In U-boot, serial_tstc was use to determine is there have a character in
serial console that pending for read. If there is no "pending" function
implemented in serial driver, the serial-uclass will return "true(1)"
to indicate there have a character pending to read.
Thus, read a character from nulldev serial will result in continuous
getting -EAGAIN return which might lead system to hang.
This commit is to fix a bug in nulldev serial which implement "pending"
function in nulldev serial to always indicate there is no character in
console that pending for read.
Signed-off-by: Wilson Lee <wilson.lee@ni.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Keng Soon Cheah <keng.soon.cheah@ni.com>
Cc: Chen Yee Chew <chen.yee.chew@ni.com>
Cc: Bin Meng <bmeng.cn@gmail.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>
