Commit Graph

40 Commits

Author SHA1 Message Date
Bjarki Arge Andreasen 1dab746dc6 drivers: modem: add at shell
Add AT shell which uses the newly exposed pipes to
send/receive at commands from the modem identified by the
chosen node zephyr,at-shell.

To send an AT command, the shell command at is used, followed
by the command to send, and an optional response which
overwrites the default "OK"

For example, sending "AT", which returns "OK"
  modem at at <- command
  OK <- response

Enabling echo, then sending "AT" which will now return "AT" + "OK"
  modem at ati1 <- command
  OK <- response
  at at <- command
  at <- response
  OK <- response

Signed-off-by: Bjarki Arge Andreasen <bjarki@arge-andreasen.me>
2024-06-10 15:12:34 -05:00
Chris Friedt bc4374b5fe posix: deprecate POSIX_MAX_FDS and add POSIX_DEVICE_IO
The POSIX_MAX_FDS option does not correspond to any standard
POSIX option. It was used to define the size of the file
descriptor table, which is by no means exclusively used by
POSIX (also net, fs, ...).

POSIX_MAX_FDS is being deprecated in order to ensure that
Zephyr's POSIX Kconfig variables correspond to those defined in
the specification, as of IEEE 1003.1-2017. Namely,
POSIX_OPEN_MAX. CONFIG_POSIX_MAX_OPEN_FILES is being deprecated
for the same reason.

To mitigate any possible layering violations, that option is
not user selectable. It tracks the newly added
CONFIG_ZVFS_OPEN_MAX option, which is native to Zephyr.

With this deprecation, we introduce the following Kconfig
options that map directly to standard POSIX Option Groups by
simply removing "CONFIG_":

* CONFIG_POSIX_DEVICE_IO

Similarly, with this deprecation, we introduce the following
Kconfig options that map directly to standard POSIX Options by
simply removing "CONFIG":

* CONFIG_POSIX_OPEN_MAX

In order to maintain parity with the current feature set, we
introduce the following Kconfig options.

* CONFIG_POSIX_DEVICE_IO_ALIAS_CLOSE
* CONFIG_POSIX_DEVICE_IO_ALIAS_OPEN
* CONFIG_POSIX_DEVICE_IO_ALIAS_READ
* CONFIG_POSIX_DEVICE_IO_ALIAS_WRITE

Gate open(), close(), read(), and write() via the
CONFIG_POSIX_DEVICE_IO Kconfig option and move
implementations into device_io.c, to be conformant with the
spec.

Lastly, stage function names for upcoming ZVFS work, to be
completed as part of the LTSv3 Roadmap (e.g. zvfs_open(), ..).

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>
2024-06-04 16:27:12 -05:00
Bjarki Arge Andreasen e79428cda8 drivers: modem: remove gsm_ppp.c device driver
Remove the deprecated gsm_ppp.c device driver and associated
dts compatible.

Signed-off-by: Bjarki Arge Andreasen <bjarki@arge-andreasen.me>
2024-05-29 10:49:08 -07:00
Alessio Lei 733b81d2c7 drivers: modem: remove dependency of modem_socket
Fixed Kconfig to remove dependency between modem_socket and
modem_context, the two do not depend on each other and
should be possible to use independently

Signed-off-by: Alessio Lei <alelei94@yahoo.it>
2023-12-14 09:31:51 +01:00
Bjarki Arge Andreasen b14c39f2c1 drivers/modem: Add generic cellular modem driver
The added cellular modem driver is a naive driver, which
shall serve as a template for implementing tailored
drivers for modems like the UBLOX-R4. It uses only
generic at commands, described in 3gpp, and protocols,
like CMUX and PPP.

A binding for the BG95 has been added, which replaces
the quectel,bg9x. This is neccesary since the BG95 does
not have a usable reset pin, the reset and powerkey are
internally connected to each other.

Signed-off-by: Bjarki Arge Andreasen <baa@trackunit.com>
2023-08-30 13:48:51 +02:00
Willian Wang b7a4a927de drivers: modem: Remove unnecessary MODEM_SHELL dependency
MODEM_SIM_NUMBERS and MODEM_CELL_INFO don't depend on MODEM_SHELL.

