linux-kernel - Re: [PATCH v2 5/5] ARM: use early console instead of early debug in allmodconfig kernels

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Date:	Tue, 28 Oct 2014 14:05:36 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Xia Kaixu <kaixu.xia@...aro.org>
Cc:	arm@...nel.org, arnd@...db.de, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 5/5] ARM: use early console instead of early debug in
 allmodconfig kernels

On Tue, Oct 28, 2014 at 09:31:35PM +0800, Xia Kaixu wrote:
> The early debug could break something when booting 'allmodconfig'
> kernels. So we use early console instead of early debug.
> 
> The early console didn't work yet on OMAP4460 because of missing
> earlycon support and I am working on that.

No. bloody. way.

> @@ -78,7 +78,7 @@ config DEBUG_USER
>  # These options are only for real kernel hackers who want to get their hands dirty.
>  config DEBUG_LL
>  	bool "Kernel low-level debugging functions (read help!)"
> -	depends on DEBUG_KERNEL
> +	depends on DEBUG_KERNEL && !ARCH_MULTIPLATFORM_STRICT

Firstly, this is well advertised that it can only be applied to a single
configuration.  So I don't think we need this dependency here.  Even if
you want to build a strict multiplatform kernel, it should still be
possible to enable this for a specific platform.

It's a developer option, one which requires the developer to engage their
brain before using.

> @@ -1297,6 +1297,29 @@ config EARLY_PRINTK
>  	  kernel low-level debugging functions. Add earlyprintk to your
>  	  kernel parameters to enable this console.
>  
> +config FORCE_EARLY_CONSOLE
> +	bool "Enable all early console drivers"
> +	depends on DEBUG_KERNEL && ARCH_MULTIPLATFORM_STRICT
> +	select TTY
> +	select SERIAL_8250
> +	select SERIAL_8250_CONSOLE
> +	select SERIAL_AMBA_PL011
> +	select SERIAL_AMBA_PL011_CONSOLE
> +	select SERIAL_EARLYCON_ARM_SEMIHOST
> +	select SERIAL_MSM
> +	select SERIAL_MSM_CONSOLE
> +	select SERIAL_XILINX_PS_UART
> +	select SERIAL_XILINX_PS_UART_CONSOLE

Not only will this be a for-ever expanding list, but it'll also continually
suffer from various problems with dependencies.  I absolutely *HATE* the
idea of selecting user visible options like this.

-- 
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.
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