[PATCH] Staging: iio: Move evgen interrupt generation to irq_work

From: Cristina Opriceana
Date: Tue Aug 18 2015 - 08:55:30 EST

A more abstract way of handling interrupt generation in the dummy driver
is represented by irq_work which substitutes the irq_chip, used to
provide an IRQ line number. irq_work runs tasks from hardirq context,
but in a NMI-safe environment and deals better with synchronization
problems. An interrupt can be triggered by calling irq_work_queue()
and the work will be performed by a pre-registered handler, which
acts as a callback.

Cc: Daniel Baluta <daniel.baluta@xxxxxxxxx>
Suggested-by: Jonathan Cameron <jic23@xxxxxxxxxx>
Signed-off-by: Cristina Opriceana <cristina.opriceana@xxxxxxxxx>
---
This is the first draft for the irq_work replacement.
As we want to move the iio dummy driver out of staging,
we started to implement Jonathan's suggestions from here:
<http://marc.info/?l=linux-iio&m=142403390705515&w=2>

drivers/staging/iio/iio_dummy_evgen.c | 171 +++++++++-----------------
drivers/staging/iio/iio_dummy_evgen.h | 15 ++-
drivers/staging/iio/iio_simple_dummy.c | 6 +-
drivers/staging/iio/iio_simple_dummy.h | 8 +-
drivers/staging/iio/iio_simple_dummy_events.c | 71 ++++-------
5 files changed, 105 insertions(+), 166 deletions(-)

diff --git a/drivers/staging/iio/iio_dummy_evgen.c b/drivers/staging/iio/iio_dummy_evgen.c
index 6d38854..974ef8a 100644
--- a/drivers/staging/iio/iio_dummy_evgen.c
+++ b/drivers/staging/iio/iio_dummy_evgen.c
@@ -25,132 +25,87 @@
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

-/* Fiddly bit of faking and irq without hardware */
-#define IIO_EVENTGEN_NO 10
-/**
- * struct iio_dummy_evgen - evgen state
- * @chip: irq chip we are faking
- * @base: base of irq range
- * @enabled: mask of which irqs are enabled
- * @inuse: mask of which irqs are connected
- * @regs: irq regs we are faking
- * @lock: protect the evgen state
- */
-struct iio_dummy_eventgen {
- struct irq_chip chip;
- int base;
- bool enabled[IIO_EVENTGEN_NO];
- bool inuse[IIO_EVENTGEN_NO];
- struct iio_dummy_regs regs[IIO_EVENTGEN_NO];
- struct mutex lock;
-};
+static LIST_HEAD(iio_dummy_event_list);
+static DEFINE_MUTEX(iio_dummy_event_list_mutex);

-/* We can only ever have one instance of this 'device' */
-static struct iio_dummy_eventgen *iio_evgen;
-static const char *iio_evgen_name = "iio_dummy_evgen";
-
-static void iio_dummy_event_irqmask(struct irq_data *d)
+struct iio_dummy_event *get_event(int index)
{
- struct irq_chip *chip = irq_data_get_irq_chip(d);
- struct iio_dummy_eventgen *evgen =
- container_of(chip, struct iio_dummy_eventgen, chip);
+ struct list_head *ptr, *tmp;
+ struct iio_dummy_event *iio_event = NULL;

- evgen->enabled[d->irq - evgen->base] = false;
-}
-
-static void iio_dummy_event_irqunmask(struct irq_data *d)
-{
- struct irq_chip *chip = irq_data_get_irq_chip(d);
- struct iio_dummy_eventgen *evgen =
- container_of(chip, struct iio_dummy_eventgen, chip);
-
- evgen->enabled[d->irq - evgen->base] = true;
+ mutex_lock(&iio_dummy_event_list_mutex);
+ list_for_each_safe(ptr, tmp, &iio_dummy_event_list) {
+ iio_event = list_entry(ptr, struct iio_dummy_event, l);
+ if (iio_event->regs.reg_id == index)
+ break;
+ }
+ mutex_unlock(&iio_dummy_event_list_mutex);
+ return iio_event;
}

-static int iio_dummy_evgen_create(void)
+int iio_dummy_evgen_create(struct iio_dev *indio_dev, int index)
{
- int ret, i;
+ struct iio_dummy_event *iio_event;

- iio_evgen = kzalloc(sizeof(*iio_evgen), GFP_KERNEL);
- if (!iio_evgen)
+ iio_event = kzalloc(sizeof(*iio_event), GFP_KERNEL);
+ if (!iio_event)
return -ENOMEM;

