[RFC PATCH 4/7] ASoC: sunxi: sun4i-i2s: Use channel-slots device tree property

[John Watts]

On R329 I2S variants with multiple pins it's useful to read from
multiple devices within a single TDM slot. Allow changing the
assignment of slots through a device tree property.

As an example:

&i2s2 {
        channel-dins = /bits/ 8 <0 0 1 1 2 2>;
        channel-slots = /bits/ 8 <0 1 0 1 0 1>;
};

In addition to configuring the first 6 channels to use different
DIN pins for three separate ADCs, the addition of channel-slots allows
all three ADCs to be sampled within the first two TDM slots.

Signed-off-by: John Watts <contact at jookia.org>
---
 sound/soc/sunxi/sun4i-i2s.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
index 627bf319e1cc..019a4856c90b 100644
--- a/sound/soc/sunxi/sun4i-i2s.c
+++ b/sound/soc/sunxi/sun4i-i2s.c
@@ -269,12 +269,27 @@ static int sun4i_i2s_read_channel_dins(struct device *dev, struct sun4i_i2s *i2s
 
 static int sun4i_i2s_read_channel_slots(struct device *dev, struct sun4i_i2s *i2s)
 {
+	struct device_node *np = dev->of_node;
 	int max_channels = ARRAY_SIZE(i2s->channel_dins);
+	int ret;
 
 	/* Use a 1:1 mapping by default */
 	for (int i = 0; i < max_channels; ++i)
 		i2s->channel_slots[i] = i;
 
+	if (!np)
+		return 0;
+
+	ret = of_property_read_variable_u8_array(np, "channel-slots",
+						 i2s->channel_slots,
+						 1, max_channels);
+
+	if (ret == -EINVAL)
+		return 0;
+
+	if (ret < 0)
+		return ret;
+
 	return 0;
 }
 
-- 
2.41.0