[Linux-parport] [PATCH 1/7] docs: driver-api: parport-lowlevel: clarify purpose of PARPORT_MODE_PCSPP

[Alex Henrie]

On Tue, Mar 12, 2024 at 9:24 AM Daniel Gimpelevich
<daniel at gimpelevich.san-francisco.ca.us> wrote:
>
> That link is to a question that the submitter asked, and nobody
> responded to it. It seems that this patch stems from an incomplete
> reading of the kernel documentation. Those docs say:
>
> > SPP (Standard Parallel Port) functions modify so-called SPP registers:
> > data, status, and control. The hardware may not actually have
> > registers exactly like that, but the PC does and this interface is
> > modelled after common PC implementations. Other low-level drivers may
> > be able to emulate most of the functionality.
>
> So, the PARPORT_MODE_PCSPP flag denotes the availability of the SPP port
> functions, not any fields in a struct.

Hello Daniel, thanks for your reply. I still don't quite understand
what it would mean for a driver to lack PARPORT_MODE_PCSPP. Is the
idea that a parallel port could support EPP or ECP without supporting
SPP? If that's the case then in my opinion the documentation should
still be rewritten, but in a way to clarify that the SPP functions [1]
are not available without the flag, and the flag does not imply low
latency.

-Alex

[1] Namely: read_data, write_data, read_status, read_control,
write_control, frob_control, enable_irq, disable_irq, data_forward,
and data_reverse. See
https://docs.kernel.org/driver-api/parport-lowlevel.html