Changing the number of SR_ERR_SAMPLERATE is not a problem ATM, as we
never had a public release of libsigrok, i.e. nobody relies on the API yet.
#define SR_OK 0 /* No error */
#define SR_ERR -1 /* Generic/unspecified error */
#define SR_ERR_MALLOC -2 /* Malloc/calloc/realloc error */
-#define SR_ERR_SAMPLERATE -3 /* Incorrect samplerate */
+#define SR_ERR_ARG -3 /* Function argument error */
+#define SR_ERR_SAMPLERATE -4 /* Incorrect samplerate */
#define SR_MAX_NUM_PROBES 64 /* Limited by uint64_t. */
#define SR_MAX_PROBENAME_LEN 32