Signed-off-by: Willian Wang <git@willian.wang>
2023-08-04 19:35:39 +00:00
Henrik Brix Andersen c41dd36de2 drivers: kconfig: unify menuconfig title strings
Unify the drivers/*/Kconfig menuconfig title strings to the format
"<class> [(acronym)] [bus] drivers".

Including both the full name of the driver class and an acronym makes
menuconfig more user friendly as some of the acronyms are less well-known
than others. It also improves Kconfig search, both via menuconfig and via
the generated Kconfig documentation.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>
2023-03-28 15:06:06 +02:00
Bjarki Arge Andreasen 52dd2bb3a3 drivers/modem: Patch fix for sock id and fd
There is is an error in the way that the sock id is
determined. A unique fd is reserved and assigned appropriatly, but
the id, which should correspond to a socket number within the modem,
is set to an invalid, and identical for all sockets, value, and then
not used appropriatly in the drivers, instead, the sock_fd is used,
which can be any value really, it is not related to the socket number
in any way.

This results in the drivers only working if the reserved fd happens
to be between base_socket_num and (socket_len - 1)

This patch assignes the id to the index of the socket + the
base_socket_num, the socket at index 0 will get the id 1 if the
base_socket_num is 1, and the modem_socket_from_id should then
be used to get a pointer to the socket, since the id is not
neccesarily equal to the index.

The FIXME has been solved by adding a note both at the start
of the modem_socket_get function and inside the Kconfig file
for the MODEM_SOCKET option description. It is not an error,
but the user must be aware that it uses the POSIX file
descriptors, for which only 4 are allocated by default.

This patch fixes the bug, without breaking the brittle modem
drivers which currently are built around this bug.

The modem drivers should be updated to use the id as the
socket num instead of the sock_fd after this fix has been merged.

The "socket # needs assigning" has been removed, as that is what
this patch is doing

I also added comments to the id and sock_fd in the modem_socket
structure to help developers use the id and fd appropriately.

Signed-off-by: Bjarki Arge Andreasen <bjarkix123@gmail.com>
2022-07-14 16:23:33 +02:00
Jordan Yates 95d8deb572 modem: modem_iface_uart_async: added
Adds a communications backend based on the asynchronous UART API,
instead of the interrupt-driven UART API. The primary advantage of this
backend is an improved robustness to dropping bytes under high interrupt
or critical section loads.

Under all loads system efficiency is improved by:
 * Reducing the time spent writing out individual bytes.
 * Reducing the number of UART interrupts fired.
 * Waking up the RX thread much less often.

When utilising this backend over `nordic,nrf-uarte` on a nRF52840, the
baudrate of an esp-at modem could be pushed to at least 921600 without
dropping bytes, compared to a maximum of 230400 with the interrupt API.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>
2022-05-10 10:44:04 +02:00
Jordan Yates 5228de3af5 modem: choice symbol for UART backend
Add a choice symbol that is used to select which UART backend to use.
This allows backends that don't use the interrupt API to be implemented.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>
2022-05-10 10:44:04 +02:00
Gerard Marull-Paretas dffaf5375c kconfig: tweak Kconfig prompts
Tweak some Kconfig prompts after the removal of "Enable...".

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
2022-03-09 15:35:54 +01:00
Gerard Marull-Paretas 95fb0ded6b kconfig: remove Enable from boolean prompts
According to Kconfig guidelines, boolean prompts must not start with
"Enable...". The following command has been used to automate the changes
in this patch:

sed -i "s/bool \"[Ee]nables\? \(\w\)/bool \"\U\1/g" **/Kconfig*

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
2022-03-09 15:35:54 +01:00
Lukas Gehreke 53dea67733 drivers: modem: Added simcom sim7080 modem driver.
Implemented driver for the simcom sim7080 modem.
This driver features Socket offloading, TCP, UDP, DNS,
SMS, GPS and FTP.

