iio: Add IIO support for the DAC on the Apex Embedded Systems STX104

The Apex Embedded Systems STX104 is a 16-channel 16-bit analog input and 2-channel 16-bit analog output PC/104 card. The STX104 incorporates a large one mega-sample FIFO.

This driver provides IIO support for the 2-channel DAC on the STX104. The base port address for the device may be configured via the stx104_base module parameter.

Signed-off-by William Breathitt Gray <[email protected]>

---
 MAINTAINERS              |   6 ++
 drivers/iio/dac/Kconfig  |   8 +++
 drivers/iio/dac/Makefile |   1 +
 drivers/iio/dac/stx104.c | 178 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 193 insertions(+)
 create mode 100644 drivers/iio/dac/stx104.c

MAINTAINERS +6 -0

index 6ddb488..3905b31 100644
@@ -763,6 +763,12 @@ L:	[email protected] (moderated for non-subscribers)
 S:	Maintained
 F:	sound/aoa/
 
+APEX EMBEDDED SYSTEMS STX104 DAC DRIVER
+M:	William Breathitt Gray <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	drivers/iio/dac/stx104.c
+
 APM DRIVER
 M:	Jiri Kosina <[email protected]>
 S:	Odd fixes

drivers/iio/dac/Kconfig +0 -0

index 5dc7150..85295b1 100644
@@ -206,4 +206,12 @@ config MCP4922
 	  To compile this driver as a module, choose M here: the module

drivers/iio/dac/Kconfig +0 -0

 endmenu

drivers/iio/dac/Makefile +1 -0

index cb525b5..e2deda9 100644
@@ -22,3 +22,4 @@ obj-$(CONFIG_MAX517) += max517.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
 obj-$(CONFIG_MCP4922) += mcp4922.o
+obj-$(CONFIG_STX104) += stx104.o

drivers/iio/dac/stx104.c new file +20 -0

new file mode 100644
index 0000000..3a887ae
@@ -0,0 +1,178 @@
+/*
+ * DAC driver for the Apex Embedded Systems STX104
+ * Copyright (C) 2016 William Breathitt Gray
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/io.h>
+#include <linux/ioport.h>

drivers/iio/dac/stx104.c new file +54 -0

+	.indexed = 1,					\
+	.output = 1					\
+}
+
+static unsigned stx104_base;
+module_param(stx104_base, uint, 0);
+MODULE_PARM_DESC(stx104_base, "Apex Embedded Systems STX104 base address");
+
+/**
+ * struct stx104_iio - IIO device private data structure
+ * @chan_out_states:	channels' output states
+ * @base:		base port address of the IIO device
+ */
+struct stx104_iio {
+	unsigned chan_out_states[STX104_NUM_CHAN];
+	unsigned base;
+};
+
+static int stx104_read_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
+{
+	struct stx104_iio *const priv = iio_priv(indio_dev);
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	*val = priv->chan_out_states[chan->channel];
+
+	return IIO_VAL_INT;
+}
+
+static int stx104_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	struct stx104_iio *const priv = iio_priv(indio_dev);
+	const unsigned chan_addr_offset = 2 * chan->channel;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	priv->chan_out_states[chan->channel] = val;
+	outw(val, priv->base + 4 + chan_addr_offset);
+
+	return 0;
+}
+
+static const struct iio_info stx104_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = stx104_read_raw,
+	.write_raw = stx104_write_raw
+};
+
+static const struct iio_chan_spec stx104_channels[STX104_NUM_CHAN] = {
+	STX104_CHAN(0),

drivers/iio/dac/stx104.c new file +24 -0

+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	if (!devm_request_region(dev, stx104_base, extent, name)) {
+		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
+			stx104_base, stx104_base + extent);
+		return -EBUSY;
+	}
+
+	indio_dev->info = &stx104_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = stx104_channels;
+	indio_dev->num_channels = STX104_NUM_CHAN;
+	indio_dev->name = name;
+
+	priv = iio_priv(indio_dev);
+	priv->base = stx104_base;
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	/* initialize DAC output to 0V */
+	outw(0, stx104_base + 4);

drivers/iio/dac/stx104.c new file +8 -0

+
+static struct platform_driver stx104_driver = {
+	.driver = {
+		.name = "stx104"
+	},
+	.remove = stx104_remove
+};
+

drivers/iio/dac/stx104.c new file +27 -0

+	stx104_device = platform_device_alloc(stx104_driver.driver.name, -1);
+	if (!stx104_device)
+		return -ENOMEM;
+
+	err = platform_device_add(stx104_device);
+	if (err)
+		goto err_platform_device;
+
+	err = platform_driver_probe(&stx104_driver, stx104_probe);
+	if (err)
+		goto err_platform_driver;
+
+	return 0;
+
+err_platform_driver:
+	platform_device_del(stx104_device);
+err_platform_device:
+	platform_device_put(stx104_device);
+	return err;
+}
+
+module_init(stx104_init);
+module_exit(stx104_exit);
+
+MODULE_AUTHOR("William Breathitt Gray <[email protected]>");
+MODULE_DESCRIPTION("Apex Embedded Systems STX104 DAC driver");
+MODULE_LICENSE("GPL v2");

Quoted 7 lines · William Breathitt Gray

The Apex Embedded Systems STX104 is a 16-channel 16-bit analog input and 2-channel 16-bit analog output PC/104 card. The STX104 incorporates a large one mega-sample FIFO.

