[Buildroot] [PATCH v3] tpm2-tools: drop dependency on tpm2-abrmd

[Peter Korsgaard <peter@korsgaard.com>]

tpm2-tools is commonly used with the resource manager, tpm2-abrmd - But it
CAN be used without, E.G. by setting the TPM2TOOLS_TCTI_NAME environment
variable to communicate directly with the kernel driver:

export TPM2TOOLS_TCTI_NAME=device

Either directly with the TPM device (/dev/tpmN) or through the in-kernel
resource manager provided by Linux kernel since 4.12 (/dev/tpmrmN)

For some use cases (E.G. initramfs) it makes sense to use tpm2-tools
without abrmd, so remove the tpm2-abrmd select, and instead a note in the
help text that it may be needed.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
Changes since v2:
- Drop the imply and instead add a comment as suggested by Yann and Arnout

 package/tpm2-tools/Config.in | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/package/tpm2-tools/Config.in b/package/tpm2-tools/Config.in
index cc87e2a1bf..d8660a8f71 100644
--- a/package/tpm2-tools/Config.in
+++ b/package/tpm2-tools/Config.in
@@ -8,7 +8,6 @@ config BR2_PACKAGE_TPM2_TOOLS
 	select BR2_PACKAGE_LIBCURL
 	select BR2_PACKAGE_LIBGLIB2
 	select BR2_PACKAGE_OPENSSL
-	select BR2_PACKAGE_TPM2_ABRMD # run-time
 	select BR2_PACKAGE_TPM2_TSS
 	help
 	  TPM (Trusted Platform Module) 2.0 CLI tools based on system
@@ -17,6 +16,11 @@ config BR2_PACKAGE_TPM2_TOOLS
 	  and manage non-volatile storage through a TPM2.0 HW
 	  implementation.
 
+	  Notice: An in-kernel resource manager is provided by the
+	  Linux kernel since 4.12. Depending on use cases and kernel
+	  version, the user space resource manager provided by
+	  tpm2-abrmd may be needed.
+
 	  https://github.com/tpm2-software/tpm2-tools
 
 comment "tpm2-tools needs a toolchain w/ dynamic library, wchar, threads"
-- 
2.11.0