Add support for IIO events #1081

pcercuei · 2023-11-06T11:45:56Z

Add new API functions to allow receiving IIO events.

iio_device_create_event_stream returns a iio_event_stream object, which can then be used to read IIO events;
iio_event_stream_destroy to destroy a previously created stream;
iio_event_stream_read to read an iio_event, either non-blocking (in which case -EAGAIN is returned if there is no event) or blocking (if you want to run it in a thread with a callback mechanism).

The iio_event is the exact same as the iio_event_data object from Linux' <linux/iio/events.h> so the data can be extracted similarly. A few functions were added to make it easier to decode events: iio_event_get_type, iio_event_get_direction, iio_event_get_channel.

Events can be configured (to set thresholds etc.) and enabled/disabled using the standard IIO attribute mechanism, as their settings now appear as standard iio_channel attributes.

rgetz · 2023-11-10T16:07:00Z

don't we want to list that events are possible in iio_info?

pcercuei · 2023-11-10T16:08:55Z

I think I will update iio_info in a separate PR. There are a few things I want to do there anyway, notably handle attribute reads errors better, and add some color.

dlech · 2023-11-14T18:37:34Z

events.c

+}
+
+struct iio_event_stream *
+iio_device_create_event_stream(const struct iio_device *dev)


I have always found it helpful to have the same namespace prefix for all functions in a file. So perhaps this could be iio_event_stream_create_for_device() instead?

That wouldn't be consistent with what we already have, e.g. iio_device_create_buffer, iio_buffer_create_block, iio_buffer_create_stream.

fair enough

dlech · 2023-11-14T18:39:02Z

include/iio/iio.h

+/**
+ * @brief Read an event from the event stream.
+ * @param stream A pointer to an iio_event_stream structure
+ * @out_event An pointer to an iio_event structure, that will be filled by


Suggested change

* @out_event An pointer to an iio_event structure, that will be filled by

* @param out_event An pointer to an iio_event structure, that will be filled by

dlech · 2023-11-14T18:44:24Z

include/iio/iio.h

+static inline enum iio_event_type
+iio_event_get_type(const struct iio_event *event)
+{
+	return (enum iio_event_type)((event->id >> 56) & 0xff);


It could be helpful to mention that this is the equivalent of the IIO_EVENT_CODE_EXTRACT_TYPE macro from linux/iio/events.h.

(same applies to other similar functions here and in the .c file)

Ok, will do.

dlech · 2023-11-14T19:59:38Z

local.c

+	uint64_t event = 1;
+	int ret;
+
+	ret = write(pdata->cancel_fd, &event, sizeof(event));


Should this retry the write on EINTR?

I don't think EINTR can happen at all - the write won't block.

ah yes, of course

dlech · 2023-11-14T20:01:59Z

local.c

+		ret = poll(pollfd, 2, timeout_rel);
+	} while (ret == -1 && errno == EINTR);
+
+	if ((pollfd[1].revents & (POLLIN | POLLNVAL)))


Should this be moved after the ret checks below?

Also, don't we need to read from the eventfd to reset it?

We don't actually want to reset it; otherwise the local_read_event function would only fail the first time.

As for the order - the pollfd[1].revents check is done before the check for ret < 0 just to be consistent with what's already in buffer_check_ready. It shouldn't matter much anyway.

Looking back, I see where the docs say that you have to call iio_event_stream_destroy() to cancel the read, so makes sense now that there is no reset to read again.

dlech · 2023-11-14T20:20:22Z

iio-private.h

@@ -34,7 +34,7 @@
 #define is_little_endian() (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
 #endif

-#define BIT(x) (1 << (x))
+#define BIT(x) (1ull << (x))


Seems odd to make this 64-bit but not the other BIT macros.

I only make the BIT macro able to create 64-bit masks, the BIT_MASK and BIT_WORD still need to work on 32-bit words. I could make them work with 64-bit words, but that means changing the iio_channels_mask struct, which is a bit outside this PR.

