staging: wfx: add infrastructure for new driver

Instantiate build infrastructure WFx driver. This driver provides support
for Wifi chipset Silicon Labs WF200 and further:

   https://www.silabs.com/documents/public/data-sheets/wf200-datasheet.pdf

This chip support SPI and SDIO bus.

SDIO interface has two particularities:
    1. Some parameters may be useful for end user (I will talk about
       gpio_wakeup later).
    2. The SDIO VID and PID of WF200 are 0000:0001 which are too much
       generic to rely on.

So, current code checks VID/PID and looks for a node in DT (since WF200
targets embedded platforms, I don't think it is a problem to rely on
DT). DT can also be used to define to parameters for driver. Currently,
if no node is found, a warning is emitted, but it could be changed in
error.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20190919142527.31797-2-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/drivers/staging/wfx/bus_spi.c b/drivers/staging/wfx/bus_spi.c
new file mode 100644
index 000000000000..574b60f513e9
--- /dev/null
+++ b/drivers/staging/wfx/bus_spi.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SPI interface.
+ *
+ * Copyright (c) 2017-2019, Silicon Laboratories, Inc.
+ * Copyright (c) 2011, Sagrad Inc.
+ * Copyright (c) 2010, ST-Ericsson
+ */
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/of.h>
+
+#include "bus.h"
+
+static int wfx_spi_probe(struct spi_device *func)
+{
+	return -EIO;
+}
+
+/* Disconnect Function to be called by SPI stack when device is disconnected */
+static int wfx_spi_disconnect(struct spi_device *func)
+{
+	return 0;
+}
+
+/*
+ * For dynamic driver binding, kernel does not use OF to match driver. It only
+ * use modalias and modalias is a copy of 'compatible' DT node with vendor
+ * stripped.
+ */
+static const struct spi_device_id wfx_spi_id[] = {
+	{ "wfx-spi", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(spi, wfx_spi_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id wfx_spi_of_match[] = {
+	{ .compatible = "silabs,wfx-spi" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, wfx_spi_of_match);
+#endif
+
+struct spi_driver wfx_spi_driver = {
+	.driver = {
+		.name = "wfx-spi",
+		.of_match_table = of_match_ptr(wfx_spi_of_match),
+	},
+	.id_table = wfx_spi_id,
+	.probe = wfx_spi_probe,
+	.remove = wfx_spi_disconnect,
+};