From mboxrd@z Thu Jan  1 00:00:00 1970
From: James Hogan <james.hogan@imgtec.com>
Subject: Re: What's the deal with the different boot command lines?
Date: Fri, 4 Jan 2013 10:26:42 +0000
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To: Arnd Bergmann <arnd@arndb.de>, Jonas Bonn <jonas.bonn@gmail.com>, Ralf Baechle <ralf@linux-mips.org>, Grant Likely <grant.likely@secretlab.ca>
Cc: linux-arch <linux-arch@vger.kernel.org>, Will <will.newton@imgtec.com>

Ping. Any comments on this?

On 03/12/12 17:08, James Hogan wrote:
> Hi,
> 
> I've been trying to figure out how the various copies of the command
> line are handled and what they're for, to figure out what the best thing
> to do is to avoid getting the same cmdline twice when
> early_init_dt_scan_chosen falls back to CONFIG_CMDLINE. As far as I can
> tell from the generic code:
> 
> setup_arch() is expected to set
> * boot_command_line
> * the pointer pointed to by it's argument (which goes into
> start_kernel()'s command_line variable).
> 
> What is the intention of both of these command lines? Are they supposed
> to be the same, or different, or what?
> 
> boot_command_line:
> * passed to parse_args("early options", ...)
> * gets printed
> * copied to saved_command_line, which is copied to static_command_line
> and used for parsing args at each init level
> 
> command_line:
> * copied to static_command_line first, and passed to parse_args("Booting
> kernel", ...)
> 
> Some interesting architecture's setup_arch() behaviour that I've noticed:
> 
> Openrisc appears to set command_line to CONFIG_CMDLINE, but gets
> boot_command_line from the devicetree chosen.bootargs, which defaults to
> CONFIG_CMDLINE. So it appears that it provides different values. Was
> this intentional?
> 
> MIPS appears to use of_scan_flat_dt to set arcs_cmdline from the
> devicetree (this will default to CONFIG_CMDLINE). CONFIG_CMDLINE may
> then be appended again in arch_mem_init. This is the same problem we
> have with metag. I'm of the opinion that of_scan_flat_dt is doing the
> wrong thing in falling back to CONFIG_CMDLINE, but maybe I misunderstand
> and it just doesn't matter if command line options are repeated. Any
> thoughts?
> 
> Thanks
> James
> 
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