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Date: Thu, 3 Sep 2015 16:51:06 +0300
From: Cristina Georgiana Opriceana <cristina.opriceana@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Daniel Baluta <daniel.baluta@...el.com>,
octavian.purdila@...el.com, Hartmut Knaack <knaack.h@....de>,
Lars-Peter Clausen <lars@...afoo.de>,
Peter Meerwald <pmeerw@...erw.net>,
"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: iio: Move evgen interrupt generation to irq_work
On Mon, Aug 31, 2015 at 6:43 PM, Jonathan Cameron <jic23@...nel.org> wrote:
> On 18/08/15 13:55, Cristina Opriceana wrote:
>> 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@...el.com>
>> Suggested-by: Jonathan Cameron <jic23@...nel.org>
>> Signed-off-by: Cristina Opriceana <cristina.opriceana@...il.com>
> Hi Cristina,
>
> Sorry for the slow response on this!
>
> Anyhow, my main thought here is whether we can take advantage of the irq
> work approach to allow a true simulation of an irq chip rather than
> using the nested_irq as in the original.
>
> The suggestion in that original email was just to move from the 'naughty'
> nested_irq call over to irq work, I wasn't suggesting dropping the irq chip.
Some questions below.
> The aim of this is to allow the dummy driver to fully support
> anything that can be done in a normal driver, without it being in anyway
> modified in form from that of a normal hardware driver.
>
> The result of the change here is to move the actual example code
> futher from a normal driver rather than nearer to it...
Totally agree on this, it does not reflect the code one would write in
a normal driver. I designed it to be more like iio-trig-sysfs as I
thought you suggested and left this aspect behind.
> Sorry for the confusion on this,
I'll redo it, thanks for answering !
Cristina
> Jonathan
>> ---
>> 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);
This will be subsituted with a call of irq_work_queue() which triggers
an interrupt.
>> -
>> + 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,
> It's this null that I never liked. The one thing you 'always'
> do on an event is grab a timestamp in the top half handler. With
> the nested irq handler we could never do that (as not in irq context).
In my approach, the handler run on the irq_work would be initialized
here with iio_simple_dummy_event_handler and replace the
request_threaded_irq() call. Are you suggesting to keep the
request_threaded_irq() call also?
>> - &iio_simple_dummy_event_handler,
Then, what should be run on the irq_work handler? Maybe initialize the
irq_work with this handler and keep the request_threaded_irq call just
formal?
>> - 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);
>> }
>>
>
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