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authorLinus Torvalds <torvalds@linux-foundation.org>2025-01-27 16:51:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2025-01-27 16:51:51 -0800
commit13845bdc869f136f92ad3d40ea09b867bb4ce467 (patch)
treea2f503e60579cee485c2d0de06ad4bcb8abb7612 /Documentation/driver-api
parent125ca745467d4f87ae58e671a4a5714e024d2908 (diff)
parent970b9757cb44c315b5c3da6b1b35a1ffb07cca5a (diff)
Merge tag 'char-misc-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
Pull Char/Misc/IIO driver updates from Greg KH: "Here is the "big" set of char/misc/iio and other smaller driver subsystem updates for 6.14-rc1. Loads of different things in here this development cycle, highlights are: - ntsync "driver" to handle Windows locking types enabling Wine to work much better on many workloads (i.e. games). The driver framework was in 6.13, but now it's enabled and fully working properly. Should make many SteamOS users happy. Even comes with tests! - Large IIO driver updates and bugfixes - FPGA driver updates - Coresight driver updates - MHI driver updates - PPS driver updatesa - const bin_attribute reworking for many drivers - binder driver updates - smaller driver updates and fixes All of these have been in linux-next for a while with no reported issues" * tag 'char-misc-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (311 commits) ntsync: Fix reference leaks in the remaining create ioctls. spmi: hisi-spmi-controller: Drop duplicated OF node assignment in spmi_controller_probe() spmi: Set fwnode for spmi devices ntsync: fix a file reference leak in drivers/misc/ntsync.c scripts/tags.sh: Don't tag usages of DECLARE_BITMAP dt-bindings: interconnect: qcom,msm8998-bwmon: Add SM8750 CPU BWMONs dt-bindings: interconnect: OSM L3: Document sm8650 OSM L3 compatible dt-bindings: interconnect: qcom-bwmon: Document QCS615 bwmon compatibles interconnect: sm8750: Add missing const to static qcom_icc_desc memstick: core: fix kernel-doc notation intel_th: core: fix kernel-doc warnings binder: log transaction code on failure iio: dac: ad3552r-hs: clear reset status flag iio: dac: ad3552r-common: fix ad3541/2r ranges iio: chemical: bme680: Fix uninitialized variable in __bme680_read_raw() misc: fastrpc: Fix copy buffer page size misc: fastrpc: Fix registered buffer page address misc: fastrpc: Deregister device nodes properly in error scenarios nvmem: core: improve range check for nvmem_cell_write() nvmem: qcom-spmi-sdam: Set size in struct nvmem_config ...
Diffstat (limited to 'Documentation/driver-api')
-rw-r--r--Documentation/driver-api/extcon.rst255
-rw-r--r--Documentation/driver-api/index.rst1
-rw-r--r--Documentation/driver-api/pps.rst40
3 files changed, 296 insertions, 0 deletions
diff --git a/Documentation/driver-api/extcon.rst b/Documentation/driver-api/extcon.rst
new file mode 100644
index 000000000000..d3217b9cdcd5
--- /dev/null
+++ b/Documentation/driver-api/extcon.rst
@@ -0,0 +1,255 @@
+=======================
+Extcon Device Subsystem
+=======================
+
+Overview
+========
+
+The Extcon (External Connector) subsystem provides a unified framework for
+managing external connectors in Linux systems. It allows drivers to report
+the state of external connectors and provides a standardized interface for
+userspace to query and monitor these states.
+
+Extcon is particularly useful in modern devices with multiple connectivity
+options, such as smartphones, tablets, and laptops. It helps manage various
+types of connectors, including:
+
+1. USB connectors (e.g., USB-C, micro-USB)
+2. Charging ports (e.g., fast charging, wireless charging)
+3. Audio jacks (e.g., 3.5mm headphone jack)
+4. Video outputs (e.g., HDMI, DisplayPort)
+5. Docking stations
+
+Real-world examples:
+
+1. Smartphone USB-C port:
+ A single USB-C port on a smartphone can serve multiple functions. Extcon
+ can manage the different states of this port, such as:
+ - USB data connection
+ - Charging (various types like fast charging, USB Power Delivery)
+ - Audio output (USB-C headphones)
+ - Video output (USB-C to HDMI adapter)
+
+2. Laptop docking station:
+ When a laptop is connected to a docking station, multiple connections are
+ made simultaneously. Extcon can handle the state changes for:
+ - Power delivery
+ - External displays
+ - USB hub connections
+ - Ethernet connectivity
+
+3. Wireless charging pad:
+ Extcon can manage the state of a wireless charging connection, allowing
+ the system to respond appropriately when a device is placed on or removed
+ from the charging pad.