Signed-off-by: Lukas Gehreke <lk.gehreke@gmail.com>
2021-12-20 17:48:47 +01:00
Torsten Rasmussen bd61122aa2 kconfig: drivers: experimental settings now uses select EXPERIMENTAL
With the introduction of `EXPERIMENTAL` and `WARN_EXPERIMENTAL` in
Zephyr all drivers settings having `[EXPERIMENTAL]` in their
prompt has has been updated to include `select EXPERIMENTAL` so that
developers can enable warnings when experimental features are enabled.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
2021-10-25 10:46:48 +02:00
Hans Wilmers 120b2165ec drivers: modem: implement operator id and cell info
Implement numerical network operator id, location area code (LAC)
and cell id in modem context and modem shell.

Please note that the functionality to query these values must be
implemented in the modem driver.

Signed-off-by: Hans Wilmers <hans@wilmers.no>
2021-06-14 15:19:13 +02:00
Bilal Wasim 503a70a40a drivers: modem: Add support for quectel bg95
Adding support for Quectel BG95 Modem offloaded driver
to zephyr.

The driver currently implements only the
client side functions of the "socket_op_vtable", and
so cannot be used for cases where Zephyr acts as a
server. Moreover the driver only supports TCP for now.

Looking through the guides, the same driver should be
usable for BG96 (and other modems) except for the modem
boot-up sequence. Hence its named as "bg9x" instead of
"bg95".

Tested extensively with Zephyr acting as MQTT endpoint
and publishing / subscribing data to / from an MQTT
broker.

Signed-off-by: Bilal Wasim <bilalwasim676@gmail.com>
2020-12-01 17:43:59 -05:00
Ryan Erickson eca8842b67 drivers: modem: add Sierra Wireless HL7800 Modem Driver
The driver utilizes the CONFIG_NET_OFFLOAD setting to avoid the
normal handling of IP packets, and instead uses a socket-like
UART interface to handle incoming and outgoing data via AT commands.

Signed-off-by: Ryan Erickson <ryan.erickson@lairdconnect.com>
2020-08-31 10:46:33 +02:00
Göran Weinholt 1ccc65a9c9 drivers: modem: Get the IMSI and ICCID from the SIM
This adds an option to query the modem for the SIM's IMSI and ICCID
numbers, just like the modem's IMEI is queried today. This requires
the SIM to be present, which might not be the case for all
applications, so it can be disabled.

Signed-off-by: Göran Weinholt <goran.weinholt@endian.se>
Signed-off-by: Benjamin Lindqvist <benjamin.lindqvist@endian.se>
2020-08-18 09:39:49 +02:00
Carles Cufi 94861a438b drivers: modem: Port to new timeout API
Port the internal modem API to the new timeout API, using the native
k_timeout_t.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
2020-05-07 11:01:55 +02:00
Johan Hedberg 71eb56a34c net: buf: Move LEGACY_TIMEOUT_API selection to specific subsystems
The net_buf subsystem is now fully compatible with the new timeout
API, so move the selection of the legacy API to those specific
subsystems that use net_buf and still need converting.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
2020-04-03 23:17:53 +03:00
Patrik Flykt 2308293d89 drivers: modem: Support GSM modems and PPP
Create a driver for GSM modems that use a standard AT command set
and enable Zephyr's own PPP stack for IP traffic.

Signed-off-by: Patrik Flykt <patrik.flykt@intel.com>
2020-01-28 12:44:17 +02:00
Ulf Magnusson bd6e04411e kconfig: Clean up header comments and make them consistent
Use this short header style in all Kconfig files:

    # <description>

    # <copyright>
    # <license>

    ...

Also change all <description>s from

    # Kconfig[.extension] - Foo-related options

to just

    # Foo-related options

It's clear enough that it's about Kconfig.

The <description> cleanup was done with this command, along with some
manual cleanup (big letter at the start, etc.)

    git ls-files '*Kconfig*' | \
        xargs sed -i -E '1 s/#\s*Kconfig[\w.-]*\s*-\s*/# /'

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-04 17:31:27 -05:00
Michael Scott f5c45c2946 drivers: modem: introduce socket helper layer
Many modems implement socket-based APIs to manage data connections.
This layer provides much of the groundwork for keeping track of
these "sockets" throughout their lifecycle (from the initial offload
API calls through the command handler call back layers):
- structure for holding socket data like IP protocol, destination,
  source and incoming packet sizes
- configuration to note modem starting socket id and number of
  sockets
- methods to get/put socket structs from/to the pool
- function to update the # and size of packets in the modem receive
  queue
- prebuilt modem_socket_poll() method for socket offload poll() API

