Hi,
When running setserial, application issue a TIOCGSERIAL iotcl to get serial setting, then update serial setting with TIOCSSERIAL ioctl. It always failed with TIOCSSERIAL ioctl, for application pass 0xffffffff for iomem_base in serial_struct to kernel. On 32bit rootfs & 64bit kernel, compat_ioctl use 0xffffffff as a magic number to mark invalid pointer for iomem_base in serial_struct when truncating a 64bit pointer into 32bit. Serial driver need recognize this invalid pointer when parsing serial_struct from userspace. Thanks Jiang Lu
