1. Introduction
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---------------
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**MvEeprom** driver creates MARVELL_EEPROM_PROTOCOL, which
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+is used for managing eeprom.
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2. MvEeprom driver design
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-------------------------
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Every I2C device driver should implement EFI_DRIVER_BINDING_PROTOCOL and
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consume EFI_I2C_IO_PROTOCOL for transactions on I2C bus. MvEeprom driver
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additionally implements MARVELL_EEPROM_PROTOCOL.
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2.1 EFI_DRIVER_BINDING_PROTOCOL
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-------------------------------
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Driver Binding protocol is extensively covered in UEFI documentation, as
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it is not specific to I2C stack. The only difference is that Supported()
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function should check if EFI_I2C_IO_PROTOCOL provides valid EFI_GUID and
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DeviceIndex values.
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Excerpt from MvEepromSupported():
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Status = gBS->OpenProtocol (
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ControllerHandle,
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&gEfiI2cIoProtocolGuid,
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(VOID **) &TmpI2cIo,
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gImageHandle,
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ControllerHandle,
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EFI_OPEN_PROTOCOL_BY_DRIVER
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);
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if (EFI_ERROR(Status)) {
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return EFI_UNSUPPORTED;
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}
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/* get EEPROM devices' addresses from PCD */
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EepromAddresses = PcdGetPtr (PcdEepromI2cAddresses);
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if (EepromAddresses == 0) {
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Status = EFI_UNSUPPORTED;
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goto out;
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}
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Status = EFI_UNSUPPORTED;
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for (i = 0; EepromAddresses[i] != '\0'; i++) {
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/* I2C guid must fit and valid DeviceIndex must be provided */
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if (CompareGuid(TmpI2cIo->DeviceGuid, &I2cGuid) &&
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TmpI2cIo->DeviceIndex == EepromAddresses[i]) {
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DEBUG((DEBUG_INFO, "A8kEepromSupported: attached to EEPROM device\n"));
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Status = EFI_SUCCESS;
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break;
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}
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}
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2.2 EFI_I2C_IO_PROTOCOL
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-----------------------
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This protocol is provided by generic I2C stack. Multiple drivers can use IO
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protocol at once, as queueing is implemented.
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QueueRequest is a routine that queues an I2C transaction to the I2C
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controller for execution on the I2C bus.
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2.3 MARVELL_EEPROM_PROTOCOL
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-----------------------
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typedef struct _MARVELL_EEPROM_PROTOCOL MARVELL_EEPROM_PROTOCOL;
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#define EEPROM_READ 0x1
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#define EEPROM_WRITE 0x0
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typedef
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EFI_STATUS
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(EFIAPI *EFI_EEPROM_TRANSFER) (
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IN CONST MARVELL_EEPROM_PROTOCOL *This,
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IN UINT16 Address,
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IN UINT32 Length,
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IN UINT8 *Buffer,
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IN UINT8 Operation
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);
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struct _MARVELL_EEPROM_PROTOCOL {
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EFI_EEPROM_TRANSFER Transfer;
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UINT8 Identifier;
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};
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3. Adding new I2C slave device drivers
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--------------------------------------
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In order to support I2C slave device other than EEPROM, new driver should
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be created. Required steps follow.
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1. Create driver directory (Platform/Marvell/Drivers/I2c/Devices/...).
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2. Create stubs of .inf and .c files (MvEeprom files are a reference),
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include .inf file in platform .dsc and .fdf files.
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3. Implement EFI_DRIVER_BINDING_PROTOCOL - Start(), Stop(), Supported()
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functions' implementation is a must. EFI_DRIVER_BINDING_PROTOCOL
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should be installed at driver's entry point.
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4. Add I2C address of device to PcdI2cSlaveAddresses in .dsc file.
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5. Test available EFI_I2C_IO_PROTOCOLs in Supported() - find instance
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with valid GUID and DeviceIndex (I2C slave address).
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6. Open EFI_I2C_IO_PROTOCOL for usage in Start(). After that, QueueRequest
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function should be available.
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7. Implement core functionality of driver (using QueueRequest to access I2C).
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8. (not mandatory) Produce/consume additional protocols.
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