Add a "type" device attribute and a "GNSS_TYPE" uevent variable which
can be used to determine the type of a GNSS receiver. The currently
identified types reflect the protocol(s) supported by a receiver:
"NMEA" NMEA 0183
"SiRF" SiRF Binary
"UBX" UBX
Note that both SiRF and UBX type receivers typically support a subset of
NMEA 0183 with vendor extensions (e.g. to allow switching to the vendor
protocol).
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 10f146639fee5ffaf7cf0081c1af518f7d0c533c)
[adelva: dropped changes to drivers that were not backported]
Bug: 146062677
Change-Id: Id272aaa9aa59df41d5d94014edc835f242e719a6
Signed-off-by: Alistair Delva <adelva@google.com>
Add a new subsystem for GNSS (e.g. GPS) receivers.
While GNSS receivers are typically accessed using a UART interface they
often also support other I/O interfaces such as I2C, SPI and USB, while
yet other devices use iomem or even some form of remote-processor
messaging (rpmsg).
The new GNSS subsystem abstracts the underlying interface and provides a
new "gnss" class type, which exposes a character-device interface (e.g.
/dev/gnss0) to user space. This allows GNSS receivers to have a
representation in the Linux device model, something which is important
not least for power management purposes.
Note that the character-device interface provides raw access to whatever
protocol the receiver is (currently) using, such as NMEA 0183, UBX or
SiRF Binary. These protocols are expected to be continued to be handled
by user space for the time being, even if some hybrid solutions are also
conceivable (e.g. to have kernel drivers issue management commands).
This will still allow for better platform integration by allowing GNSS
devices and their resources (e.g. regulators and enable-gpios) to be
described by firmware and managed by kernel drivers rather than
platform-specific scripts and services.
While the current interface is kept minimal, it could be extended using
IOCTLs, sysfs or uevents as needs and proper abstraction levels are
identified and determined (e.g. for device and feature identification).
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 2b6a440351436d792b1960822da4b7d6e673f568)
[adelva: adjusted for drivers/Makefile conflict, __poll_t->unsigned int,
EPOLL* -> POLL* for 4.14]
Bug: 146062677
Change-Id: I5704e952766cd8057fba3be3212091a726e0d85a
Signed-off-by: Alistair Delva <adelva@google.com>
