ASoC: soc-core: Support debugfs entries larger than PAGE_SIZE bytes

For some codecs with large register maps, it was not possible to dump
all registers via the codec_reg file but only up to PAGE_SIZE bytes.
This patch fixes this problem.

Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 73 insertions, 37 deletions

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 10bc3c23b525..0c789f9150c3 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -87,15 +87,56 @@ static int min_bytes_needed(unsigned long val)
         return c;
 }
 
+/* fill buf which is 'len' bytes with a formatted
+ * string of the form 'reg: value\n' */
+static int format_register_str(struct snd_soc_codec *codec,
+                               unsigned int reg, char *buf, size_t len)
+{
+        int wordsize = codec->driver->reg_word_size * 2;
+        int regsize = min_bytes_needed(codec->driver->reg_cache_size) * 2;
+        int ret;
+        char tmpbuf[len + 1];
+        char regbuf[regsize + 1];
+
+        /* since tmpbuf is allocated on the stack, warn the callers if they
+         * try to abuse this function */
+        WARN_ON(len > 63);
+
+        /* +2 for ': ' and + 1 for '\n' */
+        if (wordsize + regsize + 2 + 1 != len)
+                return -EINVAL;
+
+        ret = snd_soc_read(codec , reg);
+        if (ret < 0) {
+                memset(regbuf, 'X', regsize);
+                regbuf[regsize] = '\0';
+        } else {
+                snprintf(regbuf, regsize + 1, "%.*x", regsize, ret);
+        }
+
+        /* prepare the buffer */
+        snprintf(tmpbuf, len + 1, "%.*x: %s\n", wordsize, reg, regbuf);
+        /* copy it back to the caller without the '\0' */
+        memcpy(buf, tmpbuf, len);
+
+        return 0;
+}
+
 /* codec register dump */
-static ssize_t soc_codec_reg_show(struct snd_soc_codec *codec, char *buf)
+static ssize_t soc_codec_reg_show(struct snd_soc_codec *codec, char *buf,
+                                  size_t count, loff_t pos)
 {
-        int ret, i, step = 1, count = 0;
+        int i, step = 1;
         int wordsize, regsize;
+        int len;
+        size_t total = 0;
+        loff_t p = 0;
 
         wordsize = codec->driver->reg_word_size * 2;
         regsize = min_bytes_needed(codec->driver->reg_cache_size) * 2;
 
+        len = wordsize + regsize + 2 + 1;
+
         if (!codec->driver->reg_cache_size)
                 return 0;
 
@@ -105,51 +146,34 @@ static ssize_t soc_codec_reg_show(struct snd_soc_codec *codec, char *buf)
         for (i = 0; i < codec->driver->reg_cache_size; i += step) {
                 if (codec->readable_register && !codec->readable_register(codec, i))
                         continue;
-
-                count += sprintf(buf + count, "%.*x: ", regsize, i);
-                if (count >= PAGE_SIZE - 1)
-                        break;
-
                 if (codec->driver->display_register) {
                         count += codec->driver->display_register(codec, buf + count,
                                                          PAGE_SIZE - count, i);
                 } else {
-                        /* If the read fails it's almost certainly due to
-                         * the register being volatile and the device being
-                         * powered off.
-                         */
-                        ret = snd_soc_read(codec, i);
-                        if (ret >= 0)
-                                count += snprintf(buf + count,
-                                                  PAGE_SIZE - count,
-                                                  "%.*x", wordsize, ret);
-                        else
-                                count += snprintf(buf + count,
-                                                  PAGE_SIZE - count,
-                                                  "<no data: %d>", ret);
+                        /* only support larger than PAGE_SIZE bytes debugfs
+                         * entries for the default case */
+                        if (p >= pos) {
+                                if (total + len >= count - 1)
+                                        break;
+                                format_register_str(codec, i, buf + total, len);
+                                total += len;
+                        }
+                        p += len;
                 }
-
-                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;
+        total = min(total, count - 1);
 
-        return count;
+        return total;
 }
+
 static ssize_t codec_reg_show(struct device *dev,
         struct device_attribute *attr, char *buf)
 {
         struct snd_soc_pcm_runtime *rtd =
                         container_of(dev, struct snd_soc_pcm_runtime, dev);
 
-        return soc_codec_reg_show(rtd->codec, buf);
+        return soc_codec_reg_show(rtd->codec, buf, PAGE_SIZE, 0);
 }
 
 static DEVICE_ATTR(codec_reg, 0444, codec_reg_show, NULL);
@@ -188,16 +212,28 @@ static int codec_reg_open_file(struct inode *inode, struct file *file)
 }
 
 static ssize_t codec_reg_read_file(struct file *file, char __user *user_buf,
-                               size_t count, loff_t *ppos)
+                                   size_t count, loff_t *ppos)
 {
         ssize_t ret;
         struct snd_soc_codec *codec = file->private_data;
-        char *buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+        char *buf;
+
+        if (*ppos < 0 || !count)
+                return -EINVAL;
+
+        buf = kmalloc(count, GFP_KERNEL);
         if (!buf)
                 return -ENOMEM;
-        ret = soc_codec_reg_show(codec, buf);
-        if (ret >= 0)
-                ret = simple_read_from_buffer(user_buf, count, ppos, buf, ret);
+
+        ret = soc_codec_reg_show(codec, buf, count, *ppos);
+        if (ret >= 0) {
+                if (copy_to_user(user_buf, buf, ret)) {
+                        kfree(buf);
+                        return -EFAULT;
+                }
+                *ppos += ret;
+        }
+
         kfree(buf);
         return ret;
 }