Example modem driver setup code looks like this:

/* socket data */
static struct modem_socket_config socket_config;
static struct modem_socket sockets[MDM_MAX_SOCKETS];

static int modem_init(struct device *dev)
{
  ...
  /* setup socket config */
  socket_config.sockets = &sockets[0];
  socket_config.sockets_len = ARRAY_SIZE(sockets);
  socket_config.base_socket_num = 0;
  ret = modem_socket_init(&socket_config);
  ...
}

Signed-off-by: Michael Scott <mike@foundries.io>
2019-08-10 00:03:39 +02:00
Michael Scott 02abddccd6 drivers: modem: cmd handler: introduce cmd handler driver layer
This is a generic command handler implementation which uses the
supplied modem interface to process incoming data and hand it
back to the modem driver via callbacks defined for:
- modem responses
- unsolicited messages
- specified handlers for current operation

The individual modem drivers define functions as command handlers
via the MODEM_CMD_DEFINE() macro.

To use these handlers, a modem operation defines a series of
modem_cmd structures and passes them to the modem_cmd_send()
function.  The modem_cmd includes data for:
- a matching string for when to execute the handler
- # of parameters to parse after the matching string
- delimeters for the parameters

Example modem driver setup code looks like this:

/* create modem context object */
static struct modem_context mctx;

/* net_buf receive pool */
NET_BUF_POOL_DEFINE(mdm_recv_pool, MDM_RECV_MAX_BUF,
		    MDM_RECV_BUF_SIZE, 0, NULL);

/* modem cmds */
static struct modem_cmd_handler_data cmd_handler_data;
static u8_t cmd_read_buf[MDM_RECV_BUF_SIZE];
static u8_t cmd_match_buf[MDM_RECV_BUF_SIZE];

/* modem response handlers */
static struct modem_cmd response_cmds[] = {
	MODEM_CMD("OK", on_cmd_ok, 0U, ""),
	MODEM_CMD("ERROR", on_cmd_error, 0U, ""),
	MODEM_CMD("+CME ERROR: ", on_cmd_exterror, 1U, ""),
};

/* unsolicited handlers */
static struct modem_cmd unsol_cmds[] = {
	MODEM_CMD("+UUSOCL: ", on_cmd_socknotifyclose, 1U, ""),
	MODEM_CMD("+UUSORD: ", on_cmd_socknotifydata, 2U, ","),
	MODEM_CMD("+UUSORF: ", on_cmd_socknotifydata, 2U, ","),
	MODEM_CMD("+CREG: ", on_cmd_socknotifycreg, 1U, ""),
};

/* setup cmd handler data */
cmd_handler_data.cmds[CMD_RESP] = response_cmds;
cmd_handler_data.cmds_len[CMD_RESP] = ARRAY_SIZE(response_cmds);
cmd_handler_data.cmds[CMD_UNSOL] = unsol_cmds;
cmd_handler_data.cmds_len[CMD_UNSOL] = ARRAY_SIZE(unsol_cmds);
cmd_handler_data.read_buf = &cmd_read_buf[0];
cmd_handler_data.read_buf_len = sizeof(cmd_read_buf);
cmd_handler_data.match_buf = &cmd_match_buf[0];
cmd_handler_data.match_buf_len = sizeof(cmd_match_buf);
cmd_handler_data.buf_pool = &mdm_recv_pool;
cmd_handler_data.alloc_timeout = BUF_ALLOC_TIMEOUT;
ret = modem_cmd_handler_init(&mctx.cmd_handler, &cmd_handler_data);

Signed-off-by: Michael Scott <mike@foundries.io>
2019-08-10 00:03:39 +02:00
Michael Scott d56a05f7a7 drivers: modem: interface: introduce UART interface driver layer
The UART-based modem interface layer implements the modem context
interface for Zephyr's UART APIs.  This driver closely resembles
the existing modem receiver, but conforming to the modem interface
agreements.

