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Subject: Re: [PATCH] powerpc: Support CMDLINE_EXTEND
To:     Chris Packham <Chris.Packham@alliedtelesis.co.nz>,
        "paulus@samba.org" <paulus@samba.org>,
        "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
        "benh@kernel.crashing.org" <benh@kernel.crashing.org>
Cc:     "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20190724053303.24317-1-chris.packham@alliedtelesis.co.nz>
 <59674457-eda5-fe3b-65e0-29c20102fe4d@c-s.fr>
 <1564521015.6123.11.camel@alliedtelesis.co.nz>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <32ae09e8-0d32-4266-aa37-d5a34cb4e707@c-s.fr>
Date:   Wed, 31 Jul 2019 09:23:57 +0200
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Le 30/07/2019 à 23:10, Chris Packham a écrit :
> Hi Christophe,
> 
> On Tue, 2019-07-30 at 09:02 +0200, Christophe Leroy wrote:
>>
>> Le 24/07/2019 à 07:33, Chris Packham a écrit :
>>>
>>> Device tree aware platforms can make use of CMDLINE_EXTEND to
>>> extend the
>>> kernel command line provided by the bootloader. This is
>>> particularly
>>> useful to set parameters for built-in modules that would otherwise
>>> be
>>> done at module insertion. Add support for this in the powerpc
>>> architecture.
>>>
>>> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
>>> ---
>>>    arch/powerpc/Kconfig | 12 ++++++++++++
>> I think you also have to implement some stuff in
>> early_cmdline_parse()
>> in arch/powerpc/kernel/prom_init.c
> 
> I my case I didn't need to since the generic code in drivers/of/fdt.c
> did what I need. For early options or platforms that don't use a device
> tree then I can see why I'd need the update to update to prom_init.
> 
>>
>> Maybe look at https://patchwork.ozlabs.org/patch/1074126/
>>
> 
> Do you mind if I take this and fold it into a v2 of my patch? Any
> particular reason it didn't get picked up in April?

Sure, take it, I don't mind.

Two reasons it was not picked up in April I believe:
- It was part of a larger series 
(https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=100518) 
and was intended to challenge the series proposed by Daniel 
(https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=98106) 
but nothing happened.
- It was conflicting with the ongoing changes for implementing KASAN.

What you will have to do is to define prom_strlcat() in the same spirit 
as https://patchwork.ozlabs.org/patch/1091621/ by copying it from 
lib/string.c and I think you'll be able to drop prom_strlcpy() as that 
function what only used there.

Christophe

> 
>> Christophe
>>
>>>
>>>    1 file changed, 12 insertions(+)
>>>
>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>> index d8dcd8820369..cd9b3974aa36 100644
>>> --- a/arch/powerpc/Kconfig
>>> +++ b/arch/powerpc/Kconfig
>>> @@ -851,6 +851,11 @@ config CMDLINE
>>>    	  some command-line options at build time by entering
>>> them here.  In
>>>    	  most cases you will need to specify the root device
>>> here.
>>>    
>>> +choice
>>> +	prompt "Kernel command line type" if CMDLINE != ""
>>> +	default CMDLINE_FORCE
>>> +	depends on CMDLINE_BOOL
>>> +
>>>    config CMDLINE_FORCE
>>>    	bool "Always use the default kernel command string"
>>>    	depends on CMDLINE_BOOL
>>> @@ -860,6 +865,13 @@ config CMDLINE_FORCE
>>>    	  This is useful if you cannot or don't want to change
>>> the
>>>    	  command-line options your boot loader passes to the
>>> kernel.
>>>    
>>> +config CMDLINE_EXTEND
>>> +	bool "Extend bootloader kernel arguments"
>>> +	help
>>> +	  The command-line arguments provided by the boot loader
>>> will be
>>> +	  appended to the default kernel command string.
>>> +endchoice
>>> +
>>>    config EXTRA_TARGETS
>>>    	string "Additional default image types"
>>>    	help