This driver provides IIO support for the 2-channel DAC on the STX104. The base port address for the device may be configured via the stx104_base module parameter.

Nice looking product.

Quoted 2 lines

Signed-off-by William Breathitt Gray <[email protected]>

I'm a little out of my depth wrt to the lack of discoverability of this so perhaps take comments related to that rather more loosely than the IIO stuff.

Again, module parameter usage will restrict you to instantiating only one instance. Strikes me as a device where you might want more than one. Does the hardware prevent this for some reason?

drivers/iio/dac/stx104.c line 30

Quoted 4 lines

drivers/iio/dac/stx104.c new file +4 -0

+#define STX104_CHAN(chan) {				\
+	.type = IIO_VOLTAGE,				\
+	.channel = chan,				\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\

No information available on scale?

drivers/iio/dac/stx104.c line 94

Quoted 1 line

drivers/iio/dac/stx104.c new file +1 -0

+	const char *const name = dev_name(dev);

Personally I'd not bother with the local name variable but just use dev_name(dev) inline.

drivers/iio/dac/stx104.c line 128

Quoted 5 lines

drivers/iio/dac/stx104.c new file +5 -0

+static int stx104_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+
+	iio_device_unregister(indio_dev);

If there really is nothing to be done other than unregister, then use devm_iio_device_register(...) and you can drop the remove entirely.

Quoted 2 lines · Jonathan Cameron

Quoted 1 line · William Breathitt Gray

The Apex Embedded Systems STX104 is a 16-channel 16-bit analog input

and

Quoted 1 line

Quoted 1 line

2-channel 16-bit analog output PC/104 card. The STX104 incorporates

a

Quoted 3 lines

Quoted 3 lines

large one mega-sample FIFO.

This driver provides IIO support for the 2-channel DAC on the

STX104.

Quoted 8 lines

Quoted 2 lines

The base port address for the device may be configured via the stx104_base module parameter.

Nice looking product.

Quoted 2 lines

Signed-off-by William Breathitt Gray <[email protected]>

I'm a little out of my depth wrt to the lack of discoverability of this so perhaps take comments related to that rather more loosely than the IIO stuff.

Unfortunately, the Apex Embedded Systems STX104 lacks hardware discoverability functionality; users are expected to manually set the base address of the card via physical jumpers, then point their software
to match the set base address of the card.

Quoted 2 lines

Again, module parameter usage will restrict you to instantiating only one instance. Strikes me as a device where you might want more than

one.

Quoted 1 line

Does the hardware prevent this for some reason?

That is a good point; I overlooked the fact that my current implementation restricts the module to only one instance. Since PC/104 cards are effectively ISA cards, instead of the platform driver I will reimplement the module to use the ISA bus driver provided in the linux/isa.h file. I will also allow users to pass in a list of base addresses in order to support multiple instances.

Quoted 6 lines

drivers/iio/dac/stx104.c line 30

Quoted 5 lines

drivers/iio/dac/stx104.c new file +4 -0

+#define STX104_CHAN(chan) {				\
+	.type = IIO_VOLTAGE,				\
+	.channel = chan,				\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\

No information available on scale?

I'm relatively new to the IIO subsystem, so let me know if I
misunderstood: the scale member allows users to view what output range the device is set to use. The Apex Embedded Systems STX104 may be set to
one of four output voltage range modes: +-10V, +-5V, 0-10V, and 0-5V. Unfortunately, these modes are configured via physical jumpers on the card -- and because the card provides no hardware functionality to probe
for its configuration, the scale member should not be set since any value would be at best a guess.

Quoted 4 lines

drivers/iio/dac/stx104.c line 94

Quoted 2 lines

drivers/iio/dac/stx104.c new file +1 -0

+	const char *const name = dev_name(dev);

Personally I'd not bother with the local name variable but just use dev_name(dev) inline.

I'll incorporate this change in version 2 of this patch.

Quoted 7 lines

drivers/iio/dac/stx104.c line 128

Quoted 5 lines

drivers/iio/dac/stx104.c new file +5 -0

+static int stx104_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+
+	iio_device_unregister(indio_dev);

If there really is nothing to be done other than unregister, then use devm_iio_device_register(...) and you can drop the remove

entirely.

Thanks, I wasn't aware of the devm_iio_device_register call! I'll incorporate this change in version 2 of this patch.

William Breathitt Gray