZE while writing out the
register dump.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
---
 include/sound/soc.h  |    2 ++
 sound/soc/soc-core.c |   26 +++++++++++++++++++++++---
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 1890d87..2ce530e 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -410,6 +410,8 @@ struct snd_soc_codec {
 	void *control_data; /* codec control (i2c/3wire) data */
 	unsigned int (*read)(struct snd_soc_codec *, unsigned int);
 	int (*write)(struct snd_soc_codec *, unsigned int, unsigned int);
+	int (*display_register)(struct snd_soc_codec *, char *,
+				size_t, unsigned int);
 	hw_write_t hw_write;
 	hw_read_t hw_read;
 	void *reg_cache;
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 83f1190..5d3bf73 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -970,9 +970,29 @@ static ssize_t codec_reg_show(struct device *dev,
 		step = codec->reg_cache_step;
 
 	count += sprintf(buf, "%s registers\n", codec->name);
-	for (i = 0; i < codec->reg_cache_size; i += step)
-		count += sprintf(buf + count, "%2x: %4x\n", i,
-			codec->read(codec, i));
+	for (i = 0; i < codec->reg_cache_size; i += step) {
+		count += sprintf(buf + count, "%2x: ", i);
+		if (count >= PAGE_SIZE - 1)
+			break;
+
+		if (codec->display_register)
+			count += codec->display_register(codec, buf + count,
+							 PAGE_SIZE - count, i);
+		else
+			count += snprintf(buf + count, PAGE_SIZE - count,
+					  "%4x", codec->read(codec, i));
+
+		if (count >= PAGE_SIZE - 1)
+			break;
+
+		count += snprintf(buf + count, PAGE_SIZE - count, "\n");
+		if (count >= PAGE_SIZE - 1)
+			break;
+	}
+
+	/* Truncate count; min() would cause a warning */
+	if (count >= PAGE_SIZE)
+		count = PAGE_SIZE - 1;
 
 	return count;
 }
-- 
1.5.6.3