4f3c8d6edd
Add 'struct usbtmc_file_data' for each file handle to cache last srq_byte (=Status Byte with SRQ) received by usbtmc_interrupt(..) usbtmc488_ioctl_read_stb returns cached srq_byte when available for each file handle to avoid race conditions of concurrent applications. SRQ now sets EPOLLPRI instead of EPOLLIN since EPOLLIN is now reserved for asynchronous reads Tested-by: Dave Penkler <dpenkler@gmail.com> Reviewed-by: Steve Bayless <steve_bayless@keysight.com> Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>