On Thu, May 25, 2017 at 08:46:36PM +0300, Alex A. Mihaylov wrote:

This looks mostly fine, a couple of small things and like I said in
reply to Greg please use subject lines matching the style for the
subsystem - this makes it a lot easier for people to identify relevant
patches.

+	int ret = -ENODEV;
+
+
+	if (reg > 255)
+		return -EINVAL;
+
+	mutex_lock(&sl->master->bus_mutex);
+	if (!w1_reset_select_slave(sl)) {
+		w1_write_8(sl->master, W1_CMD_READ_DATA);
+		w1_write_8(sl->master, reg);
+		*val = w1_read_8(sl->master);
+		ret = 0;
+	}
+	mutex_unlock(&sl->master->bus_mutex);

This is a bit confusing with how -ENODEV is generated - move the
assignment into the if statement so it doesn't look like we're silently
ignoring errors unless you look back to the top of the function.

+static struct regmap_bus regmap_w1_bus_a8_v16 = {
+	.reg_read = w1_reg_a8_v16_read,
+	.reg_write = w1_reg_a8_v16_write,
+};

It'd be clearer to just have all all these structs at the end of the set
of functions rather than scattered about randomly.