Re: [RFC PATCH 0/3] UART slave device bus

H. Nikolaus Schaller
2016-08-18T11:18:37Z

> Am 18.08.2016 um 13:10 schrieb Pavel Machek <pavel@ucw.cz>:
>
> Hi!
>
>>> I am actually not convinced that GPS should be represented as
>>> /dev/ttyS0 or similar TTY. It think they deserve their own driver
>>> exposing them as simple character devices. That way we can have a
>>> proper DEVTYPE and userspace can find them correctly. We can also
>>> annotate them if needed for special settings.
>>
>> I would _love_ to see that happen, but what about the GPS line
>> discipline that we have today? How would that match up with a char
>> device driver?
>
> ./drivers/usb/serial/garmin_gps.c ?
>
> Hmm, some cleanups would be welcome there... plus it would be good to
> know what is its interface to userland... it is not easily apparent
> from the code.
>
> Actually, having some kind of common support for GPSes in the kernel
> would be nice. (Chardev that spits NMEA data?

Yes and no. How do you apply tcsetattr to such a device? More or less
by implementing another tty stack?

> ) For example N900 GPS is
> connected over network (phonet) interface, with userland driver
> translating custom protocol into NMEA. Not very nice from "kernel
> should provide hardware abstraction" point of view.

Indeed. In such a case the translation should be done in the kernel.
But it is not necessary for devices that already provide NEMA over UART.
Still user-space should be able to tcsetattr how it wants to see the records
(mainly CR/LF translations).

BR,
Nikolaus