payloads/tianocore/Kconfig: Extend help for bootsplash file
Add more detail as to why a smaller-than-screen-size image is to be
preferred, in contrast to other payloads' bootsplash images.
Signed-off-by: Felix Friedlander <felix@ffetc.net>
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Change-Id: Ib4c6666bb0e49369fe8fe2ae3dc12c023f668da0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49233
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/payloads/external/tianocore/Kconfig b/payloads/external/tianocore/Kconfig
index 5349f25..a3c9981 100644
--- a/payloads/external/tianocore/Kconfig
+++ b/payloads/external/tianocore/Kconfig
@@ -76,8 +76,18 @@
default "bootsplash.bmp"
help
The path and filename of the file to use as graphical bootsplash
- screen. The file format must be uncompressed BMP, and the file's
- resolution must be less than the native resolution of the display.
+ image. The file must be an uncompressed BMP.
+
+ This image will also be used as the BGRT boot image, which may
+ persist through your OS boot process, and will be displayed
+ vertically centered 38.2% from the top of the display.
+
+ See ACPI spec 6.3, 5.2.22 Boot Graphics Resource Table (BGRT), and
+ Microsoft's documentation on BGRT positioning:
+ Docs/Windows/Windows Drivers/Bring up guide/Boot screen components
+
+ Accordingly, the image used should be no taller/wider than 40% of
+ the display panel's native pixel height/width (or resolution set).
If an absolute path is not given, the path will assumed to be
relative to the coreboot root directory.