On Mon, Jul 23, 2018 at 02:38:08PM -0700, Tadeusz Struk wrote: > On 07/23/2018 02:13 PM, James Bottomley wrote: > > The current patch does, you even provided a use case in your last email > > (it's do command to get sizing followed by do command with correctly > > sized buffer). > > The example I provided was: #1 send a command, #2 read the response header > (10 bytes), get the actual response size from the header and then #3 read > the full response (response size - size of the header bytes). The proposed patch doesn't clear the data_pending if the entire buffer is not consumed, so of course it is ABI breaking, that really isn't OK. > > However, if you tie it to O_NONBLOCK, it won't because no-one currently > > opens the TPM device non blocking so it's an ABI conformant > > discriminator of the uses. Tying to O_NONBLOCK should be simple > > because it's in file->f_flags. > > I think that it might be an option. Especially that I have this on top of > the async patch. Let's discuss this when Jarkko is back. Maybe you could do this by requiring the userspace to call pread() with a non-zero offset to get the trailing segment of the last executed command and leave normal read/pread(off=0) with the semantics as they have today. Jason