Example modem driver setup code looks like this:

/* create modem context object */
static struct modem_context mctx;

/* create uart interface data object and buffers */
static struct modem_iface_uart_data iface_data;
static u8_t iface_isr_buf[MDM_RECV_BUF_SIZE];
static u8_t iface_rb_buf[MDM_MAX_DATA_LENGTH];

iface_data.isr_buf = &iface_isr_buf[0];
iface_data.isr_buf_len = sizeof(iface_isr_buf);
iface_data.rx_rb_buf = &iface_rb_buf[0];
iface_data.rx_rb_buf_len = sizeof(iface_rb_buf);
ret = modem_iface_uart_init(&mctx.iface, &iface_data,
			    UART_DEV_NAME);

Signed-off-by: Michael Scott <mike@foundries.io>
2019-08-10 00:03:39 +02:00
Michael Scott 90e778d983 drivers: modem: context helper: introduce modem context helper driver
Initial support for modems in Zephyr use the following driver model:
- Main portions of code live in the modem specific driver.
  This includes internal socket management, command parsing, etc.
- They leverage a UART-based modem receiver helper to gather data.
- Interface with Zephyr networking via net_context offload APIs.

This implementation was good enough to kick start interest in
supporting modem usage in Zephyr, but lacks future scalability:
- The net_context offload APIs don't allow for operations such
  as offloaded DNS, SSL/TLS and other HW specific features.
- Since most of the code lives within the modem drivers, it's
  very hard for the Zephyr community to improve the driver layer
  over time.  Bugs found in 1 driver probably affect others due
  to copy/paste method of development.
- Lack of abstraction for different modem interfaces and command
  handlers makes it impossible to write a "dummy" layer which
  could be used for testing.
- Lack of centralized processing makes implementing low power modes
  and other advanced topics more difficult.

Introducing the modem context helper driver and sub-layers:
- modem context helper acts as an umbrella for several configurable
  layers and exposes this data to externals such as the modem shell.
  Included in the helper is GPIO pin config functions which are
  currently duplicated in most drivers.
- modem interface layer: this layer sits on the HW APIs for the
  peripheral which communicates with the modem.  Users of the modem
  interface can handle data via read/write functions.  Individual
  modem drivers can select from (potentially) several modem
  interfaces.
- modem command parser layer: this layer communicates with the
  modem interface and processes the data for use by modem drivers.

Fixes: https://github.com/zephyrproject-rtos/zephyr/issues/17922

Signed-off-by: Michael Scott <mike@foundries.io>
2019-08-10 00:03:39 +02:00
Michael Scott 759d1d6408 drivers: modem: introduce u-blox SARA-R4 modem driver
The u-blox SARA-R4 modem modules are Ultra-compact LTE Cat
M1 / NB1 ready:

- Configurable with a single hardware version
- Flexible mode selection as LTE Cat M1, LTE Cat NB1, EGPRS -
  only/preferred
- Low power consumption and longer battery life
- Extended range in buildings, basements, and with NB1,
  underground

This driver introduces support for basic AT commands to
query modem information as well as socket connection
for TCP/UDP communication.

Signed-off-by: Michael Scott <mike@foundries.io>
2019-05-21 08:17:20 -04:00
Michael Scott a4cedf5a0b drivers: modem: remove leftover artifact from wncm14a2a split
In commit c1f24abb13 ("drivers: modem: wistron kconfig separation"),
A single line of the WNC-M14A2A congigs was left in the main modem
Kconfig.

Let's clean up the Kconfig file by removing the left over.

Signed-off-by: Michael Scott <mike@foundries.io>
2019-03-14 08:41:34 +01:00
Georgij Cernysiov c1f24abb13 drivers: modem: wistron kconfig separation
Separates Kconfig to a separate file.

Signed-off-by: Georgij Cernysiov <g.cernysiov@elco-automation.de>
2019-03-01 09:48:12 +01:00
Georgij Cernysiov 94ee0ddbde drivers: modem: receiver: switch to ring buffer from pipe api
Replaces used k_pipe with ring_buffer API which is safe for ISR.

Signed-off-by: Georgij Cernysiov <g.cernysiov@elco-automation.de>
2019-03-01 09:46:48 +01:00
Georgij Cernysiov bed7fb3df0 drivers: modem: modem receiver dependencies adaptation
Moved UART interrupt dependencies from concrete driver to
the modem receiver as it uses UART interrupt functions within.
This allows developing other UART interrupt based modems without
the need to depend on the aforementioned features explicitly.

