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Add a generic driver for GNSS receivers with a USB interface with two
bulk endpoints.
The driver currently assumes that the device protocol is NMEA (only) but
this can be generalised later as needed.
Link: https://lore.kernel.org/r/20211220111901.23206-2-johan@kernel.org
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Marc Ferland <ferlandm@amotus.ca>
Signed-off-by: Johan Hovold <johan@kernel.org>
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Add driver for serial-connected Mediatek-based GNSS receivers.
These devices typically boot transmitting vendor specific NMEA output
sequences. The serial port bit rate is read from the device tree
"current-speed".
Note that the driver uses the generic GNSS serial implementation and
therefore essentially only manages power abstracted into three power
states: ACTIVE, STANDBY, and OFF.
For mediatek receivers with a main supply and no enable-gpios, this simply
means that the main supply is disabled in STANDBY and OFF (the optional
backup supply is kept enabled while the driver is bound).
Note that the timepulse-support is left unimplemented.
Signed-off-by: Loys Ollivier <lollivier@baylibre.com>
[ johan: rename backup supply ]
Signed-off-by: Johan Hovold <johan@kernel.org>
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Add driver for serial-connected SiRFstar-based GNSS receivers.
These devices typically boot into hibernate mode from which they can be
woken using a pulse on the ON_OFF input pin. Once active, a pulse on the
same ON_OFF pin is used to put the device back into hibernate mode. The
current state can be determined by sampling the WAKEUP output.
Hardware configurations where WAKEUP has been connected to ON_OFF (and
where an initial WAKEUP pulse during boot is sufficient to have the
device boot into active mode) are also supported. In this case, device
power is managed using the main-supply regulator only.
Note that configurations where WAKEUP is left not connected, so that the
device power state can only indirectly be determined using the I/O
interface, is currently not supported. It should be fairly
straight-forward to extend the current implementation with such support
however (and this this is the main reason for not using the generic
serial implementation for this driver).
Note that timepulse-support is left unimplemented.
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Add driver for serial-connected u-blox GNSS receivers.
Note that the driver uses the generic GNSS serial implementation and
therefore essentially only manages power abstracted into three power
states: ACTIVE, STANDBY, and OFF.
For u-blox receivers with a main supply and no enable-gpios, this simply
means that the main supply is disabled in STANDBY and OFF (the optional
backup supply is kept enabled while the driver is bound).
Note that timepulse-support is not yet implemented.
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Add a generic serial GNSS driver (library) which provides a common
implementation for the gnss interface and power management (runtime and
system suspend). This allows GNSS drivers for specific chip to be
implemented by simply providing a set_power() callback to handle three
states: ACTIVE, STANDBY and OFF.
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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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>
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