- iio_evgen->base = irq_alloc_descs(-1, 0, IIO_EVENTGEN_NO, 0);
- if (iio_evgen->base < 0) {
- ret = iio_evgen->base;
- kfree(iio_evgen);
- return ret;
- }
- iio_evgen->chip.name = iio_evgen_name;
- iio_evgen->chip.irq_mask = &iio_dummy_event_irqmask;
- iio_evgen->chip.irq_unmask = &iio_dummy_event_irqunmask;
- for (i = 0; i < IIO_EVENTGEN_NO; i++) {
- irq_set_chip(iio_evgen->base + i, &iio_evgen->chip);
- irq_set_handler(iio_evgen->base + i, &handle_simple_irq);
- irq_modify_status(iio_evgen->base + i,
- IRQ_NOREQUEST | IRQ_NOAUTOEN,
- IRQ_NOPROBE);
- }
- mutex_init(&iio_evgen->lock);
+ iio_event->dev = indio_dev;
+ iio_event->regs.reg_id = index;
+ mutex_lock(&iio_dummy_event_list_mutex);
+ list_add(&iio_event->l, &iio_dummy_event_list);
+ mutex_unlock(&iio_dummy_event_list_mutex);
+
return 0;
}
+EXPORT_SYMBOL_GPL(iio_dummy_evgen_create);

-/**
- * iio_dummy_evgen_get_irq() - get an evgen provided irq for a device
- *
- * This function will give a free allocated irq to a client device.
- * That irq can then be caused to 'fire' by using the associated sysfs file.
- */
-int iio_dummy_evgen_get_irq(void)
+void iio_dummy_init_work_handler(int index, void (*f)(struct irq_work *))
{
- int i, ret = 0;
-
- if (!iio_evgen)
- return -ENODEV;
+ struct iio_dummy_event *iio_event = get_event(index);

- mutex_lock(&iio_evgen->lock);
- for (i = 0; i < IIO_EVENTGEN_NO; i++)
- if (!iio_evgen->inuse[i]) {
- ret = iio_evgen->base + i;
- iio_evgen->inuse[i] = true;
- break;
- }
- mutex_unlock(&iio_evgen->lock);
- if (i == IIO_EVENTGEN_NO)
- return -ENOMEM;
- return ret;
+ if (iio_event)
+ init_irq_work(&iio_event->work, f);
}
-EXPORT_SYMBOL_GPL(iio_dummy_evgen_get_irq);
+EXPORT_SYMBOL_GPL(iio_dummy_init_work_handler);

-/**
- * iio_dummy_evgen_release_irq() - give the irq back.
- * @irq: irq being returned to the pool
- *
- * Used by client driver instances to give the irqs back when they disconnect
- */
-void iio_dummy_evgen_release_irq(int irq)
+struct iio_dummy_regs *iio_dummy_evgen_get_regs(int index)
{
- mutex_lock(&iio_evgen->lock);
- iio_evgen->inuse[irq - iio_evgen->base] = false;
- mutex_unlock(&iio_evgen->lock);
-}
-EXPORT_SYMBOL_GPL(iio_dummy_evgen_release_irq);
+ struct iio_dummy_event *iio_event;
+ struct iio_dummy_regs *regs = NULL;

-struct iio_dummy_regs *iio_dummy_evgen_get_regs(int irq)
-{
- return &iio_evgen->regs[irq - iio_evgen->base];
+ iio_event = get_event(index);
+ if (!iio_event)
+ goto err_regs;
+
+ regs = &iio_event->regs;
+err_regs:
+ return regs;
}
EXPORT_SYMBOL_GPL(iio_dummy_evgen_get_regs);

-static void iio_dummy_evgen_free(void)
+void iio_dummy_evgen_free(int index)
{
- irq_free_descs(iio_evgen->base, IIO_EVENTGEN_NO);
- kfree(iio_evgen);
+ struct list_head *ptr, *tmp;
+ struct iio_dummy_event *iio_event;
+
+ mutex_lock(&iio_dummy_event_list_mutex);
+ list_for_each_safe(ptr, tmp, &iio_dummy_event_list) {
+ iio_event = list_entry(ptr, struct iio_dummy_event, l);
+ if (iio_event->regs.reg_id == index) {
+ list_del(ptr);
+ kfree(iio_event);
+ break;
+ }
+ }
+ mutex_unlock(&iio_dummy_event_list_mutex);
}
+EXPORT_SYMBOL_GPL(iio_dummy_evgen_free);

+/* Do nothing upon release */
static void iio_evgen_release(struct device *dev)
{
- iio_dummy_evgen_free();
}

static ssize_t iio_evgen_poke(struct device *dev,
@@ -159,6 +114,7 @@ static ssize_t iio_evgen_poke(struct device *dev,
size_t len)
{
struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+ struct iio_dummy_event *iio_event = get_event(this_attr->address);
unsigned long event;
int ret;

