On Thu, Jul 19, 2018 at 08:52:32AM -0700, Tadeusz Struk wrote: > Currently to read a response from the TPM device an application needs > provide "big enough" buffer for the whole response and read it in one go. > The application doesn't know how big the response it beforehand so it > always needs to maintain a 4K buffer and read the max (4K). > In case if the user of the TSS library doesn't provide big enough buffer > the TCTI spec says that the library should set the required size and return > TSS2_TCTI_RC_INSUFFICIENT_BUFFER error code so that the application could > allocate a bigger buffer and call receive again. > To make it possible in the TSS library this requires being able to do > partial reads from the driver. > The library would read the header first to get the actual size of the > response from the header and then read the rest of the response. > This patch adds support for partial reads. > > The usecase is implemented in this TSS commit: > https://github.com/tpm2-software/tpm2-tss/commit/ce982f67a67dc08e24683d30b05800648d8a264c > > Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxx> For non-blocking operation I see the benefit because it does not break the ABI and it really simplifies threading in the user space. In this case I do not have any major evidence of any major benefit *and* the change breaks the ABI. Linux does not *have* to implement in kernel level every tidbit of the TCG spec but it *can* provide support in places where it makes sense and things do not break. /Jarkko
