staging: iio: adc: Enable driver support for ad7887 AD converter

Enable support for AD7887:  SPI Micropower, 2-Channel, 125 kSPS, 12-Bit ADC

staging: iio: adc: Fix according to review feedback

Review feedback by Jonathan Cameron:
	Combine statements.
	Document struct members.
	Remove redundant variable initialization.
	Simplify multichannel scan from ring logic.
	Fix coding style.

[v2]
staging: iio: adc: ad7887: Fix typos

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>

1 files changed, 105 insertions, 0 deletions

diff --git a/drivers/staging/iio/adc/ad7887.h b/drivers/staging/iio/adc/ad7887.h
new file mode 100644
index 00000000000..8c2a218c949
--- /dev/null
+++ b/drivers/staging/iio/adc/ad7887.h
@@ -0,0 +1,105 @@
+/*
+ * AD7887 SPI ADC driver
+ *
+ * Copyright 2010 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+#ifndef IIO_ADC_AD7887_H_
+#define IIO_ADC_AD7887_H_
+
+#define AD7887_REF_DIS          (1 << 5) /* on-chip reference disable */
+#define AD7887_DUAL             (1 << 4) /* dual-channel mode */
+#define AD7887_CH_AIN1          (1 << 3) /* convert on channel 1, DUAL=1 */
+#define AD7887_CH_AIN0          (0 << 3) /* convert on channel 0, DUAL=0,1 */
+#define AD7887_PM_MODE1         (0)      /* CS based shutdown */
+#define AD7887_PM_MODE2         (1)      /* full on */
+#define AD7887_PM_MODE3         (2)      /* auto shutdown after conversion */
+#define AD7887_PM_MODE4         (3)      /* standby mode */
+
+enum ad7887_channels {
+        AD7887_CH0,
+        AD7887_CH0_CH1,
+        AD7887_CH1,
+};
+
+#define RES_MASK(bits)  ((1 << (bits)) - 1) /* TODO: move this into a common header */
+
+/*
+ * TODO: struct ad7887_platform_data needs to go into include/linux/iio
+ */
+
+struct ad7887_platform_data {
+        /* External Vref voltage applied */
+        u16                             vref_mv;
+        /*
+         * AD7887:
+         * In single channel mode en_dual = flase, AIN1/Vref pins assumes its
+         * Vref function. In dual channel mode en_dual = true, AIN1 becomes the
+         * second input channel, and Vref is internally connected to Vdd.
+         */
+        bool                            en_dual;
+        /*
+         * AD7887:
+         * use_onchip_ref = true, the Vref is internally connected to the 2.500V
+         * Voltage reference. If use_onchip_ref = false, the reference voltage
+         * is supplied by AIN1/Vref
+         */
+        bool                            use_onchip_ref;
+};
+
+struct ad7887_chip_info {
+        u8                              bits;           /* number of ADC bits */
+        u8                              storagebits;    /* number of bits read from the ADC */
+        u8                              left_shift;     /* number of bits the sample must be shifted */
+        char                            sign;           /* [s]igned or [u]nsigned */
+        u16                             int_vref_mv;    /* internal reference voltage */
+};
+
+struct ad7887_state {
+        struct iio_dev                  *indio_dev;
+        struct spi_device               *spi;
+        const struct ad7887_chip_info   *chip_info;
+        struct regulator                *reg;
+        struct work_struct              poll_work;
+        atomic_t                        protect_ring;
+        u16                             int_vref_mv;
+        bool                            en_dual;
+        struct spi_transfer             xfer[4];
+        struct spi_message              msg[3];
+        struct spi_message              *ring_msg;
+        unsigned char                   tx_cmd_buf[8];
+
+        /*
+         * DMA (thus cache coherency maintenance) requires the
+         * transfer buffers to live in their own cache lines.
+         */
+
+        unsigned char                   data[4] ____cacheline_aligned;
+};
+
+enum ad7887_supported_device_ids {
+        ID_AD7887
+};
+
+#ifdef CONFIG_IIO_RING_BUFFER
+int ad7887_scan_from_ring(struct ad7887_state *st, long mask);
+int ad7887_register_ring_funcs_and_init(struct iio_dev *indio_dev);
+void ad7887_ring_cleanup(struct iio_dev *indio_dev);
+#else /* CONFIG_IIO_RING_BUFFER */
+static inline int ad7887_scan_from_ring(struct ad7887_state *st, long mask)
+{
+        return 0;
+}
+
+static inline int
+ad7887_register_ring_funcs_and_init(struct iio_dev *indio_dev)
+{
+        return 0;
+}
+
+static inline void ad7887_ring_cleanup(struct iio_dev *indio_dev)
+{
+}
+#endif /* CONFIG_IIO_RING_BUFFER */
+#endif /* IIO_ADC_AD7887_H_ */