Jonathan Cameron | c57f1ba | 2009-08-18 18:06:32 +0100 | [diff] [blame] | 1 | IIO Device drivers |
| 2 | |
| 3 | This is not intended to provide a comprehensive guide to writing an |
| 4 | IIO device driver. For further information see the drivers within the |
| 5 | subsystem. |
| 6 | |
| 7 | The crucial structure for device drivers in iio is iio_dev. |
| 8 | |
| 9 | First allocate one using: |
| 10 | |
Jonathan Cameron | 44d8b35 | 2011-05-18 14:42:40 +0100 | [diff] [blame^] | 11 | struct iio_dev *indio_dev = iio_allocate_device(sizeof(struct chip_state)); |
| 12 | where chip_state is a structure of local state data for this instance of |
| 13 | the chip. |
| 14 | |
| 15 | That data can be accessed using iio_priv(struct iio_dev *) |
Jonathan Cameron | c57f1ba | 2009-08-18 18:06:32 +0100 | [diff] [blame] | 16 | |
Amit Kucheria | 51bf00a | 2009-11-09 15:10:15 +0200 | [diff] [blame] | 17 | Then fill in the following: |
Jonathan Cameron | c57f1ba | 2009-08-18 18:06:32 +0100 | [diff] [blame] | 18 | |
Jonathan Cameron | 44d8b35 | 2011-05-18 14:42:40 +0100 | [diff] [blame^] | 19 | - indio_dev->dev.parent |
| 20 | Struct device associated with the underlying hardware. |
| 21 | - indio_dev->name |
| 22 | Name of the device being driven - made available as the name |
| 23 | attribute in sysfs. |
Jonathan Cameron | c57f1ba | 2009-08-18 18:06:32 +0100 | [diff] [blame] | 24 | |
Jonathan Cameron | 44d8b35 | 2011-05-18 14:42:40 +0100 | [diff] [blame^] | 25 | - indio_dev->info |
| 26 | pointer to a structure with elements that tend to be fixed for |
| 27 | large sets of different parts supported by a given driver. |
| 28 | This contains: |
| 29 | * info->driver_module: |
| 30 | Set to THIS_MODULE. Used to ensure correct ownership |
| 31 | of various resources allocate by the core. |
| 32 | * info->num_interrupt_lines: |
| 33 | Number of event triggering hardware lines the device has. |
| 34 | * info->event_attrs: |
| 35 | Attributes used to enable / disable hardware events. |
| 36 | * info->attrs: |
| 37 | General device attributes. Typically used for the weird |
| 38 | and the wonderful bits not covered by the channel specification. |
| 39 | * info->read_raw: |
| 40 | Raw data reading function. Used for both raw channel access |
| 41 | and for associate parameters such as offsets and scales. |
| 42 | * info->write_raw: |
| 43 | Raw value writing function. Used for writable device values such |
| 44 | as DAC values and caliboffset. |
| 45 | * info->read_event_config: |
| 46 | Typically only set if there are some interrupt lines. This |
| 47 | is used to read if an on sensor event detector is enabled. |
| 48 | * info->write_event_config: |
| 49 | Enable / disable an on sensor event detector. |
| 50 | * info->read_event_value: |
| 51 | Read value associated with on sensor event detectors. Note that |
| 52 | the meaning of the returned value is dependent on the event |
| 53 | type. |
| 54 | * info->write_event_value: |
| 55 | Write the value associated with on sensor event detectors. E.g. |
| 56 | a threshold above which an interrupt occurs. Note that the |
| 57 | meaning of the value to be set is event type dependant. |
Jonathan Cameron | c57f1ba | 2009-08-18 18:06:32 +0100 | [diff] [blame] | 58 | |
Jonathan Cameron | 44d8b35 | 2011-05-18 14:42:40 +0100 | [diff] [blame^] | 59 | - indio_dev->modes: |
| 60 | Specify whether direct access and / or ring buffer access is supported. |
| 61 | - indio_dev->ring: |
| 62 | An optional associated buffer. |
| 63 | - indio_dev->pollfunc: |
| 64 | Poll function related elements. This controls what occurs when a trigger |
| 65 | to which this device is attached sends and event. |
| 66 | - indio_dev->channels: |
| 67 | Specification of device channels. Most attributes etc are built |
| 68 | form this spec. |
| 69 | - indio_dev->num_channels: |
| 70 | How many channels are there? |
Jonathan Cameron | c57f1ba | 2009-08-18 18:06:32 +0100 | [diff] [blame] | 71 | |
| 72 | Once these are set up, a call to iio_device_register(indio_dev), |
| 73 | will register the device with the iio core. |
| 74 | |
| 75 | Worth noting here is that, if a ring buffer is to be used, it can be |
| 76 | allocated prior to registering the device with the iio-core, but must |
| 77 | be registered afterwards (otherwise the whole parentage of devices |
| 78 | gets confused) |
| 79 | |
Amit Kucheria | 51bf00a | 2009-11-09 15:10:15 +0200 | [diff] [blame] | 80 | On remove, iio_device_unregister(indio_dev) will remove the device from |
Jonathan Cameron | c57f1ba | 2009-08-18 18:06:32 +0100 | [diff] [blame] | 81 | the core, and iio_free_device will clean up. |