Thanks for reviewing btw.

tfcollins · 2023-11-15T16:22:22Z

bindings/python/iio.py

+            chn1 = Channel(dev, _ev_get_channel(_byref(event), dev._device, False))
+            chn2 = Channel(dev, _ev_get_channel(_byref(event), dev._device, True))
+        except Exception:
+            pass


Need to be more explicit for the exception

I changed it to OSError.

rgetz · 2023-11-18T21:04:13Z

@tfcollins should look at the Codacy issues, and point out any that should be fixed before a merge - since they are all Python.

pcercuei · 2023-11-20T16:32:02Z

@tfcollins should look at the Codacy issues, and point out any that should be fixed before a merge - since they are all Python.

I fixed some of them, some other I will leave as-is. The "parent __init__ not called" one because the children class' __init__ just returns an exception (as we don't want to permit direct instantiation), the super() one to be consistent with the rest of the script file.

Add the new iio_chan_type enum entries that were added in kernel v6.7. Signed-off-by: Paul Cercueil <[email protected]>

Add a new API and the corresponding high-level code to support reading and decoding IIO events. Signed-off-by: Paul Cercueil <[email protected]>

Keep a file descriptor to the /dev/iio:deviceX node opened. When creating a buffer, this file descriptor will be duplicated. This ensures that we can create a IIO events file descriptor without having to create a IIO buffer first, and without the problem of trying to open the main FD twice. Signed-off-by: Paul Cercueil <[email protected]>

This allows applications to control the conditions under which IIO events will trigger. Signed-off-by: Paul Cercueil <[email protected]>

Add the necesary callbacks to create an events stream, and read events with the local backend. Signed-off-by: Paul Cercueil <[email protected]>

This can be used to specify the timeout value for a specific communication pipe. Signed-off-by: Paul Cercueil <[email protected]>

Add three new functions tailored for IIO events support. These functions allow to create an IIO events stream, read from it, and close it. The open / close functions use the regular I/O pipe of the responder, while the event read function will use an I/O pipe dedicated to the event stream. This allows the call to be blocking, only returning when an event has been read, without disturbing the command flow. Note that there is no listener thread that would continuously poll the IIO events; those are only read when iiod_client_read_event() is called. This is fine, as IIO events are buffered anyway on the Linux kernel side, so events are not lost. Signed-off-by: Paul Cercueil <[email protected]>

There is no need to have a mutable pointer there, use a const pointer instead. Signed-off-by: Paul Cercueil <[email protected]>

With IIOD's current responder design, we can only answer to a command if we know which I/O pipe is used for answering. This means that if we cannot obtain that information, we cannot answer. In that case, Signed-off-by: Paul Cercueil <[email protected]>

Add support for the IIOD_OP_CREATE_EVSTREAM, IIOD_OP_FREE_EVSTREAM, AND IIOD_OP_READ_EVENT commands. These can be used to open and close event streams, and read events from an event stream. Signed-off-by: Paul Cercueil <[email protected]>

Provide the necesary callbacks to support IIO events with the network backend. Signed-off-by: Paul Cercueil <[email protected]>

Provide the necesary callbacks to support IIO events with the USB backend. Signed-off-by: Paul Cercueil <[email protected]>

Provide the necesary callbacks to support IIO events with the serial backend. Signed-off-by: Paul Cercueil <[email protected]>

The previous commit(s) reworking IIO attributes changed the type of the 'attr' variable from a const string to a 'struct iio_attr *'. It appears that the code was not properly updated at two different spots; update it so that it works properly. Signed-off-by: Paul Cercueil <[email protected]>

This utility program can be used to monitor events sent by a given IIO device. Signed-off-by: Paul Cercueil <[email protected]>

Add support for reading IIO events in the Python bindings. This is done by calling iio.Device.event_stream() using a context manager, which will create an EventStream object, and then use the read() method: dev = ctx.devices["iio:device4"] with dev.event_stream() as evstream: ev = evstream.read() if ev is not None: print("Got event!") else: time.sleep(0.1) The read() method takes a 'nonblock' argument, which defaults to True. Python code can then poll for events regularly. Polling is better, because doing a blocking read does not give any guarantee about when the call will return. Signed-off-by: Paul Cercueil <[email protected]>

mhennerich

LGTM, Thanks!