Signed-off-by: Georgij Cernysiov <g.cernysiov@elco-automation.de>
2019-01-25 17:36:59 -05:00
Michael Scott 39843617cb drivers: modem: WNCM14A2A select UART_INTERRUPT_DRIVEN
Modem driver for WNCM14A2A was erroneously leaving the
selection of UART_INTERRUPT_DRIVEN up to CONSOLE_HANDLER.
Now, with the move to the new SHELL backend, this is no
longer happening.

Let's select it from the modem driver, instead of depending
on it.

Let's also add a dependency on SERIAL_SUPPORT_INTERRUPT
which the serial drivers enable to let us know
UART_INTERRUPT_DRIVEN is available.

Signed-off-by: Michael Scott <mike@foundries.io>
2018-11-21 04:09:23 -06:00
Michael Scott 38bdc9f532 drivers: modem: migrate modem shell to new shell API
Convert modem-shell to use the new shell API.

Signed-off-by: Michael Scott <mike@foundries.io>
2018-10-29 08:40:40 -04:00
Anas Nashif ecc050e69e drivers: modem: move to new logger
Move driver to new logger.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
2018-10-10 10:22:01 -04:00
Mieszko Mierunski 4f6aac1a67 dts: nrf5: Changed GPIO and GPIOTE define names
Changed names using nrf5 to nrf for consistency with other drivers.

Signed-off-by: Mieszko Mierunski <mieszko.mierunski@nordicsemi.no>
2018-08-17 07:29:14 -07:00
Michael Scott 65af15bcc2 boards: arm: nrf52840_pca10056: add settings for WNC-M14A2A modem
These settings enable use of the WNC-M14A2A LTE-M modem as the default
network interface for the nRF52840-DK board (nrf52840_pca10056).

They include the following settings when MODEM_WNCM14A2A is selected:
- UARTE1 pin setup
- DTS / DTS fixup additions for WNC-M14A2A
- Kconfig settings for modem driver

Signed-off-by: Michael Scott <mike@foundries.io>
2018-08-06 10:43:46 +03:00
Michael Scott 01745c3844 boards: arm: frdm_k64f: add settings to use WNC-M14A2A LTE-M modem
These settings enable use of the WNC-M14A2A LTE-M modem as the default
network interface instead of ethernet.

They include the following settings when MODEM_WNCM14A2A is selected:
- UART 2 setup
- Avoid ETH_0 setup due to pin conflicts
- DTS addition for WNC-M14A2A
- Kconfig settings for modem driver

Signed-off-by: Michael Scott <mike@foundries.io>
2018-08-06 10:43:46 +03:00
Michael Scott 8b3d4ab6b8 drivers: modem: add modem shell extension
Add a set of modem shell commands to support modem development.

Start with:
modem list: Lists all registered modems and related information
modem send <modem receiver index> <command>: Send command to modem

Signed-off-by: Michael Scott <mike@foundries.io>
2018-08-06 10:43:46 +03:00
Michael Scott 042d79e86c drivers: modem: add Wistron WNC-M14A2A LTE-M Modem Driver
The WNC-M14A2A (LTE / LTE-M) modem is presented as an Arduino-
compatible shield via AT&T's IoT Starter Kit v1.0.  It was
originally intended to work with the FRDM-K64F board, but
in theory as long as the right pins are configured it can
work with any board that supports Arduino-compatible headers.

The driver utilizes the CONFIG_NET_OFFLOAD setting to avoid the
normal handling of IP packets, and instead uses a socket-like
UART interface to handle incoming and outgoing data.

Signed-off-by: Michael Scott <mike@foundries.io>
2018-08-06 10:43:46 +03:00
Michael Scott 9182d2e59c drivers: modem: add modem receiver (tty) driver
Modem drivers need a fast buffer-based receiver for passing data
back and forth from the UART to the driver.  This provides an
efficient configuarable driver which merely sends and receives
but doesn't process the data, that's left up to the modem driver.

Signed-off-by: Michael Scott <mike@foundries.io>
2018-08-06 10:43:46 +03:00