+
+4. Smart TV HDMI ports:
+ In a smart TV, Extcon can manage multiple HDMI ports, detecting when
+ devices are connected or disconnected, and potentially identifying the
+ type of device (e.g., gaming console, set-top box, Blu-ray player).
+
+The Extcon framework simplifies the development of drivers for these complex
+scenarios by providing a standardized way to report and query connector
+states, handle mutually exclusive connections, and manage connector
+properties. This allows for more robust and flexible handling of external
+connections in modern devices.
+
+Key Components
+==============
+
+extcon_dev
+----------
+
+The core structure representing an Extcon device::
+
+ struct extcon_dev {
+ const char *name;
+ const unsigned int *supported_cable;
+ const u32 *mutually_exclusive;
+
+ /* Internal data */
+ struct device dev;
+ unsigned int id;
+ struct raw_notifier_head nh_all;
+ struct raw_notifier_head *nh;
+ struct list_head entry;
+ int max_supported;
+ spinlock_t lock;
+ u32 state;
+
+ /* Sysfs related */
+ struct device_type extcon_dev_type;
+ struct extcon_cable *cables;
+ struct attribute_group attr_g_muex;
+ struct attribute **attrs_muex;
+ struct device_attribute *d_attrs_muex;
+ };
+
+Key fields:
+
+- ``name``: Name of the Extcon device
+- ``supported_cable``: Array of supported cable types
+- ``mutually_exclusive``: Array defining mutually exclusive cable types
+ This field is crucial for enforcing hardware constraints. It's an array of
+ 32-bit unsigned integers, where each element represents a set of mutually
+ exclusive cable types. The array should be terminated with a 0.
+
+ For example:
+
+ ::
+
+ static const u32 mutually_exclusive[] = {
+ BIT(0) | BIT(1), /* Cable 0 and 1 are mutually exclusive */
+ BIT(2) | BIT(3) | BIT(4), /* Cables 2, 3, and 4 are mutually exclusive */
+ 0 /* Terminator */
+ };
+
+ In this example, cables 0 and 1 cannot be connected simultaneously, and
+ cables 2, 3, and 4 are also mutually exclusive. This is useful for
+ scenarios like a single port that can either be USB or HDMI, but not both
+ at the same time.
+
+ The Extcon core uses this information to prevent invalid combinations of
+ cable states, ensuring that the reported states are always consistent
+ with the hardware capabilities.
+
+- ``state``: Current state of the device (bitmap of connected cables)
+
+
+extcon_cable
+------------
+
+Represents an individual cable managed by an Extcon device::
+
+ struct extcon_cable {
+ struct extcon_dev *edev;
+ int cable_index;
+ struct attribute_group attr_g;
+ struct device_attribute attr_name;
+ struct device_attribute attr_state;
+ struct attribute *attrs[3];
+ union extcon_property_value usb_propval[EXTCON_PROP_USB_CNT];
+ union extcon_property_value chg_propval[EXTCON_PROP_CHG_CNT];
+ union extcon_property_value jack_propval[EXTCON_PROP_JACK_CNT];
+ union extcon_property_value disp_propval[EXTCON_PROP_DISP_CNT];
+ DECLARE_BITMAP(usb_bits, EXTCON_PROP_USB_CNT);
+ DECLARE_BITMAP(chg_bits, EXTCON_PROP_CHG_CNT);
+ DECLARE_BITMAP(jack_bits, EXTCON_PROP_JACK_CNT);
+ DECLARE_BITMAP(disp_bits, EXTCON_PROP_DISP_CNT);
+ };
+
+Core Functions
+==============
+
+.. kernel-doc:: drivers/extcon/extcon.c
+ :identifiers: extcon_get_state
+
+.. kernel-doc:: drivers/extcon/extcon.c
+ :identifiers: extcon_set_state
+
+.. kernel-doc:: drivers/extcon/extcon.c
+ :identifiers: extcon_set_state_sync
+
+.. kernel-doc:: drivers/extcon/extcon.c
+ :identifiers: extcon_get_property
+
+
+Sysfs Interface
+===============
+
+Extcon devices expose the following sysfs attributes:
+
+- ``name``: Name of the Extcon device
+- ``state``: Current state of all supported cables
+- ``cable.N/name``: Name of the Nth supported cable
+- ``cable.N/state``: State of the Nth supported cable
+
+Usage Example
+-------------
+
+.. code-block:: c
+
+ #include <linux/module.h>
+ #include <linux/platform_device.h>
+ #include <linux/extcon.h>
+
+ struct my_extcon_data {
+ struct extcon_dev *edev;
+ struct device *dev;
+ };
+
