Some devices with more than one microcontroller report the firmware
version for each of them, giving us more than four tokens. When that
happens, sigrok aborts, even though it received a valid response.
This happens, for example with the Chroma 61604:
'Chroma ATE,61604,001060,1.25,1.34,1.20'
On a Hameg HMO1024 you get incomplete data because the USB transfer takes
longer than the scpi->read_timeout_ms of 1 second that is defined in
scpi_dev_inst_new(). Therefore reset the timeout in sr_scpi_get_string()
whenever the device sends a partial response.
Use g_malloc0() for small allocations and assume they always
succeed. Simplify error handling in a few places accordingly.
Don't always sanity-check parameters for non-public (SR_PRIV)
functions, we require the developers to invoke them correctly.
This allows further error handling simplifications.
libgpib is the userspace component to linux-gpib's kernel modules that
implement low-level interface drivers.
When libsigrok gets userspace GPIB interface drivers, that backend will
be the "official" scpi_gpib.