staging: iio: adc: ad7476 new SPI ADC driver

New driver handling:
	AD7475, AD7476, AD7477, AD7478, AD7466, AD7467, AD7468, AD7495
SPI micropower and high speed 12-/10-/8-Bit ADCs

staging: iio: adc: ad7476 apply list review feedback by Jonathan Cameron

Changes since last RFC post V1:
	Mainly list review feedback by Jonathan Cameron

-Remove scan_attrs from chip info structure.
-Remove name from chip info structure, use new spi_device_id instead.
-Allow transfer buffers to live in their own cache lines, to avoid DMA/cache coherency issues.
-Move scan el code into the ring buffer file.
-Use helper function to alloc the pollfunc.
-Use regulator framework and get vref_mv from the regulator in case not specified by pdata.
-Devices with buit-in reference use vref from the chip info structure
-Don't error on missing platform_data

-Make vref_mv type unsigned short
-Print in_scale "Vref / 2^(bits)" if fractional.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/adc/Kconfig

@@ -46,3 +46,14 @@ config AD799X_RING_BUFFER
 	help
 	  Say yes here to include ring buffer support in the AD799X
 	  ADC driver.
+
+config AD7476
+	tristate "Analog Devices AD7475/6/7/8 AD7466/7/8 and AD7495 ADC driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices AD7475/6/7/8,
+	  AD7466/7/8 and AD7495 ADC driver.
+	  If unsure, say N (but it's safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7476.

drivers/staging/iio/adc/Makefile

@@ -10,3 +10,7 @@ obj-$(CONFIG_MAX1363) += max1363.o
 ad799x-y := ad799x_core.o
 ad799x-$(CONFIG_AD799X_RING_BUFFER) += ad799x_ring.o
 obj-$(CONFIG_AD799X) += ad799x.o
+
+ad7476-y := ad7476_core.o
+ad7476-$(CONFIG_IIO_RING_BUFFER) += ad7476_ring.o
+obj-$(CONFIG_AD7476) += ad7476.o

drivers/staging/iio/adc/ad7476.h

@@ -0,0 +1,79 @@
+/*
+ * AD7476/5/7/8 (A) SPI ADC driver
+ *
+ * Copyright 2010 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+#ifndef IIO_ADC_AD7476_H_
+#define IIO_ADC_AD7476_H_
+
+#define RES_MASK(bits)	((1 << (bits)) - 1)
+
+/*
+ * TODO: struct ad7476_platform_data needs to go into include/linux/iio
+ */
+
+struct ad7476_platform_data {
+	u16				vref_mv;
+};
+
+struct ad7476_chip_info {
+	u8				bits;
+	u8				storagebits;
+	u8				res_shift;
+	char				sign;
+	u16				int_vref_mv;
+};
+
+struct ad7476_state {
+	struct iio_dev			*indio_dev;
+	struct spi_device		*spi;
+	const struct ad7476_chip_info	*chip_info;
+	struct regulator		*reg;
+	struct work_struct		poll_work;
+	atomic_t			protect_ring;
+	u16				int_vref_mv;
+	struct spi_transfer		xfer;
+	struct spi_message		msg;
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	unsigned char			data[2] ____cacheline_aligned;
+};
+
+enum ad7476_supported_device_ids {
+	ID_AD7466,
+	ID_AD7467,
+	ID_AD7468,
+	ID_AD7475,
+	ID_AD7476,
+	ID_AD7477,
+	ID_AD7478,
+	ID_AD7495
+};
+
+#ifdef CONFIG_IIO_RING_BUFFER
+int ad7476_scan_from_ring(struct ad7476_state *st);
+int ad7476_register_ring_funcs_and_init(struct iio_dev *indio_dev);
+void ad7476_ring_cleanup(struct iio_dev *indio_dev);
+#else /* CONFIG_IIO_RING_BUFFER */
+static inline ssize_t ad7476_scan_from_ring(struct device *dev,
+					     struct device_attribute *attr,
+					     char *buf)
+{
+	return 0;
+}
+
+static inline int
+ad7476_register_ring_funcs_and_init(struct iio_dev *indio_dev)
+{
+	return 0;
+}
+
+static inline void ad7476_ring_cleanup(struct iio_dev *indio_dev)
+{
+}
+#endif /* CONFIG_IIO_RING_BUFFER */
+#endif /* IIO_ADC_AD7476_H_ */