@@ -166,12 +122,11 @@ static ssize_t iio_evgen_poke(struct device *dev,
if (ret)
return ret;

- iio_evgen->regs[this_attr->address].reg_id = this_attr->address;
- iio_evgen->regs[this_attr->address].reg_data = event;
-
- if (iio_evgen->enabled[this_attr->address])
- handle_nested_irq(iio_evgen->base + this_attr->address);
-
+ if (iio_event) {
+ iio_event->regs.reg_data = event;
+ /* trigger interrupt */
+ irq_work_queue(&iio_event->work);
+ }
return len;
}

@@ -217,10 +172,6 @@ static struct device iio_evgen_dev = {

static __init int iio_dummy_evgen_init(void)
{
- int ret = iio_dummy_evgen_create();
-
- if (ret < 0)
- return ret;
device_initialize(&iio_evgen_dev);
dev_set_name(&iio_evgen_dev, "iio_evgen");
return device_add(&iio_evgen_dev);
diff --git a/drivers/staging/iio/iio_dummy_evgen.h b/drivers/staging/iio/iio_dummy_evgen.h
index d044b94..b78b1eb 100644
--- a/drivers/staging/iio/iio_dummy_evgen.h
+++ b/drivers/staging/iio/iio_dummy_evgen.h
@@ -1,13 +1,22 @@
#ifndef _IIO_DUMMY_EVGEN_H_
#define _IIO_DUMMY_EVGEN_H_
+#include <linux/irq_work.h>

struct iio_dummy_regs {
u32 reg_id;
u32 reg_data;
};

-struct iio_dummy_regs *iio_dummy_evgen_get_regs(int irq);
-int iio_dummy_evgen_get_irq(void);
-void iio_dummy_evgen_release_irq(int irq);
+struct iio_dummy_event {
+ struct iio_dev *dev;
+ struct iio_dummy_regs regs;
+ struct irq_work work;
+ struct list_head l;
+};
+
+int iio_dummy_evgen_create(struct iio_dev *indio_dev, int index);
+void iio_dummy_init_work_handler(int index, void (*f)(struct irq_work *));
+struct iio_dummy_regs *iio_dummy_evgen_get_regs(int index);
+void iio_dummy_evgen_free(int index);

#endif /* _IIO_DUMMY_EVGEN_H_ */
diff --git a/drivers/staging/iio/iio_simple_dummy.c b/drivers/staging/iio/iio_simple_dummy.c
index 381f90f..1ae082d 100644
--- a/drivers/staging/iio/iio_simple_dummy.c
+++ b/drivers/staging/iio/iio_simple_dummy.c
@@ -635,7 +635,7 @@ static int iio_dummy_probe(int index)
/* Specify that device provides sysfs type interfaces */
indio_dev->modes = INDIO_DIRECT_MODE;

- ret = iio_simple_dummy_events_register(indio_dev);
+ ret = iio_simple_dummy_events_register(indio_dev, index);
if (ret < 0)
goto error_free_device;

@@ -651,7 +651,7 @@ static int iio_dummy_probe(int index)
error_unconfigure_buffer:
iio_simple_dummy_unconfigure_buffer(indio_dev);
error_unregister_events:
- iio_simple_dummy_events_unregister(indio_dev);
+ iio_simple_dummy_events_unregister(index);
error_free_device:
iio_device_free(indio_dev);
error_ret:
@@ -682,7 +682,7 @@ static void iio_dummy_remove(int index)
/* Buffered capture related cleanup */
iio_simple_dummy_unconfigure_buffer(indio_dev);

- iio_simple_dummy_events_unregister(indio_dev);
+ iio_simple_dummy_events_unregister(index);

/* Free all structures */
iio_device_free(indio_dev);
diff --git a/drivers/staging/iio/iio_simple_dummy.h b/drivers/staging/iio/iio_simple_dummy.h
index 8d00224..05b84f7 100644
--- a/drivers/staging/iio/iio_simple_dummy.h
+++ b/drivers/staging/iio/iio_simple_dummy.h
@@ -78,19 +78,19 @@ int iio_simple_dummy_write_event_value(struct iio_dev *indio_dev,
enum iio_event_info info, int val,
int val2);

-int iio_simple_dummy_events_register(struct iio_dev *indio_dev);
-void iio_simple_dummy_events_unregister(struct iio_dev *indio_dev);
+int iio_simple_dummy_events_register(struct iio_dev *indio_dev, int index);
+void iio_simple_dummy_events_unregister(int index);

#else /* Stubs for when events are disabled at compile time */

static inline int
-iio_simple_dummy_events_register(struct iio_dev *indio_dev)
+iio_simple_dummy_events_register(struct iio_dev *indio_dev, int index)
{
return 0;
};

static inline void
-iio_simple_dummy_events_unregister(struct iio_dev *indio_dev)
+iio_simple_dummy_events_unregister(int index)
{ };

