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Date:	Wed, 3 Apr 2013 18:12:42 -0700
From:	Marcel Holtmann <marcel@...tmann.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Tim Bird <tim.bird@...sony.com>,
	linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: GPS driver for Linux - kernel or user-space driver?

Hi Greg,

>> I've been approached by a developer at Sony who wants to publish an
>> open source driver for a Sony GPS receiver module.
> 
> What does the device look like?  USB device?  UART?  Something else?
> 
>> I've looked in the kernel source, and only see one standalone GPS
>> driver, for Garmin.  It appears that most GPS support in Linux is done
>> via user-space drivers.  Many GPS hardware modules appear to be
>> accessed via a serial line, or USB/serial port.  The Sony
>> module is pretty much the same, accepting commands and delivering
>> data via a uart from the chip.
>> 
>> I planning to recommend writing a user-space driver (based on
>> gpsd and/or the Android GPS HAL specification).  But I'm worried
>> I'm missing something.  Is this the correct approach, or is there
>> an established kernel API for GPS modules - such that I should
>> recommend that this developer writes a kernel module instead
>> of, or in addition to, the user-space support for the hardware?
> 
> If it's just a uart-like device, just write a serial driver and drive it
> from gpsd.  That way seems to be the simplest and then the kernel just
> becomes a dumb-pipe, which is fine.

the one thing that still bugs me is that detecting an UART with GPS functionality behind it is extremely bad experience. If we could get something like DEVTYPE=gps support for the TTY layer, that would be helpful.

Regards

Marcel

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