From: Keng Soon Cheah keng.soon.cheah@ni.com

Some device the serial console's initialization cannot run early during the boot process. Hence, nulldev serial device is helpful on that situation.

For example, if the serial module was implemented in FPGA. Serial initialization is prohibited to run until the FPGA was programmed.

This commit is to adding nulldev serial driver. This will allows the default console to be specified as a nulldev.

Signed-off-by: Joe Hershberger joe.hershberger@ni.com Signed-off-by: Keng Soon Cheah keng.soon.cheah@ni.com Cc: Chen Yee Chew chen.yee.chew@ni.com --- drivers/serial/Kconfig | 7 ++++++ drivers/serial/Makefile | 1 + drivers/serial/serial_nulldev.c | 48 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 56 insertions(+) create mode 100644 drivers/serial/serial_nulldev.c

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig index a8e9978..5064edf 100644 --- a/drivers/serial/Kconfig +++ b/drivers/serial/Kconfig @@ -409,6 +409,13 @@ config MXC_UART If you have a machine based on a Motorola IMX CPU you can enable its onboard serial port by enabling this option.

+config NULLDEV_SERIAL + bool "Null serial device" + help + Select this to enable null serial device support. A null serial + device merely acts as a placeholder for a serial device and does + nothing for all it's operation. + config PIC32_SERIAL bool "Support for Microchip PIC32 on-chip UART" depends on DM_SERIAL && MACH_PIC32 diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile index 72a6996..7adcee3 100644 --- a/drivers/serial/Makefile +++ b/drivers/serial/Makefile @@ -49,6 +49,7 @@ obj-$(CONFIG_BCM283X_MU_SERIAL) += serial_bcm283x_mu.o obj-$(CONFIG_MSM_SERIAL) += serial_msm.o obj-$(CONFIG_MVEBU_A3700_UART) += serial_mvebu_a3700.o obj-$(CONFIG_MPC8XX_CONS) += serial_mpc8xx.o +obj-$(CONFIG_NULLDEV_SERIAL) += serial_nulldev.o

ifndef CONFIG_SPL_BUILD obj-$(CONFIG_USB_TTY) += usbtty.o diff --git a/drivers/serial/serial_nulldev.c b/drivers/serial/serial_nulldev.c new file mode 100644 index 0000000..0768308 --- /dev/null +++ b/drivers/serial/serial_nulldev.c @@ -0,0 +1,48 @@ +/* + * Copyright (c) 2015 National Instruments + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <common.h> +#include <dm.h> +#include <serial.h> + +static int nulldev_serial_setbrg(struct udevice *dev, int baudrate) +{ + return 0; +} + +static int nulldev_serial_getc(struct udevice *dev) +{ + return -EAGAIN; +} + +static int nulldev_serial_input(struct udevice *dev) +{ + return 0; +} + +static int nulldev_serial_putc(struct udevice *dev, const char ch) +{ + return 0; +} + +static const struct udevice_id nulldev_serial_ids[] = { + { .compatible = "nulldev-serial" }, + { } +}; + + +const struct dm_serial_ops nulldev_serial_ops = { + .putc = nulldev_serial_putc, + .getc = nulldev_serial_getc, + .setbrg = nulldev_serial_setbrg, +}; + +U_BOOT_DRIVER(serial_nulldev) = { + .name = "serial_nulldev", + .id = UCLASS_SERIAL, + .of_match = nulldev_serial_ids, + .ops = &nulldev_serial_ops, +};