GPIO

Overview

In the Hardware Driver Foundation (HDF) framework, the general-purpose input/output (GPIO) module uses the service-free mode for API adaptation. The service-free mode applies to the devices that do not provide user-mode APIs or the OS system that does not distinguish the user mode and the kernel mode. In the service-free mode, DevHandle (a void pointer) directly points to the kernel-mode address of the device object.

Figure 1 Service-free mode

Available APIs

GpioMethod

struct GpioMethod {
  int32_t (*request)(struct GpioCntlr *cntlr, uint16_t local);// Reserved
  int32_t (*release)(struct GpioCntlr *cntlr, uint16_t local);// Reserved
  int32_t (*write)(struct GpioCntlr *cntlr, uint16_t local, uint16_t val);
  int32_t (*read)(struct GpioCntlr *cntlr, uint16_t local, uint16_t *val);
  int32_t (*setDir)(struct GpioCntlr *cntlr, uint16_t local, uint16_t dir);
  int32_t (*getDir)(struct GpioCntlr *cntlr, uint16_t local, uint16_t *dir);
  int32_t (*toIrq)(struct GpioCntlr *cntlr, uint16_t local, uint16_t *irq);// Reserved
  int32_t (*setIrq)(struct GpioCntlr *cntlr, uint16_t local, uint16_t mode, GpioIrqFunc func, void *arg);
  int32_t (*unsetIrq)(struct GpioCntlr *cntlr, uint16_t local);
  int32_t (*enableIrq)(struct GpioCntlr *cntlr, uint16_t local);
  int32_t (*disableIrq)(struct GpioCntlr *cntlr, uint16_t local);
}

Table 1 Callbacks for the members in the GpioMethod structure

Callback	Input Parameter	Output Parameter	Return Value	Description
write	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type. val: input level value, which is of the uint16_t type.	–	HDF_STATUS	Writes the level of a GPIO pin.
read	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type.	val: pointer to the output level value, which is of the uint16_t type.	HDF_STATUS	Reads the level of a GPIO pin.
setDir	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type. dir: input pin direction, which is of the uint16_t type.	–	HDF_STATUS	Sets the input or output direction for a GPIO pin.
getDir	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type.	dir: pointer to the output pin direction, which is of the uint16_t type.	HDF_STATUS	Obtains the input or output direction of a GPIO pin.
setIrq	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type. mode: triggering mode, which can be edge or level. The value is of the uint16_t type. func: function pointer to the interrupt service handler. arg: void pointer to the input parameters of the interrupt service handler.	–	HDF_STATUS	Sets an interrupt request (IRQ) for a GPIO pin.
unsetIrq	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type.	–	HDF_STATUS	Cancels the GPIO interrupt settings.
enableIrq	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type.	–	HDF_STATUS	Enables an interrupt for a GPIO pin.
disableIrq	cntlr: structure pointer to the GPIO controller at the core layer. local: GPIO port number, which is of the uint16_t type.	–	HDF_STATUS	Disables an interrupt for a GPIO pin.

How to Develop

The GPIO controller manages all pins by group. The related parameters are described in the attribute file. Instantiating the driver entry and API functions is the core for the vendor driver to access the HDF.

The GPIO module adaptation involves the following steps:

Instantiate the driver entry.
- Instantiate the HdfDriverEntry structure.
- Call HDF_INIT to register the HdfDriverEntry instance with the HDF framework.
Configure attribute files.
- Add the deviceNode information to the device_info.hcs file.
- (Optional) Add the gpio_config.hcs file.
Instantiate the GPIO controller object.
- Initialize GpioCntlr.
- Instantiate GpioMethod in the GpioCntlr object.
  
  NOTE: For details, see Available APIs.
Debug the driver.
- (Optional) For new drivers, verify the basic functions, such as the GPIO control status and response to interrupts.

Development Example

The following uses gpio_hi35xx.c as an example to present the contents that need to be provided by the vendor to implement device functions.

Instantiate the driver entry. The driver entry must be a global variable of the HdfDriverEntry type (defined in hdf_device_desc.h), and the value of moduleName must be the same as that in device_info.hcs. In the HDF framework, the start address of each HdfDriverEntry object of all loaded drivers is collected to form a segment address space similar to an array for the upper layer to invoke.

Generally, HDF calls the Bind function and then the Init function to load a driver. If Init fails to be called, HDF calls Release to release driver resources and exits.

