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.
You should solve this in user space, the kernel API requires a full sized buffer here, the tss library should always provide such an internal buffer and then implement whatever scheme TSS wants by memcpying from that buffer.. Jason
