regmap: Add support for writing to regmap registers via debugfs

To enable writing to the regmap debugfs registers file users will
need to modify the source directly and #define REGMAP_ALLOW_WRITE_DEBUGFS.
The reason for this is that it is dangerous to expose this
functionality in general where clients could potentially be PMICs.

[A couple of minor style updates -- broonie]

Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index b3b4b8f..7accb81 100644 (file)
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -103,9 +103,51 @@ out:
        return ret;
 }
 
+#undef REGMAP_ALLOW_WRITE_DEBUGFS
+#ifdef REGMAP_ALLOW_WRITE_DEBUGFS
+/*
+ * This can be dangerous especially when we have clients such as
+ * PMICs, therefore don't provide any real compile time configuration option
+ * for this feature, people who want to use this will need to modify
+ * the source code directly.
+ */
+static ssize_t regmap_map_write_file(struct file *file,
+                                    const char __user *user_buf,
+                                    size_t count, loff_t *ppos)
+{
+       char buf[32];
+       size_t buf_size;
+       char *start = buf;
+       unsigned long reg, value;
+       struct regmap *map = file->private_data;
+
+       buf_size = min(count, (sizeof(buf)-1));
+       if (copy_from_user(buf, user_buf, buf_size))
+               return -EFAULT;
+       buf[buf_size] = 0;
+
+       while (*start == ' ')
+               start++;
+       reg = simple_strtoul(start, &start, 16);
+       while (*start == ' ')
+               start++;
+       if (strict_strtoul(start, 16, &value))
+               return -EINVAL;
+
+       /* Userspace has been fiddling around behind the kernel's back */
+       add_taint(TAINT_USER);
+
+       regmap_write(map, reg, value);
+       return buf_size;
+}
+#else
+#define regmap_map_write_file NULL
+#endif
+
 static const struct file_operations regmap_map_fops = {
        .open = regmap_open_file,
        .read = regmap_map_read_file,
+       .write = regmap_map_write_file,
        .llseek = default_llseek,
 };