GPIO driver entry reference

struct HdfDriverEntry g_gpioDriverEntry = {
  .moduleVersion = 1,
  .Bind = Pl061GpioBind, // Bind does not need to be implemented for GPIO. In this example, the implementation is empty. Vendors can add related operations as required.
  .Init = Pl061GpioInit,            // See the Init function.
   .Release = Pl061GpioRelease,      // See the Release function.
  .moduleName = "hisi_pl061_driver",// (Mandatory) The value must be the same as that of moduleName in the .hcs file.
};
// Call HDF_INIT to register the driver entry with the HDF framework.
HDF_INIT(g_gpioDriverEntry);

Add the deviceNode information to the device_info.hcs file and configure the device attributes in the gpio_config.hcs file. The deviceNode information is related to registration of the driver entry. The device attribute values are closely related to the default values or value ranges of the GpioCntlr members at the core layer.

In this example, there is only one GPIO controller. If there are multiple GPIO controllers, you need to add the deviceNode information to the device_info file and add the corresponding device attributes to the gpio_config file.

device_info.hcs configuration reference

root {
device_info {
    platform :: host {
    hostName = "platform_host";
    priority = 50;
    device_gpio :: device {
        device0 :: deviceNode {
 policy = 0; // The value 0 indicates that no service needs to be published.
 priority = 10; // Driver startup priority
 permission = 0644; // Permission to create device nodes for the driver
        moduleName = "hisi_pl061_driver";         // (Mandatory) Driver name, which must be the same as the moduleName in the driver entry.
          deviceMatchAttr = "hisilicon_hi35xx_pl061";// (Mandatory) Used to configure the private data of the controller. The value must be the same as the controller information in gpio_config.hcs.
                                                    // The controller information must be consistent. Other controller information is also contained in the file.
        }
    }
    }
}
}

gpio_config.hcs configuration reference

root {
platform {
    gpio_config {
    controller_0x120d0000 {
        match_attr = "hisilicon_hi35xx_pl061"; // (Mandatory) The value must be the same as that of deviceMatchAttr in device_info.hcs.
        groupNum = 12; // (Mandatory) GPIO group index
        bitNum = 8; // (Mandatory) Number of GPIO pins in each group
        regBase = 0x120d0000;// (Mandatory) Physical base address
        regStep = 0x1000; // (Mandatory) Register offset step
        irqStart = 48; // (Mandatory) Start an IRQ.
        irqShare = 0; // (Mandatory) Share the IRQ.
    }
    }
}
}

Initialize the GpioCntlr object at the core layer, including initializing the vendor custom structure (transferring parameters and data), instantiating GpioMethod (used to call underlying functions of the driver) in GpioCntlr, and implementing the HdfDriverEntry member functions (Bind, Init, and Release).

Custom structure reference

To the driver, the custom structure carries parameters and data. The values in the gpio_config.hcs file are read by HDF, and the structure members are initialized through DeviceResourceIface. Some important values, such as the index and the number of pins, are also passed to the GpioCntlr object at the core layer.

struct Pl061GpioCntlr {
  struct GpioCntlr cntlr;// (Mandatory) Control object of the core layer. For details about the member definitions, see the following description.
    volatile unsigned char  *regBase; // (Mandatory) Base address of the register
  uint32_t phyBase; // (Mandatory) Physical base address
  uint32_t regStep;  // (Mandatory) Register offset step
  uint32_t irqStart; // (Mandatory) Start an IRQ.
  uint16_t groupNum; // (Mandatory) GPIO port number
  uint16_t bitNum; // (Mandatory) GPIO port number
  uint8_t irqShare; // (Mandatory) Share the IRQ.
  struct Pl061GpioGroup *groups; // (Optional) Set based on the vendor's requirements.
};
struct Pl061GpioGroup {// Register address, interrupt number, interrupt function, and lock
  volatile unsigned char *regBase;
  unsigned int index;
  unsigned int irq;
  OsalIRQHandle irqFunc;
  OsalSpinlock lock;
};

// GpioCntlr is the controller structure at the core layer. Its members are assigned with values by using the Init function.
struct GpioCntlr {
  struct IDeviceIoService service;
  struct HdfDeviceObject *device;
  struct GpioMethod *ops;
  struct DListHead list;
  OsalSpinlock spin;
  uint16_t start;
  uint16_t count;
  struct GpioInfo *ginfos;
  void *priv;
};

Instantiate the callback function structure GpioMethod in GpioCntlr. Other members are initialized by using the Init function.

