Dan Ritter wrote: > OK, either boot to the old kernel and look for an rng kernel > module, The only loaded module with "rng" in its name is "rng_core". That one is present in both kernels, but four TPM-related modules are absent from Linux 6.1: # uname -v #1 SMP Debian 5.10.179-3 (2023-07-27) # lsmod | egrep -i 'rng|tpm' tpm_crb 20480 0 tpm_tis 16384 0 tpm_tis_core 28672 1 tpm_tis tpm 73728 3 tpm_tis,tpm_crb,tpm_tis_core rng_core 16384 3 ccp,tpm # uname -v #1 SMP PREEMPT_DYNAMIC Debian 6.1.38-3 (2023-08-07) # lsmod | egrep -i 'rng|tpm' rng_core 20480 1 ccp And yet /dev/tpm0 exists in both kernels, but disappears when I physically remove the TPM, so the TPM is recognized to some degree even without those modules. Those four TPM-related modules are also present as files under /lib/modules in Linux 5.10, but absent in Linux 6.1. The corresponding source files still exist in the source tree. Have they been disabled in Debian 12? Have they been moved to some "extra modules" package that I haven't found? Or are they just not modules because they're statically built-in? > or identify the rng hardware a little better As I wrote in my first email, it seems to be an Infineon SLB 9665TT2.0. It says "SLB9665TT20" on the chip package. These characters are also written on the package. They mean nothing to me, but maybe they can be used to identify the hardware better: G1946KIV 51ZA947148IA1 (It's extremely difficult to tell I from 1 though.) > and look > for it in the kernel sources at https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/hw_random In that directory I don't see anything that looks relevant. The identifier "tpm-rng-0" comes from tpm_add_hwrng in drivers/char/tpm/tpm-chip.c, which is still there: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/char/tpm/tpm-chip.c?h=v6.1&id=830b3c68c1fb1e9176028d02ef86f3cf76aa2476#n517 Other functions in the same source file create /dev/tpm0, and it looks like the random number generator should get registered together with the TPM. It's conditional on CONFIG_HW_RANDOM_TPM. Where can I check the value of that option? Björn Persson
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