[PATCH] netconsole: various improvements

[Pali Rohár]

On Saturday 18 March 2023 14:46:25 Tony Dinh wrote:
> - When Netconsole is running, stdin/stdout/stderr are set to nc. Reset
> stdin/stdout/stderr to serial (a sane deffault) before booting kernel.

This can be a problematic. serial output does not have to be available
for all devices. For example on Nokia N900 phone is available only
lcd/vga display device.

Also this can break CONSOLE_MUX support when more devices are specified
in stdin/stdout/stderr env variables. With CONSOLE_MUX, output is send
to more than one device. User may set it to both serial and nc or also
to other output (e.g. to lcd like on Nokia N900).

So in my opinion, if "nc" is is going to be turned off then just "nc"
string should be removed from env variable and let all other devices
stay in env variables.

Maybe you can use something like this? (taken from common/usb_kbd.c)

#if CONFIG_IS_ENABLED(CONSOLE_MUX)
	if (iomux_replace_device(stdin, "nc", "nulldev"))
		return 1;
#endif

> - Enable net_timeout when netconsole starts will give a better user
> experience if netconsole server is not running.
> 
> Signed-off-by: Tony Dinh <mibodhi at gmail.com>
> ---
> 
>  boot/bootm.c             | 16 +++++++++++++++-
>  drivers/net/netconsole.c |  2 +-
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/boot/bootm.c b/boot/bootm.c
> index 2eec60ec7b..c4a3aaf1bd 100644
> --- a/boot/bootm.c
> +++ b/boot/bootm.c
> @@ -473,7 +473,21 @@ ulong bootm_disable_interrupts(void)
>  	 */
>  	iflag = disable_interrupts();
>  #ifdef CONFIG_NETCONSOLE
> -	/* Stop the ethernet stack if NetConsole could have left it up */
> +	/*
> +	 * Make sure that the starting kernel message printed out.
> +	 * Reset stdin/out/err back to serial and stop the ethernet
> +	 * stack if NetConsole could have left it up
> +	 */
> +	char *s;
> +	int ret;
> +
> +	s = env_get("stdout");
> +	if (strcmp(s, "nc") == 0) {
> +		printf("\n\nStarting kernel ...\n");
> +		ret = env_set("stdin", "serial");
> +		ret = env_set("stdout", "serial");
> +		ret = env_set("stderr", "serial");
> +	}
>  	eth_halt();
>  #endif
>  
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> index 151bc55e07..2091014918 100644
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -20,7 +20,7 @@ static int input_size; /* char count in input buffer */
>  static int input_offset; /* offset to valid chars in input buffer */
>  static int input_recursion;
>  static int output_recursion;
> -static int net_timeout;
> +static int net_timeout = 1;
>  static uchar nc_ether[6]; /* server enet address */
>  static struct in_addr nc_ip; /* server ip */
>  static short nc_out_port; /* target output port */
> -- 
> 2.30.2
>