On Sun, Jul 01, 2018 at 01:08:04PM +0200, Andreas F?rber wrote:

+static void sx1301_radio_spi_set_cs(struct spi_device *spi, bool enable)
+{
+	int ret;
+
+	dev_dbg(&spi->dev, "setting SPI CS to %s\n", enable ? "1" : "0");
+
+	if (enable)
+		return;
+
+	ret = sx1301_radio_set_cs(spi->controller, enable);
+	if (ret)
+		dev_warn(&spi->dev, "failed to write CS (%d)\n", ret);
+}

So we never disable chip select?

+	if (tx_buf) {
+		ret = sx1301_write(ssx->parent, ssx->regs + REG_RADIO_X_ADDR, tx_buf ? tx_buf[0] : 0);

This looks confused.  We're in an if (tx_buf) block but there's a use of
the ternery operator that appears to be checking if we have a tx_buf?

+		if (ret) {
+			dev_err(&spi->dev, "SPI radio address write failed\n");
+			return ret;
+		}
+
+		ret = sx1301_write(ssx->parent, ssx->regs + REG_RADIO_X_DATA, (tx_buf && xfr->len >= 2) ? tx_buf[1] : 0);
+		if (ret) {
+			dev_err(&spi->dev, "SPI radio data write failed\n");
+			return ret;
+		}

This looks awfully like you're coming in at the wrong abstraction layer
and the hardware actually implements a register abstraction rather than
a SPI one so you should be using regmap as the abstraction.

+	if (rx_buf) {
+		ret = sx1301_read(ssx->parent, ssx->regs + REG_RADIO_X_DATA_READBACK, &rx_buf[xfr->len - 1]);
+		if (ret) {
+			dev_err(&spi->dev, "SPI radio data read failed\n");
+			return ret;
+		}
+	}

For a read we never set an address?

+static void sx1301_radio_setup(struct spi_controller *ctrl)
+{
+	ctrl->mode_bits = SPI_CS_HIGH | SPI_NO_CS;

This controller has no chip select but we provided a set_cs operation?
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