tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 368094df48e680fa51cedb68537408cfa64b788e commit: d76271d22694e874ed70791702db9252ffe96a4c drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort Subsystem config: h8300-randconfig-m031-20210609 (attached as .config) compiler: h8300-linux-gcc (GCC) 9.3.0 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; Reported-by: Dan Carpenter <dan.carpenter(a)oracle.com&gt; smatch warnings: drivers/gpu/drm/xlnx/zynqmp_dp.c:997 zynqmp_dp_aux_cmd_submit() error: we previously assumed 'buf' could be null (see line 966) vim +/buf +997 drivers/gpu/drm/xlnx/zynqmp_dp.c d76271d22694e8 Hyun Kwon 2018-07-07 949 static int zynqmp_dp_aux_cmd_submit(struct zynqmp_dp *dp, u32 cmd, u16 addr, d76271d22694e8 Hyun Kwon 2018-07-07 950 u8 *buf, u8 bytes, u8 *reply) d76271d22694e8 Hyun Kwon 2018-07-07 951 { d76271d22694e8 Hyun Kwon 2018-07-07 952 bool is_read = (cmd & AUX_READ_BIT) ? true : false; d76271d22694e8 Hyun Kwon 2018-07-07 953 u32 reg, i; d76271d22694e8 Hyun Kwon 2018-07-07 954 d76271d22694e8 Hyun Kwon 2018-07-07 955 reg = zynqmp_dp_read(dp, ZYNQMP_DP_INTERRUPT_SIGNAL_STATE); d76271d22694e8 Hyun Kwon 2018-07-07 956 if (reg & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REQUEST) d76271d22694e8 Hyun Kwon 2018-07-07 957 return -EBUSY; d76271d22694e8 Hyun Kwon 2018-07-07 958 d76271d22694e8 Hyun Kwon 2018-07-07 959 zynqmp_dp_write(dp, ZYNQMP_DP_AUX_ADDRESS, addr); d76271d22694e8 Hyun Kwon 2018-07-07 960 if (!is_read) d76271d22694e8 Hyun Kwon 2018-07-07 961 for (i = 0; i < bytes; i++) d76271d22694e8 Hyun Kwon 2018-07-07 962 zynqmp_dp_write(dp, ZYNQMP_DP_AUX_WRITE_FIFO, d76271d22694e8 Hyun Kwon 2018-07-07 963 buf[i]); ^^^^^^ d76271d22694e8 Hyun Kwon 2018-07-07 964 d76271d22694e8 Hyun Kwon 2018-07-07 965 reg = cmd << ZYNQMP_DP_AUX_COMMAND_CMD_SHIFT; d76271d22694e8 Hyun Kwon 2018-07-07 @966 if (!buf || !bytes) Obviously when bytes is zero then buf is NULL etc... This is false positive so you can ignore it if you want, but another option would be to just check "bytes" here. if (!bytes) is the same as if (!buf). d76271d22694e8 Hyun Kwon 2018-07-07 967 reg |= ZYNQMP_DP_AUX_COMMAND_ADDRESS_ONLY; d76271d22694e8 Hyun Kwon 2018-07-07 968 else d76271d22694e8 Hyun Kwon 2018-07-07 969 reg |= (bytes - 1) << ZYNQMP_DP_AUX_COMMAND_BYTES_SHIFT; d76271d22694e8 Hyun Kwon 2018-07-07 970 zynqmp_dp_write(dp, ZYNQMP_DP_AUX_COMMAND, reg); d76271d22694e8 Hyun Kwon 2018-07-07 971 d76271d22694e8 Hyun Kwon 2018-07-07 972 /* Wait for reply to be delivered upto 2ms */ d76271d22694e8 Hyun Kwon 2018-07-07 973 for (i = 0; ; i++) { d76271d22694e8 Hyun Kwon 2018-07-07 974 reg = zynqmp_dp_read(dp, ZYNQMP_DP_INTERRUPT_SIGNAL_STATE); d76271d22694e8 Hyun Kwon 2018-07-07 975 if (reg & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REPLY) d76271d22694e8 Hyun Kwon 2018-07-07 976 break; d76271d22694e8 Hyun Kwon 2018-07-07 977 d76271d22694e8 Hyun Kwon 2018-07-07 978 if (reg & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REPLY_TIMEOUT || d76271d22694e8 Hyun Kwon 2018-07-07 979 i == 2) d76271d22694e8 Hyun Kwon 2018-07-07 980 return -ETIMEDOUT; d76271d22694e8 Hyun Kwon 2018-07-07 981 d76271d22694e8 Hyun Kwon 2018-07-07 982 usleep_range(1000, 1100); d76271d22694e8 Hyun Kwon 2018-07-07 983 } d76271d22694e8 Hyun Kwon 2018-07-07 984 d76271d22694e8 Hyun Kwon 2018-07-07 985 reg = zynqmp_dp_read(dp, ZYNQMP_DP_AUX_REPLY_CODE); d76271d22694e8 Hyun Kwon 2018-07-07 986 if (reply) d76271d22694e8 Hyun Kwon 2018-07-07 987 *reply = reg; d76271d22694e8 Hyun Kwon 2018-07-07 988 d76271d22694e8 Hyun Kwon 2018-07-07 989 if (is_read && d76271d22694e8 Hyun Kwon 2018-07-07 990 (reg == ZYNQMP_DP_AUX_REPLY_CODE_AUX_ACK || d76271d22694e8 Hyun Kwon 2018-07-07 991 reg == ZYNQMP_DP_AUX_REPLY_CODE_I2C_ACK)) { d76271d22694e8 Hyun Kwon 2018-07-07 992 reg = zynqmp_dp_read(dp, ZYNQMP_DP_REPLY_DATA_COUNT); d76271d22694e8 Hyun Kwon 2018-07-07 993 if ((reg & ZYNQMP_DP_REPLY_DATA_COUNT_MASK) != bytes) d76271d22694e8 Hyun Kwon 2018-07-07 994 return -EIO; d76271d22694e8 Hyun Kwon 2018-07-07 995 d76271d22694e8 Hyun Kwon 2018-07-07 996 for (i = 0; i < bytes; i++) d76271d22694e8 Hyun Kwon 2018-07-07 @997 buf[i] = zynqmp_dp_read(dp, ZYNQMP_DP_AUX_REPLY_DATA); d76271d22694e8 Hyun Kwon 2018-07-07 998 } d76271d22694e8 Hyun Kwon 2018-07-07 999 d76271d22694e8 Hyun Kwon 2018-07-07 1000 return 0; d76271d22694e8 Hyun Kwon 2018-07-07 1001 } --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org