#endif /* CONFIG_IIO_SIMPLE_DUMMY_EVENTS*/
diff --git a/drivers/staging/iio/iio_simple_dummy_events.c b/drivers/staging/iio/iio_simple_dummy_events.c
index 73108ba..cf777b1 100644
--- a/drivers/staging/iio/iio_simple_dummy_events.c
+++ b/drivers/staging/iio/iio_simple_dummy_events.c
@@ -155,23 +155,25 @@ int iio_simple_dummy_write_event_value(struct iio_dev *indio_dev,

/**
* iio_simple_dummy_event_handler() - identify and pass on event
- * @irq: irq of event line
- * @private: pointer to device instance state.
+ * @work: struct irq_work which handles interrupt generation
*
* This handler is responsible for querying the device to find out what
* event occurred and for then pushing that event towards userspace.
* Here only one event occurs so we push that directly on with locally
* grabbed timestamp.
*/
-static irqreturn_t iio_simple_dummy_event_handler(int irq, void *private)
+void iio_simple_dummy_event_handler(struct irq_work *work)
{
- struct iio_dev *indio_dev = private;
+ struct iio_dummy_event *iio_event = container_of(work,
+ struct iio_dummy_event,
+ work);
+ struct iio_dev *indio_dev = iio_event->dev;
struct iio_dummy_state *st = iio_priv(indio_dev);

dev_dbg(&indio_dev->dev, "id %x event %x\n",
- st->regs->reg_id, st->regs->reg_data);
+ iio_event->regs.reg_id, iio_event->regs.reg_data);

- switch (st->regs->reg_data) {
+ switch (iio_event->regs.reg_data) {
case 0:
iio_push_event(indio_dev,
IIO_EVENT_CODE(IIO_VOLTAGE, 0, 0,
@@ -209,59 +211,36 @@ static irqreturn_t iio_simple_dummy_event_handler(int irq, void *private)
default:
break;
}
-
- return IRQ_HANDLED;
}

/**
* iio_simple_dummy_events_register() - setup interrupt handling for events
- * @indio_dev: device instance data
+ * @indio_dev: device instance data
+ * @index: integer which identifies the dummy instance
*
- * This function requests the threaded interrupt to handle the events.
- * Normally the irq is a hardware interrupt and the number comes
- * from board configuration files. Here we get it from a companion
- * module that fakes the interrupt for us. Note that module in
- * no way forms part of this example. Just assume that events magically
- * appear via the provided interrupt.
+ * Normally the irq is a hardware interrupt and the number comes from
+ * board configuration files. Here, the interrupt generation is handled
+ * by a companion module that will generate hardware interrupts using
+ * the irq_work API. Note that module in no way forms part of this example.
+ * Just assume that events magically appear via the provided interrupt.
*/
-int iio_simple_dummy_events_register(struct iio_dev *indio_dev)
+int iio_simple_dummy_events_register(struct iio_dev *indio_dev, int index)
{
- struct iio_dummy_state *st = iio_priv(indio_dev);
int ret;

- /* Fire up event source - normally not present */
- st->event_irq = iio_dummy_evgen_get_irq();
- if (st->event_irq < 0) {
- ret = st->event_irq;
- goto error_ret;
- }
- st->regs = iio_dummy_evgen_get_regs(st->event_irq);
-
- ret = request_threaded_irq(st->event_irq,
- NULL,
- &iio_simple_dummy_event_handler,
- IRQF_ONESHOT,
- "iio_simple_event",
- indio_dev);
- if (ret < 0)
- goto error_free_evgen;
+ ret = iio_dummy_evgen_create(indio_dev, index);
+ if (ret)
+ return ret;
+ /* register handler */
+ iio_dummy_init_work_handler(index, iio_simple_dummy_event_handler);
return 0;
-
-error_free_evgen:
- iio_dummy_evgen_release_irq(st->event_irq);
-error_ret:
- return ret;
}

/**
- * iio_simple_dummy_events_unregister() - tidy up interrupt handling on remove
- * @indio_dev: device instance data
+ * iio_simple_dummy_events_unregister()
+ * @index: device instance identification
*/
-void iio_simple_dummy_events_unregister(struct iio_dev *indio_dev)
+void iio_simple_dummy_events_unregister(int index)
{
- struct iio_dummy_state *st = iio_priv(indio_dev);
-
- free_irq(st->event_irq, indio_dev);
- /* Not part of normal driver */
- iio_dummy_evgen_release_irq(st->event_irq);
+ iio_dummy_evgen_free(index);
}
--
1.9.1

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