diff options
Diffstat (limited to 'Lessons/Lesson_25')
| -rw-r--r-- | Lessons/Lesson_25/README.md | 19 | ||||
| -rw-r--r-- | Lessons/Lesson_25/UefiLessonsPkg/PCDLesson/PCDLesson.c | 10 |
2 files changed, 26 insertions, 3 deletions
diff --git a/Lessons/Lesson_25/README.md b/Lessons/Lesson_25/README.md index 15b0b85..ccbcc90 100644 --- a/Lessons/Lesson_25/README.md +++ b/Lessons/Lesson_25/README.md @@ -144,6 +144,25 @@ PcdDynamicInt32=0xCAFECAFE PcdDynamicInt32=0xBEEFBEEF ``` +As we don't always use our application as a part of Ovmf package it would be better to guard the `PcdDynamicInt32` access for cases when local tokan is unassigned. + +We can do it with a help of a `PcdToken` macro: +``` +#define PcdToken(TokenName) _PCD_TOKEN_##TokenName +``` + +Code usage as simple as this: +``` +if (PcdToken(PcdDynamicInt32)) { + Print(L"PcdDynamicInt32=0x%x\n", PcdGet32(PcdDynamicInt32)); + PcdSet32S(PcdDynamicInt32, 0xBEEFBEEF); + Print(L"PcdDynamicInt32=0x%x\n", PcdGet32(PcdDynamicInt32)); +} else { + Print(L"PcdDynamicInt32 token is unassigned\n"); +} +``` +At least now if you accidently copy `Build/UefiLessonsPkg/RELEASE_GCC5/X64/PCDLesson.efi` instead of `Build/OvmfX64/RELEASE_GCC5/X64/PCDLesson.efi` the application won't break the OVMF. + # Dynamic Ex PCD Suppose we already have the necessary PCD in the PCD Database. And we want to access it via application from the UEFI Shell. diff --git a/Lessons/Lesson_25/UefiLessonsPkg/PCDLesson/PCDLesson.c b/Lessons/Lesson_25/UefiLessonsPkg/PCDLesson/PCDLesson.c index 904404f..a3ecfeb 100644 --- a/Lessons/Lesson_25/UefiLessonsPkg/PCDLesson/PCDLesson.c +++ b/Lessons/Lesson_25/UefiLessonsPkg/PCDLesson/PCDLesson.c @@ -57,9 +57,13 @@ UefiMain ( Print(L"Status=%r\n", Status); Print(L"PcdPatchableInt32=%d\n", PatchPcdGet32(PcdPatchableInt32)); //------- - Print(L"PcdDynamicInt32=0x%x\n", PcdGet32(PcdDynamicInt32)); - PcdSet32S(PcdDynamicInt32, 0xBEEFBEEF); - Print(L"PcdDynamicInt32=0x%x\n", PcdGet32(PcdDynamicInt32)); + if (PcdToken(PcdDynamicInt32)) { + Print(L"PcdDynamicInt32=0x%x\n", PcdGet32(PcdDynamicInt32)); + PcdSet32S(PcdDynamicInt32, 0xBEEFBEEF); + Print(L"PcdDynamicInt32=0x%x\n", PcdGet32(PcdDynamicInt32)); + } else { + Print(L"PcdDynamicInt32 token is unassigned\n"); + } Print(L"PcdDynamicExInt32=%x\n", PcdGetEx32(&gUefiLessonsPkgTokenSpaceGuid, PcdDynamicExInt32)); PcdSetEx32S(&gUefiLessonsPkgTokenSpaceGuid, PcdDynamicExInt32, 0x77777777); |