Converting strings to integers

Kernel developers might rightly complain about being confused over which functions should be used to convert strings to integer types. Old functions like simple_strtoul() will silently ignore junk at the end of an integer value, so "100xx" successfully converts to an unsigned integer type. Alternatives like strict_strtoul() have been encouraged instead, but they have problems too, including the lack of overflow checks. So what's a kernel hacker to do?

As of 2.6.39, there is a new set of string-to-integer converters which is expected to be used in preference to all others.

• Unsigned conversions can be done with any of kstrtoull(), kstrtoul(), kstrtouint(), kstrtou64(), kstrtou32(), kstrtou16(), or kstrtou8().

• Conversions to signed integers can be done with kstrtoll(), kstrtol(), kstrtoint(), kstrtos64(), kstrtos32(), kstrtos16(), or kstrtos8().

All of these functions are marked __must_check, so callers are expected to check to ensure that the conversion happened successfully. The older functions are marked deprecated, and will eventually be removed. These new kstrto*() functions are now the Official Best Way To Convert Strings, so developers need wonder no longer.

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