Platform bus

    platform The development steps of bus driver are ：

    1、 equipment

    The structure to be implemented is ：platform_device .

    1） initialization resource Structural variable

    2） initialization platform_device Structural variable

    3） Register the device with the system ：platform_device_register.( Registration means cancellation ,platform_device_unregister, It is usually called when unloading the driver )

    Three steps above , It must be done before the device driver is loaded , The perform platform_driver_register（） Before , The reason is that driver registration needs to match all registered device names in the kernel .platform_driver_register（） Add device In the end, it's called by the kernel device_add function .Platform_device_add and device_add The main difference is one more step insert_resource（p, r）, the platform resources （resource） Add to the kernel , Managed by the kernel .

/linux/platform_device.h

struct platform_device {
	const char	*name;// Drive to match , load device It will be in sys/bus/platfrom/devices The name of the path is name Node file 
	int		id;  // equipment id, Give the same name The equipment is numbered , If there is only one device , Fill in -1 that will do 
	bool		id_auto;
	struct device	dev;// General properties of equipment 
	u64		platform_dma_mask;
	struct device_dma_parameters dma_parms;
	u32		num_resources;   // The amount of resources 
	struct resource	*resource;   //device Hardware resources in , Register address , Interrupt number , Clock and so on 

	const struct platform_device_id	*id_entry;
	char *driver_override; /* Driver name to force a match */

	/* MFD cell pointer */
	struct mfd_cell *mfd_cell;

	/* arch specific additions */
	struct pdev_archdata	archdata;
};

linux/ioport.h

struct resource {
    resource_size_t start;
    resource_size_t end;
    const char      *name;
    unsigned long   flags;
    struct resource *parent, *sibling, *child;
};

flags Bits can represent the type of resource , As follows ：
#define IORESOURCE_BITS		0x000000ff	/* Bus-specific bits */

#define IORESOURCE_TYPE_BITS	0x00001f00	/* Resource type */
#define IORESOURCE_IO		0x00000100	/* PCI/ISA I/O ports */
#define IORESOURCE_MEM		0x00000200  /*  Represents a piece of physical memory  */
#define IORESOURCE_REG		0x00000300	/* Register offsets */
#define IORESOURCE_IRQ		0x00000400  /*  Interrupt number  */
#define IORESOURCE_DMA		0x00000800
#define IORESOURCE_BUS		0x00001000  /*  Bus , Such as IIC Bus ,SPI Bus etc.  */

   2、 drive

initialization platform_driver Structural variable , contain prober Functions, etc

call platform_driver_register Register the driver with the platform bus

Be careful ：

1、 Load the driver first and load the device first , There is no order

2、platform_driver ->id_table->name and platform_driver->driver->name Are used to match the equipment , And platform_driver ->id_table->name Priority of . That is, when there are both , But inconsistent , With platform_driver ->id_table->name Subject to .

///include/linux/platform_device.h

struct platform_driver {
	int (*probe)(struct platform_device *);  //device and driver If the match is successful, this function will be executed 
	int (*remove)(struct platform_device *);  //device and driver Any one rm This function will be executed when 
	void (*shutdown)(struct platform_device *);  //device received shutdown Command to execute this function 
	int (*suspend)(struct platform_device *, pm_message_t state); //device After receiving the sleep command, execute this function 
	int (*resume)(struct platform_device *);  //device After receiving the wake-up command, execute this function 
	struct device_driver driver;  //
	const struct platform_device_id *id_table; // There is also one in this structure Name member , Also used matching equipment , This priority is higher than device Medium name higher 
	bool prevent_deferred_probe;
};

///include/linux/device/driver.h
struct device_driver {
	const char		*name; // The name used in matching 
	struct bus_type		*bus;

	struct module		*owner;   // It's usually THIS_MODULE
	const char		*mod_name;	/* used for built-in modules */

	bool suppress_bind_attrs;	/* disables bind/unbind via sysfs */
	enum probe_type probe_type;

	const struct of_device_id	*of_match_table;   // Combined with device tree , Set the matching table with the device tree 
	const struct acpi_device_id	*acpi_match_table;

	int (*probe) (struct device *dev);
	void (*sync_state)(struct device *dev);
	int (*remove) (struct device *dev);
	void (*shutdown) (struct device *dev);
	int (*suspend) (struct device *dev, pm_message_t state);
	int (*resume) (struct device *dev);
	const struct attribute_group **groups;
	const struct attribute_group **dev_groups;

	const struct dev_pm_ops *pm;
	void (*coredump) (struct device *dev);

	struct driver_private *p;
};

struct platform_device_id {
	char name[PLATFORM_NAME_SIZE]; // It is also used to match the equipment , This has a high priority 
	kernel_ulong_t driver_data;
};

probe Function writing ideas ：

from device.c Get hardware resources in

Method 1 ：int (*probe)(struct platform_device *) The formal parameter in the function points to platform_device Structure , Directly access the formal parameter ( Not recommended )

Method 2 ： Use API Function access ,struct resource *platform_get_resource(struct platform_device *dev,unsigned int type, unsigned int num),type It's the type of resource , and flags Corresponding ,num Said is similar Number of resources .

Register driver , perfect file_operation Structure , And generate device nodes

ref：

platform_device.h - include/linux/platform_device.h - Linux source code (v5.16.9) - Bootlin

ioport.h - include/linux/ioport.h - Linux source code (v5.16.9) - Bootlin