pcercuei force-pushed the pcercuei/iio-events branch 3 times, most recently from 71881a2 to d75e8c8 Compare November 6, 2023 14:59

pcercuei mentioned this pull request Nov 6, 2023

IIO event handling support #236

Open

pcercuei force-pushed the pcercuei/iio-events branch 6 times, most recently from 65a15e3 to 12a66cd Compare November 8, 2023 10:18

dlech reviewed Nov 14, 2023

View reviewed changes

pcercuei force-pushed the pcercuei/iio-events branch from 12a66cd to a94e552 Compare November 15, 2023 11:47

tfcollins reviewed Nov 15, 2023

View reviewed changes

pcercuei force-pushed the pcercuei/iio-events branch from a94e552 to dcb882e Compare November 16, 2023 10:01

pcercuei force-pushed the pcercuei/iio-events branch 3 times, most recently from a72f1e9 to 6c78814 Compare November 20, 2023 16:25

pcercuei requested review from tfcollins and mhennerich November 20, 2023 16:32

pcercuei added 7 commits November 21, 2023 16:17

iio.h: Add new iio_chan_type entries

be3a5db

Add the new iio_chan_type enum entries that were added in kernel v6.7. Signed-off-by: Paul Cercueil <[email protected]>

Add support for IIO events

5080ab0

Add a new API and the corresponding high-level code to support reading and decoding IIO events. Signed-off-by: Paul Cercueil <[email protected]>

local: Populate channels with new IIO events attributes

600735c

This allows applications to control the conditions under which IIO events will trigger. Signed-off-by: Paul Cercueil <[email protected]>

local: Add callbacks to support events

7ec1936

Add the necesary callbacks to create an events stream, and read events with the local backend. Signed-off-by: Paul Cercueil <[email protected]>

iiod-responder: Add function iiod_io_set_timeout()

81cf38f

This can be used to specify the timeout value for a specific communication pipe. Signed-off-by: Paul Cercueil <[email protected]>

pcercuei added 9 commits November 21, 2023 16:18

iiod: Constify iio_device pointer

a55c644

There is no need to have a mutable pointer there, use a const pointer instead. Signed-off-by: Paul Cercueil <[email protected]>

iiod: Add support for events

7d8851c

Add support for the IIOD_OP_CREATE_EVSTREAM, IIOD_OP_FREE_EVSTREAM, AND IIOD_OP_READ_EVENT commands. These can be used to open and close event streams, and read events from an event stream. Signed-off-by: Paul Cercueil <[email protected]>

network: Add support for IIO events

8bc719f

Provide the necesary callbacks to support IIO events with the network backend. Signed-off-by: Paul Cercueil <[email protected]>

usb: Add support for IIO events

8270801

Provide the necesary callbacks to support IIO events with the USB backend. Signed-off-by: Paul Cercueil <[email protected]>

serial: Add support for IIO events

9916f46

Provide the necesary callbacks to support IIO events with the serial backend. Signed-off-by: Paul Cercueil <[email protected]>

utils: Add 'iio_event' program

94fc363

This utility program can be used to monitor events sent by a given IIO device. Signed-off-by: Paul Cercueil <[email protected]>

pcercuei force-pushed the pcercuei/iio-events branch from 6c78814 to b574558 Compare November 21, 2023 15:18

mhennerich approved these changes Nov 22, 2023

View reviewed changes

pcercuei merged commit 7d97827 into main Nov 22, 2023
23 of 24 checks passed

pcercuei deleted the pcercuei/iio-events branch November 22, 2023 12:42

rgetz mentioned this pull request Nov 27, 2023

Better debug macros and iio_info output #1086

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Add support for IIO events #1081

Add support for IIO events #1081

pcercuei commented Nov 6, 2023

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dlech Nov 14, 2023

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rgetz commented Nov 18, 2023

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	* @out_event An pointer to an iio_event structure, that will be filled by
	* @param out_event An pointer to an iio_event structure, that will be filled by

Add support for IIO events #1081

Add support for IIO events #1081

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pcercuei commented Nov 6, 2023

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rgetz commented Nov 18, 2023

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