// The members of the GpioMethod structure are all callbacks. Vendors need to implement the corresponding functions according to [Table 1](#table151341544111).
static struct GpioMethod g_method = {
    .request = NULL,
    .release = NULL,
    .write = Pl061GpioWrite, // Write pin settings.
    .read = Pl061GpioRead, // Read pin settings.
    .setDir = Pl061GpioSetDir, // Set the pin direction.
    .getDir = Pl061GpioGetDir, // Obtain the pin direction.
    .toIrq = NULL,
    .setIrq = Pl061GpioSetIrq, // Set an interrupt for the pin. If this capability is not available, skip it.
    .unsetIrq = Pl061GpioUnsetIrq, // Cancel the interrupt settings for the pin. If this capability is not available, skip it.
    .enableIrq = Pl061GpioEnableIrq,  // Enable an interrupt for the pin. If this capability is not available, skip it.
    .disableIrq = Pl061GpioDisableIrq,// Disable the interrupt for the pin. If this capability is not available, skip it. 
};

Init function

Input parameters:

HdfDeviceObject, an interface parameter exposed by the driver, contains the .hcs configuration file information.

Return values:

HDF_STATUS (The following table lists some status. For details about other status, see HDF_STATUS in the //drivers/framework/include/utils/hdf_base.h file.)

Table 2 Init function description

Status (Value)	Description
HDF_ERR_INVALID_OBJECT	Invalid controller object
HDF_ERR_MALLOC_FAIL	Failed to allocate memory
HDF_ERR_INVALID_PARAM	Invalid parameter
HDF_ERR_IO	I/O error
HDF_SUCCESS	Initialization successful
HDF_FAILURE	Initialization failed

Function description:

Initializes the custom structure object and GpioCntlr, calls the GpioCntlrAdd function at the core layer, and connects to the VFS (optional).

static int32_t Pl061GpioInit(struct HdfDeviceObject *device)
{
  ...
 struct Pl061GpioCntlr *pl061 = &g_pl061;// Use static global variables to complete initialization.
                                          //static struct Pl061GpioCntlr g_pl061 = {
                                          //    .groups = NULL,
                                          //    .groupNum = PL061_GROUP_MAX,
                                          //    .bitNum = PL061_BIT_MAX,
                                          //};
   ret = Pl061GpioReadDrs(pl061, device->property);// Use the attribute values read from the gpio_config.HCS file to initialize the members of the custom structure object.
  ...
  pl061->regBase = OsalIoRemap(pl061->phyBase, pl061->groupNum * pl061->regStep);// Address mapping
  ...
  ret = Pl061GpioInitCntlrMem(pl061); // Apply for memory.
  ...
  pl061->cntlr.count = pl061->groupNum x pl061->bitNum;// (Mandatory) Calculate the number of pins.
  pl061->cntlr.priv = (void *)device->property; // (Mandatory) Store device attributes.
  pl061->cntlr.ops = &g_method;      // (Mandatory) Connect to the GpioMethod instance.
   pl061->cntlr.device = device;  // (Mandatory) Enable conversion between HdfDeviceObject and GpioCntlr.
ret = GpioCntlrAdd(&pl061->cntlr);    // (Mandatory) Call this function to set the structure of the core layer. The driver accesses the platform core layer only after a success signal is returned.
  ...
  Pl061GpioDebugCntlr(pl061);
  #ifdef PL061_GPIO_USER_SUPPORT // (Optional) Access the user-level virtual file system if supported.
  if (GpioAddVfs(pl061->bitNum) != HDF_SUCCESS) {
      HDF_LOGE("%s: add vfs fail!", __func__);
  }
  #endif
  ...
}

Release function

Input parameters:

HdfDeviceObject, an interface parameter exposed by the driver, contains the .hcs configuration file information.

Return values:

–

Function description:

Releases the memory and deletes the controller. This function assigns a value to the Release API in the driver entry structure. When the HDF framework fails to call the Init function to initialize the driver, the Release function can be called to release driver resources. All forced conversion operations for obtaining the corresponding object can be successful only when the Init function has the corresponding value assignment operations.

    static void Pl061GpioRelease(struct HdfDeviceObject *device)
    {
       struct GpioCntlr *cntlr = NULL;
       struct Pl061GpioCntlr *pl061 = NULL;
       ...
       cntlr = GpioCntlrFromDevice(device);// (Mandatory) Obtain the control object of the core layer through forced conversion.
                                           //return (device == NULL) ? NULL : (struct GpioCntlr *)device->service;
       ...
       #ifdef PL061_GPIO_USER_SUPPORT
       GpioRemoveVfs();// Perform operations reverse to GpioAddVfs in Init.
       #endif
       GpioCntlrRemove(cntlr);             // (Mandatory) Remove the device information and services from the core layer.
       pl061 = ToPl061GpioCntlr(cntlr);    //return (struct Pl061GpioCntlr *)cntlr;
       Pl061GpioRleaseCntlrMem(pl061);     // (Mandatory) Release the lock and memory.
       OsalIoUnmap((void *)pl061->regBase);// (Mandatory) Remove the address mapping.
       pl061->regBase = NULL;
    }
    ```