[RFC v2 00/11] iio: add iio backend device type

[RFC v2 00/11] iio: add iio backend device type

[Olivier Moysan]

This v2 is an addon to initial RFC:
https://lore.kernel.org/lkml/20230623140944.2613002-1-olivier.moysan@foss.st.com/

Despite the "IIO backend" naming has to be changed (as pointed out by
Jonathan previously), it has been kept here, for time being. The
appropriated naming still has to be discussed later on.

In the previous RFC the "IIO backend" concept was proposed through
a set of template APIs.

This v2 implements a functionnal exemple based on STM32 DFSDM,
to bring scaling support to this peripheral.

Olivier Moysan (11):
  iio: introduce iio backend device
  of: property: add device link support for io-backends
  dt-bindings: iio: stm32-dfsdm-adc: add scaling support
  dt-bindings: iio: adc: add scaling support to sd modulator
  iio: adc: stm32-dfsdm: manage dfsdm as a channel provider
  iio: adc: stm32-dfsdm: adopt generic channel bindings
  iio: adc: stm32-dfsdm: add scaling support to dfsdm
  iio: adc: sd modulator: add scale and offset support
  ARM: dts: stm32: adopt new dfsdm bindings on stm32mp151
  ARM: dts: stm32: add dfsdm pins muxing on stm32mp15
  ARM: dts: stm32: add dfsdm iio support on stm32mp157c-ev

 .../iio/adc/sigma-delta-modulator.yaml        |   9 +-
 .../bindings/iio/adc/st,stm32-dfsdm-adc.yaml  | 189 ++++++------------
 arch/arm/boot/dts/st/stm32mp15-pinctrl.dtsi   |  39 ++++
 arch/arm/boot/dts/st/stm32mp151.dtsi          |  18 +-
 arch/arm/boot/dts/st/stm32mp157c-ev1.dts      |  68 +++++++
 drivers/iio/Makefile                          |   1 +
 drivers/iio/adc/sd_adc_modulator.c            | 106 ++++++++--
 drivers/iio/adc/stm32-dfsdm-adc.c             | 187 +++++++++++------
 drivers/iio/industrialio-backend.c            | 107 ++++++++++
 drivers/of/property.c                         |   2 +
 include/linux/iio/backend.h                   |  56 ++++++
 11 files changed, 561 insertions(+), 221 deletions(-)
 create mode 100644 drivers/iio/industrialio-backend.c
 create mode 100644 include/linux/iio/backend.h

-- 
2.25.1

[RFC v2 01/11] iio: introduce iio backend device

[Olivier Moysan]

Add a new device type in IIO framework.
This backend device does not compute channel attributes and does not expose
them through sysfs, as done typically in iio-rescale frontend device.
Instead, it allows to report information applying to channel
attributes through callbacks. These backend devices can be cascaded
to represent chained components.
An IIO device configured as a consumer of a backend device can compute
the channel attributes of the whole chain.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 drivers/iio/Makefile               |   1 +
 drivers/iio/industrialio-backend.c | 107 +++++++++++++++++++++++++++++
 include/linux/iio/backend.h        |  56 +++++++++++++++
 3 files changed, 164 insertions(+)
 create mode 100644 drivers/iio/industrialio-backend.c
 create mode 100644 include/linux/iio/backend.h

diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 9622347a1c1b..9b59c6ab1738 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -5,6 +5,7 @@
 
 obj-$(CONFIG_IIO) += industrialio.o
 industrialio-y := industrialio-core.o industrialio-event.o inkern.o
+industrialio-$(CONFIG_IIO_BACKEND) += industrialio-backend.o
 industrialio-$(CONFIG_IIO_BUFFER) += industrialio-buffer.o
 industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o
 
diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
new file mode 100644
index 000000000000..7d0625889873
--- /dev/null
+++ b/drivers/iio/industrialio-backend.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0
+/* The industrial I/O core, backend handling functions
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/property.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/backend.h>
+
+static DEFINE_IDA(iio_backend_ida);
+
+#define to_iio_backend(_device) container_of((_device), struct iio_backend, dev)
+
+static void iio_backend_release(struct device *device)
+{
+	struct iio_backend *backend = to_iio_backend(device);
+
+	kfree(backend->name);
+	kfree(backend);
+}
+
+static const struct device_type iio_backend_type = {
+	.release = iio_backend_release,
+	.name = "iio_backend_device",
+};
+
+struct iio_backend *iio_backend_alloc(struct device *parent)
+{
+	struct iio_backend *backend;
+
+	backend = devm_kzalloc(parent, sizeof(*backend), GFP_KERNEL);
+
+	backend->dev.parent = parent;
+	backend->dev.type = &iio_backend_type;
+	backend->dev.bus = &iio_bus_type;
+	device_initialize(&backend->dev);
+
+	return backend;
+};
+EXPORT_SYMBOL(iio_backend_alloc);
+
+void iio_backend_free(struct device *dev)
+{
+	if (dev)
+		put_device(dev);
+}
+EXPORT_SYMBOL(iio_backend_free);
+
+int iio_backend_register(struct iio_backend *backend)
+{
+	struct fwnode_handle *fwnode;
+	int id;
+
+	id = ida_alloc(&iio_backend_ida, GFP_KERNEL);
+	if (id < 0)
+		return id;
+	backend->id = id;
+
+	dev_set_name(&backend->dev, "backend%d", backend->id);
+
+	if (dev_fwnode(&backend->dev))
+		fwnode = dev_fwnode(&backend->dev);
+	else
+		fwnode = dev_fwnode(backend->dev.parent);
+	device_set_node(&backend->dev, fwnode);
+
+	return device_add(&backend->dev);
+};
+EXPORT_SYMBOL(iio_backend_register);
+
+void iio_backend_unregister(struct iio_backend *backend)
+{
+	device_del(&backend->dev);
+};
+EXPORT_SYMBOL(iio_backend_unregister);
+
+struct iio_backend *fwnode_iio_backend_get(struct fwnode_handle *fwnode, int index)
+{
+	struct iio_backend *backend;
+	struct fwnode_reference_args iiospec;
+	struct device *bdev;
+	int ret;
+
+	if (index < 0)
+		return ERR_PTR(-EINVAL);
+
+	ret = fwnode_property_get_reference_args(fwnode, "io-backends",
+						 "#io-backend-cells", 0,
+						 index, &iiospec);
+	if (ret)
+		return ERR_PTR(ret);
+
+	bdev = bus_find_device_by_fwnode(&iio_bus_type, iiospec.fwnode);
+	if (!bdev) {
+		fwnode_handle_put(iiospec.fwnode);
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
+	backend = to_iio_backend(bdev);
+
+	fwnode_handle_put(iiospec.fwnode);
+
+	return backend;
+};
+EXPORT_SYMBOL(fwnode_iio_backend_get);
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
new file mode 100644
index 000000000000..d90d345a4625
--- /dev/null
+++ b/include/linux/iio/backend.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * The industrial I/O core, backend handling functions
+ *
+ * Author: Olivier Moysan <olivier.moysan@foss.st.com>.
+ */
+
+#ifndef _IIO_BACKEND_H_
+#define _IIO_BACKEND_H_
+#include <linux/iio/iio.h>
+
+struct iio_backend_ops;
+struct iio_backend;
+
+/**
+ * struct iio_backend_ops - operations structure for an iio_backend
+ * @enable:	switch on backend
+ * @disable:	switch off backend
+ * @read_raw:	read data from backend
+ **/
+struct iio_backend_ops {
+	int (*enable)(struct iio_backend *backend);
+	int (*disable)(struct iio_backend *backend);
+	int (*read_raw)(struct iio_backend *backend, int *val, int *val2, long mask);
+};
+
+/**
+ * truct iio_backend - industrial I/O backend device
+ * @ops:	operations structure
+ * @module:	owner of this driver module
+ * @id:		unique id number
+ * @name:	unique name
+ * @dev:	associated device
+ * @priv:	private data pointer
+ **/
+struct iio_backend {
+	const struct iio_backend_ops	*ops;
+	struct module			*owner;
+	int				id;
+	const char			*name;
+	struct device			dev;
+	struct list_head		list;
+	void				*priv;
+};
+
+struct iio_backend *iio_backend_alloc(struct device *parent);
+
+void iio_backend_free(struct device *dev);
+
+int iio_backend_register(struct iio_backend *backend);
+
+void iio_backend_unregister(struct iio_backend *backend);
+
+struct iio_backend *fwnode_iio_backend_get(struct fwnode_handle *fwnode, int index);
+
+#endif /* _IIO_BACKEND_H_ */
-- 
2.25.1

[RFC v2 00/11] iio: add iio backend device type

[Olivier Moysan]

This v2 is an addon to initial RFC:
https://lore.kernel.org/lkml/20230623140944.2613002-1-olivier.moysan@foss.st.com/

Despite the "IIO backend" naming has to be changed (as pointed out by
Jonathan previously), it has been kept here, for time being. The
appropriated naming still has to be discussed later on.

In the previous RFC the "IIO backend" concept was proposed through
a set of template APIs.

This v2 implements a functionnal exemple based on STM32 DFSDM,
to bring scaling support to this peripheral.

Olivier Moysan (11):
  iio: introduce iio backend device
  of: property: add device link support for io-backends
  dt-bindings: iio: stm32-dfsdm-adc: add scaling support
  dt-bindings: iio: adc: add scaling support to sd modulator
  iio: adc: stm32-dfsdm: manage dfsdm as a channel provider
  iio: adc: stm32-dfsdm: adopt generic channel bindings
  iio: adc: stm32-dfsdm: add scaling support to dfsdm
  iio: adc: sd modulator: add scale and offset support
  ARM: dts: stm32: adopt new dfsdm bindings on stm32mp151
  ARM: dts: stm32: add dfsdm pins muxing on stm32mp15
  ARM: dts: stm32: add dfsdm iio support on stm32mp157c-ev

 .../iio/adc/sigma-delta-modulator.yaml        |   9 +-
 .../bindings/iio/adc/st,stm32-dfsdm-adc.yaml  | 189 ++++++------------
 arch/arm/boot/dts/st/stm32mp15-pinctrl.dtsi   |  39 ++++
 arch/arm/boot/dts/st/stm32mp151.dtsi          |  18 +-
 arch/arm/boot/dts/st/stm32mp157c-ev1.dts      |  68 +++++++
 drivers/iio/Makefile                          |   1 +
 drivers/iio/adc/sd_adc_modulator.c            | 106 ++++++++--
 drivers/iio/adc/stm32-dfsdm-adc.c             | 187 +++++++++++------
 drivers/iio/industrialio-backend.c            | 107 ++++++++++
 drivers/of/property.c                         |   2 +
 include/linux/iio/backend.h                   |  56 ++++++
 11 files changed, 561 insertions(+), 221 deletions(-)
 create mode 100644 drivers/iio/industrialio-backend.c
 create mode 100644 include/linux/iio/backend.h

-- 
2.25.1