+ static const unsigned int my_extcon_cable[] = {
+ EXTCON_USB,
+ EXTCON_USB_HOST,
+ EXTCON_NONE,
+ };
+
+ static int my_extcon_probe(struct platform_device *pdev)
+ {
+ struct my_extcon_data *data;
+ int ret;
+
+ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->dev = &pdev->dev;
+
+ /* Initialize extcon device */
+ data->edev = devm_extcon_dev_allocate(data->dev, my_extcon_cable);
+ if (IS_ERR(data->edev)) {
+ dev_err(data->dev, "Failed to allocate extcon device\n");
+ return PTR_ERR(data->edev);
+ }
+
+ /* Register extcon device */
+ ret = devm_extcon_dev_register(data->dev, data->edev);
+ if (ret < 0) {
+ dev_err(data->dev, "Failed to register extcon device\n");
+ return ret;
+ }
+
+ platform_set_drvdata(pdev, data);
+
+ /* Example: Set initial state */
+ extcon_set_state_sync(data->edev, EXTCON_USB, true);
+
+ dev_info(data->dev, "My extcon driver probed successfully\n");
+ return 0;
+ }
+
+ static int my_extcon_remove(struct platform_device *pdev)
+ {
+ struct my_extcon_data *data = platform_get_drvdata(pdev);
+
+ /* Example: Clear state before removal */
+ extcon_set_state_sync(data->edev, EXTCON_USB, false);
+
+ dev_info(data->dev, "My extcon driver removed\n");
+ return 0;
+ }
+
+ static const struct of_device_id my_extcon_of_match[] = {
+ { .compatible = "my,extcon-device", },
+ { },
+ };
+ MODULE_DEVICE_TABLE(of, my_extcon_of_match);
+
+ static struct platform_driver my_extcon_driver = {
+ .driver = {
+ .name = "my-extcon-driver",
+ .of_match_table = my_extcon_of_match,
+ },
+ .probe = my_extcon_probe,
+ .remove = my_extcon_remove,
+ };
+
+ module_platform_driver(my_extcon_driver);
+
+This example demonstrates:
+---------------------------
+
+- Defining supported cable types (USB and USB Host in this case).
+- Allocating and registering an extcon device.
+- Setting an initial state for a cable (USB connected in this example).
+- Clearing the state when the driver is removed.
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index 7f83e05769b4..16e2c4ec3c01 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -86,6 +86,7 @@ Subsystem-specific APIs
dmaengine/index
dpll
edac
+ extcon
firmware/index
fpga/index
frame-buffer
diff --git a/Documentation/driver-api/pps.rst b/Documentation/driver-api/pps.rst
index 78dded03e5d8..71ad04c82d6c 100644
--- a/Documentation/driver-api/pps.rst
+++ b/Documentation/driver-api/pps.rst
@@ -202,6 +202,46 @@ Sometimes one needs to be able not only to catch PPS signals but to produce
them also. For example, running a distributed simulation, which requires
computers' clock to be synchronized very tightly.
+To do so the class pps-gen has been added. PPS generators can be
+registered in the kernel by defining a struct pps_gen_source_info as
+follows::
+
+ static struct pps_gen_source_info pps_gen_dummy_info = {
+ .name = "dummy",
+ .use_system_clock = true,
+ .get_time = pps_gen_dummy_get_time,
+ .enable = pps_gen_dummy_enable,
+ };
+
+Where the use_system_clock states if the generator uses the system
+clock to generate its pulses, or they are from a peripheral device
+clock. Method get_time() is used to query the time stored into the
+generator clock, while the method enable() is used to enable or
+disable the PPS pulse generation.
+
+Then calling the function pps_gen_register_source() in your
+initialization routine as follows creates a new generator in the
+system::
+
+ pps_gen = pps_gen_register_source(&pps_gen_dummy_info);
+
+Generators SYSFS support
+------------------------
+
+If the SYSFS filesystem is enabled in the kernel it provides a new class::
+
+ $ ls /sys/class/pps-gen/
+ pps-gen0/ pps-gen1/ pps-gen2/
+
+Every directory is the ID of a PPS generator defined in the system and
+inside of it you find several files::
+
+ $ ls -F /sys/class/pps-gen/pps-gen0/
+ dev enable name power/ subsystem@ system time uevent
+
+To enable the PPS signal generation you can use the command below::
+
+ $ echo 1 > /sys/class/pps-gen/pps-gen0/enable
Parallel port generator
------------------------