Smbus Driver Initialization11/8/2020
This post will be the 1st in a collection describing the adjustments in the System Initialization (PI) 1.3 standards.The PI specification is usually like the unheralded young brother of the UEFI standards.
Smbus Initialization Drivers And ProgramsFrom the really starting it was a requirement that PI implementations become able to create UEFI, but it had been furthermore a requirement that UEFI drivers and programs and Operating-system loaders not really rely on the PI standards.If something has been really needed for UEFI, it would obtain advertised (yes, that is the phrase utilized) from the PI specification. Why Because there have been (and are usually) implementations of UEFI which are not built on top of the tianocoré.org EDK1 ór EDK2 implementations ór even Intels old Platfrom Innovation Structure. It has been called the Platform Initialization (PI) standards because, in the UEFI 2.0 standards (and the earlier EFI 1.x specs), one of the engine block blueprints of UEFI acquired a large blank box labeled (you guessed it): Platform Initialization UEFI actually deals with booting. Yes, yes, theres a lot of additional things around user user interface (HII) and protection and networking, but it is certainly all about obtaining the right boot device and loading the Operating-system. If you are not really a boot gadget (or a video device or a key pad), you dont actually get a great deal of respect in UEFI. ![]() I2C didnt get a great deal of respect either in the UEFI globe, ever since Intel started advertising the smarter, enumerable edition, called SMBus. But it transforms out that, as a simple, low-cost, reduced speed, low-power tour bus, it functions well for controlling on-the-motherboard devices, like touch panels, MEMS receptors, small EEPROMs and additional devices with relatively low information rates. Within PI, SMBus experienced from just have got a sponsor controller protocol, but it was never extended out to a genuine driver stack like, state, USB or PCI. Sad. If you desire to notice how its actually done, appear at my presentation from the UEFI plugfest back again in 2011. But back to I2C. The pursuing diagram displays the common driver stack. It appears very related to the typical UEFI drivers bunch, with a sponsor controller process and an IO process. But after that it will get a bit unusual: what are usually the enumerate, shuttle bus configuration management and grasp protocol. You cant stick at some sign up and discover that a device is existing. So, instead, the I actually2C driver stack depends on a system drivers to produce the I2C Enumerate process to return back a list of products actually present on the platform. Second, since it is definitely possible for the I actually2C shuttle bus to end up being one of several different adjustments, it is certainly important that the coach be placed in the correct construction before speaking to a specific device. ![]() That control is offered by the I2C Tour bus Configuration Management protocol. ![]() In common, the gadget drivers use the Host protocol to queue an I2M transaction. The Professional protocol is usually utilized when it will be required to proceed out of order and send an I actually2C control. This happens, for instance, when the platform driver desires to send an order to a multiplexer or tour bus clock device before an I2D command is certainly delivered to a device. With the I actually2C methods, the PI 1.3 specification gives a car owner stack so that you can create a device car owner for an I2C device that functions on any platform. In PEI, only the Get good at capabilities are obtainable through the I2C Professional PPI.
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