Re: Display Architecture and Bring Up in UEFI

[Laszlo Ersek <lersek@redhat.com>]

On 11/23/18 07:27, prabin ca wrote:
> Hi Team,
> 
> I’m new to UEFI and display interface in UEFI. I would like to have deep dive into how display is working in UEFI (display architecture) and how display is have been bring up (porting of display panel in a any platform in general ).
> 
> Please help me with sample codes and necessary documents. I would like to get knowledge about display bring up and display architecture in UEFI

The driver writers' guide and the UEFI spec have relevant chapters on
this. I think it's best to start reading the former, at "23 Graphics
Driver Design Guidelines"; that part will give you the pointers to the
rest as well.

https://github.com/tianocore/tianocore.github.io/wiki/UEFI-Driver-Writer%27s-Guide


For a (hopefully educational) example, I refer you to
OvmfPkg/VirtioGpuDxe. In the series that first added this driver to
edk2, I managed to construct the driver in stages such that each stage
would build and even function, at the level expected from that stage. In
particular, commit a2a4fa66701d ("OvmfPkg/VirtioGpuDxe: introduce with
Component Name 2 and Driver Binding", 2016-09-01) could prove helpful,
as it adds the skeleton of the driver, mostly without VirtIo GPU specifics.


In addition, you might want to look into the generic

  MdeModulePkg/Universal/Console/GraphicsOutputDxe

driver. A platform may be able to incorporate that driver without any
changes, and control it by first producing the two HOBs in the PEI phase
that the driver consumes:

  MdePkg/Include/Guid/GraphicsInfoHob.h

(... Interestingly, due to the fact that this header file is under
MdePkg and not MdeModulePkg, I've just learned, from the related commit
messages, that the PEI phase has standardized graphics support,
described in the PI spec. From the following two commit messages:

- 697c6cf32693 ("MdePkg: Add PI 1.4 Graphics HOB and PPI header files",
2015-04-28)

- 2af538fbf667 ("MdeModulePkg: Add GraphicsOutputDxe driver.", 2016-10-12)

it appears that enabling graphics support in the PEI phase could be a
*requirement* for using GraphicsOutputDxe in the DXE phase. That might
or might not match your use case, so perhaps it will prevent you from
using GraphicsOutputDxe. I'm not sure.)

Thanks
Laszlo