Serial read not working correctly on Linux

[NomAnor]

I'm trying the program on Arch Linux and it seems the Linux COM_Read read function is not working correctly. From debugging it with strace, I could see that the read() call only returns one byte instead of three and the remaining spill over to the next write/read pair.

write(1, "INFO: STCS to 0x03\n", 19INFO: STCS to 0x03
)    = 19
write(3, "U\303\10", 3)                 = 3
read(3, "U", 3)                         = 1
write(1, "INFO: STCS to 0x02\n", 19INFO: STCS to 0x02
)    = 19
write(3, "U\302\200", 3)                = 3
read(3, "\303", 3)                      = 1
write(1, "INFO: LDCS from 0x00\n", 21INFO: LDCS from 0x00
)  = 21
write(3, "U\200", 2)                    = 2
read(3, "\10", 2)                       = 1
read(3, "U", 1)                         = 1
write(1, "INFO: UPDI init OK\n", 19INFO: UPDI init OK
)    = 19

read() can return less than the given length of bytes, so the read call must be run in a loop until the expected bytes are received or an error occurs or the timeout expires.

I'm still testing but if I get everything working, I will try to create a pull request.