On Thu, Jan 28, 2021 at 12:57:12PM +0300, Dan Carpenter wrote: > Hello Michał Mirosław, > > The patch 9517b95bdc46: "Input: elants_i2c - add support for > eKTF3624" from Jan 24, 2021, leads to the following static checker > warning: > > drivers/input/touchscreen/elants_i2c.c:966 elants_i2c_mt_event() > warn: should this be a bitwise negate mask? > > drivers/input/touchscreen/elants_i2c.c [...] > 963 w = buf[FW_POS_WIDTH + i / 2]; > 964 w >>= 4 * (~i & 1); > 965 w |= w << 4; > 966 w |= !w; > ^^^^^^^^ > > This code is just very puzzling. I think it may actually be correct? > The boring and conventional way to write this would be to do it like so: > > if (!w) > w = 1; It could also be written as: w += !w; or: w += w == 0; while avoiding conditional. But, in this case, the warning is bogus. Because w | ~w == all-ones (always), it might as well suggested to write: w = -1; or: w = ~0; making the code broken. Best Regards Michał Mirosław
