+++ /dev/null
-=================
-MEN Chameleon Bus
-=================
-
-.. Table of Contents
- =================
- 1 Introduction
- 1.1 Scope of this Document
- 1.2 Limitations of the current implementation
- 2 Architecture
- 2.1 MEN Chameleon Bus
- 2.2 Carrier Devices
- 2.3 Parser
- 3 Resource handling
- 3.1 Memory Resources
- 3.2 IRQs
- 4 Writing an MCB driver
- 4.1 The driver structure
- 4.2 Probing and attaching
- 4.3 Initializing the driver
-
-
-Introduction
-============
-
-This document describes the architecture and implementation of the MEN
-Chameleon Bus (called MCB throughout this document).
-
-Scope of this Document
-----------------------
-
-This document is intended to be a short overview of the current
-implementation and does by no means describe the complete possibilities of MCB
-based devices.
-
-Limitations of the current implementation
------------------------------------------
-
-The current implementation is limited to PCI and PCIe based carrier devices
-that only use a single memory resource and share the PCI legacy IRQ. Not
-implemented are:
-
-- Multi-resource MCB devices like the VME Controller or M-Module carrier.
-- MCB devices that need another MCB device, like SRAM for a DMA Controller's
- buffer descriptors or a video controller's video memory.
-- A per-carrier IRQ domain for carrier devices that have one (or more) IRQs
- per MCB device like PCIe based carriers with MSI or MSI-X support.
-
-Architecture
-============
-
-MCB is divided into 3 functional blocks:
-
-- The MEN Chameleon Bus itself,
-- drivers for MCB Carrier Devices and
-- the parser for the Chameleon table.
-
-MEN Chameleon Bus
------------------
-
-The MEN Chameleon Bus is an artificial bus system that attaches to a so
-called Chameleon FPGA device found on some hardware produced my MEN Mikro
-Elektronik GmbH. These devices are multi-function devices implemented in a
-single FPGA and usually attached via some sort of PCI or PCIe link. Each
-FPGA contains a header section describing the content of the FPGA. The
-header lists the device id, PCI BAR, offset from the beginning of the PCI
-BAR, size in the FPGA, interrupt number and some other properties currently
-not handled by the MCB implementation.
-
-Carrier Devices
----------------
-
-A carrier device is just an abstraction for the real world physical bus the
-Chameleon FPGA is attached to. Some IP Core drivers may need to interact with
-properties of the carrier device (like querying the IRQ number of a PCI
-device). To provide abstraction from the real hardware bus, an MCB carrier
-device provides callback methods to translate the driver's MCB function calls
-to hardware related function calls. For example a carrier device may
-implement the get_irq() method which can be translated into a hardware bus
-query for the IRQ number the device should use.
-
-Parser
-------
-
-The parser reads the first 512 bytes of a Chameleon device and parses the
-Chameleon table. Currently the parser only supports the Chameleon v2 variant
-of the Chameleon table but can easily be adopted to support an older or
-possible future variant. While parsing the table's entries new MCB devices
-are allocated and their resources are assigned according to the resource
-assignment in the Chameleon table. After resource assignment is finished, the
-MCB devices are registered at the MCB and thus at the driver core of the
-Linux kernel.
-
-Resource handling
-=================
-
-The current implementation assigns exactly one memory and one IRQ resource
-per MCB device. But this is likely going to change in the future.
-
-Memory Resources
-----------------
-
-Each MCB device has exactly one memory resource, which can be requested from
-the MCB bus. This memory resource is the physical address of the MCB device
-inside the carrier and is intended to be passed to ioremap() and friends. It
-is already requested from the kernel by calling request_mem_region().
-
-IRQs
-----
-
-Each MCB device has exactly one IRQ resource, which can be requested from the
-MCB bus. If a carrier device driver implements the ->get_irq() callback
-method, the IRQ number assigned by the carrier device will be returned,
-otherwise the IRQ number inside the Chameleon table will be returned. This
-number is suitable to be passed to request_irq().
-
-Writing an MCB driver
-=====================
-
-The driver structure
---------------------
-
-Each MCB driver has a structure to identify the device driver as well as
-device ids which identify the IP Core inside the FPGA. The driver structure
-also contains callback methods which get executed on driver probe and
-removal from the system::
-
- static const struct mcb_device_id foo_ids[] = {
- { .device = 0x123 },
- { }
- };
- MODULE_DEVICE_TABLE(mcb, foo_ids);
-
- static struct mcb_driver foo_driver = {
- driver = {
- .name = "foo-bar",
- .owner = THIS_MODULE,
- },
- .probe = foo_probe,
- .remove = foo_remove,
- .id_table = foo_ids,
- };
-
-Probing and attaching
----------------------
-
-When a driver is loaded and the MCB devices it services are found, the MCB
-core will call the driver's probe callback method. When the driver is removed
-from the system, the MCB core will call the driver's remove callback method::
-
- static init foo_probe(struct mcb_device *mdev, const struct mcb_device_id *id);
- static void foo_remove(struct mcb_device *mdev);
-
-Initializing the driver
------------------------
-
-When the kernel is booted or your foo driver module is inserted, you have to
-perform driver initialization. Usually it is enough to register your driver
-module at the MCB core::
-
- static int __init foo_init(void)
- {
- return mcb_register_driver(&foo_driver);
- }
- module_init(foo_init);
-
- static void __exit foo_exit(void)
- {
- mcb_unregister_driver(&foo_driver);
- }
- module_exit(foo_exit);
-
-The module_mcb_driver() macro can be used to reduce the above code::
-
- module_mcb_driver(foo_driver);
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