Linux Kernel SPI bus driver analysis (2)

SPI driver writing

 

In short, the writing of the SPI driver is divided:

1. Build and register the spi_device

Add in the Board FileSpi_board_info, which is called in the init function of the Board FileSpi_register_board_info (cloud_spi_devs, array_size (cloud_spi_devs ));

Spi_register_board_info(Cloud_spi_devs, array_size (cloud_spi_devs); // register spi_board_info. This code registers spi_board_info to the linked list board_list. Spi_device encapsulates a spi_master struct. In fact, the registration of spi_master will call scan_boardinfo to scan board_list and find the SPI device attached to it after spi_register_board_info, then create and register the spi_device.

 

2.Build and register spi_driver

(1)

Static struct spi_driver m25p80_driver = {

 

. Driver = {

. Name = "m25p80 ",

. Bus = & spi_bus_type,

. Owner = this_module,

},

. Probe = m25p_probe,

. Remove =__ devexit_p (m25p_remove ),

};

(2)// Register spi_driver

 

Spi_register_driver (& m25p80_driver );Spi_deviceCall probe later

 

(3) Implement the probe operation:

 

 

 

 

 

Spi_transfer (which integrates data Buf space addresses and other information)

 

Construction of spi_message (a collection of spi_transfer;

 

Spi_message_init (initialize spi_message)

 

Spi_message_add_tail (Add the new spi_transfer to the end of the spi_message Queue)

 

 

Spi_sync function call (call spi_master to send spi_message)

 

For example:

 

Struct spi_transfer ST = {

 

 

 

.........

 

 

};

 

// Fill in spi_transfer

 

 

Struct spi_message Meg;

 

 

// Define message

 

 

Spi_init_message (& MEG );

 

// Initialize Meg

 

 

Spi_message_add_tail (& St, & MEG );

 

 

// Put the st at the end of the message queue

 

 

Spi_sync (spi_device, & MEG );

 

 

// Associate message with spi_device and send Meg