staging: iio: resolver: new driver for AD2S90 devices

This also kicks off the new resolver subsection.
Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/Kconfig

@@ -50,6 +50,7 @@ source "drivers/staging/iio/imu/Kconfig"
 source "drivers/staging/iio/light/Kconfig"
 source "drivers/staging/iio/magnetometer/Kconfig"
 source "drivers/staging/iio/meter/Kconfig"
+source "drivers/staging/iio/resolver/Kconfig"
 source "drivers/staging/iio/trigger/Kconfig"
 
 endif # IIO

drivers/staging/iio/Makefile

@@ -19,4 +19,5 @@ obj-y += imu/
 obj-y += light/
 obj-y += magnetometer/
 obj-y += meter/
+obj-y += resolver/
 obj-y += trigger/

drivers/staging/iio/resolver/Kconfig

+#
+# Resolver/Synchro drivers
+#
+comment "Resolver to digital converters"
+
+config AD2S90
+	tristate "Analog Devices ad2s90 driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices spi resolver
+	  to digital converters, ad2s90, provides direct access via sysfs.

drivers/staging/iio/resolver/Makefile

+#
+# Makefile for Resolver/Synchro drivers
+#
+
+obj-$(CONFIG_AD2S90) += ad2s90.o

drivers/staging/iio/resolver/ad2s90.c

+/*
+ * ad2s90.c simple support for the ADI Resolver to Digital Converters: AD2S90
+ *
+ * Copyright (c) 2010-2010 Analog Devices Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+#include "../iio.h"
+#include "../sysfs.h"
+
+#define DRV_NAME "ad2s90"
+
+struct ad2s90_state {
+	struct mutex lock;
+	struct iio_dev *idev;
+	struct spi_device *sdev;
+	u8 rx[2];
+	u8 tx[2];
+};
+
+static ssize_t ad2s90_show_angular(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct spi_message msg;
+	struct spi_transfer xfer;
+	int ret;
+	ssize_t len = 0;
+	u16 val;
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s90_state *st = idev->dev_data;
+
+	xfer.len = 1;
+	xfer.tx_buf = st->tx;
+	xfer.rx_buf = st->rx;
+	mutex_lock(&st->lock);
+
+	spi_message_init(&msg);
+	spi_message_add_tail(&xfer, &msg);
+	ret = spi_sync(st->sdev, &msg);
+	if (ret)
+		goto error_ret;
+	val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
+	len = sprintf(buf, "%d\n", val);
+error_ret:
+	mutex_unlock(&st->lock);
+
+	return ret ? ret : len;
+}
+
+#define IIO_DEV_ATTR_SIMPLE_RESOLVER(_show) \
+	IIO_DEVICE_ATTR(angular, S_IRUGO, _show, NULL, 0)
+
+static IIO_CONST_ATTR(description,
+	"Low Cost, Complete 12-Bit Resolver-to-Digital Converter");
+static IIO_DEV_ATTR_SIMPLE_RESOLVER(ad2s90_show_angular);
+
+static struct attribute *ad2s90_attributes[] = {
+	&iio_const_attr_description.dev_attr.attr,
+	&iio_dev_attr_angular.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ad2s90_attribute_group = {
+	.name = DRV_NAME,
+	.attrs = ad2s90_attributes,
+};
+
+static int __devinit ad2s90_probe(struct spi_device *spi)
+{
+	struct ad2s90_state *st;
+	int ret = 0;
+
+	st = kzalloc(sizeof(*st), GFP_KERNEL);
+	if (st == NULL) {
+		ret = -ENOMEM;
+		goto error_ret;
+	}
+	spi_set_drvdata(spi, st);
+
+	mutex_init(&st->lock);
+	st->sdev = spi;
+
+	st->idev = iio_allocate_device();
+	if (st->idev == NULL) {
+		ret = -ENOMEM;
+		goto error_free_st;
+	}
+	st->idev->dev.parent = &spi->dev;
+	st->idev->num_interrupt_lines = 0;
+	st->idev->event_attrs = NULL;
+
+	st->idev->attrs = &ad2s90_attribute_group;
+	st->idev->dev_data = (void *)(st);
+	st->idev->driver_module = THIS_MODULE;
+	st->idev->modes = INDIO_DIRECT_MODE;
+
+	ret = iio_device_register(st->idev);
+	if (ret)
+		goto error_free_dev;
+
+	/* need 600ns between CS and the first falling edge of SCLK */
+	spi->max_speed_hz = 830000;
+	spi->mode = SPI_MODE_3;
+	spi_setup(spi);
+
+	return 0;
+
+error_free_dev:
+	iio_free_device(st->idev);
+error_free_st:
+	kfree(st);
+error_ret:
+	return ret;
+}
+
+static int __devexit ad2s90_remove(struct spi_device *spi)
+{
+	struct ad2s90_state *st = spi_get_drvdata(spi);
+
+	iio_device_unregister(st->idev);
+	kfree(st);
+
+	return 0;
+}
+
+static struct spi_driver ad2s90_driver = {
+	.driver = {
+		.name = DRV_NAME,
+		.owner = THIS_MODULE,
+	},
+	.probe = ad2s90_probe,
+	.remove = __devexit_p(ad2s90_remove),
+};
+
+static __init int ad2s90_spi_init(void)
+{
+	return spi_register_driver(&ad2s90_driver);
+}
+module_init(ad2s90_spi_init);
+
+static __exit void ad2s90_spi_exit(void)
+{
+	spi_unregister_driver(&ad2s90_driver);
+}
+module_exit(ad2s90_spi_exit);
+
+MODULE_AUTHOR("Graff Yang <graff.yang@gmail.com>");
+MODULE_DESCRIPTION("Analog Devices AD2S90 Resolver to Digital SPI driver");
+MODULE_LICENSE("GPL v2");