[PATCH] RISC-V: Update Kconfig to better handle CMDLINE

[mick@ics.forth.gr (Nick Kossifidis)]

???? 2018-11-16 19:08, Nick Kossifidis ??????:
> ???? 2018-11-16 18:52, Palmer Dabbelt ??????:
>> On Fri, 09 Nov 2018 17:02:44 PST (-0800), mick at ics.forth.gr wrote:
>>> Add a menu to chose how the built-in command line will be
>>> used and add CMDLINE_EXTEND for compatibility with FDT code.
>>> 
>>> Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>
>>> ---
>>>  arch/riscv/Kconfig | 45 
>>> ++++++++++++++++++++++++---------------------
>>>  1 file changed, 24 insertions(+), 21 deletions(-)
>>> 
>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>>> index 55da93f4e818..81f884164b52 100644
>>> --- a/arch/riscv/Kconfig
>>> +++ b/arch/riscv/Kconfig
>>> @@ -227,39 +227,42 @@ endmenu
>>> 
>>>  menu "Boot options"
>>> 
>>> -config CMDLINE_BOOL
>>> -	bool "Built-in kernel command line"
>>> +config CMDLINE
>>> +	string "Built-in kernel command line"
>>>  	help
>>>  	  For most platforms, it is firmware or second stage bootloader
>>>  	  that by default specifies the kernel command line options.
>>>  	  However, it might be necessary or advantageous to either override
>>> -	  the default kernel command line or add a few extra options to it.
>>> -	  For such cases, this option allows hardcoding command line 
>>> options
>>> -	  directly into the kernel.
>>> +	  the provided kernel command line or add a few extra options to 
>>> it.
>>> +	  For such cases, it is possible to define a built-in command line
>>> +	  here and chose how the kernel should use it later on.
>>> 
>>> -	  For that, choose 'Y' here and fill in the extra boot parameters
>>> -	  in CONFIG_CMDLINE.
>>> +choice
>>> +	prompt "Built-in command line usage" if CMDLINE != ""
>>> +	default CMDLINE_FALLBACK
>>> +	help
>>> +	  Chose how the kernel will handle the provided built-in command
>>> +	  line.
>>> 
>>> -	  The built-in options will be concatenated to the default command
>>> -	  line if CMDLINE_FORCE is set to 'N'. Otherwise, the default
>>> -	  command line will be ignored and replaced by the built-in string.
>>> +config CMDLINE_FALLBACK
>>> +	bool "Fallback"
>>> +	help
>>> +	  Use the built-in command line as fallback in case we get nothing
>>> +	  from the boot loader.
>>> 
>>> -config CMDLINE
>>> -	string "Built-in kernel command string"
>>> -	depends on CMDLINE_BOOL
>>> -	default ""
>>> +config CMDLINE_EXTEND
>>> +	bool "Extension"
>>>  	help
>>> -	  Supply command-line options at build time by entering them here.
>>> +	  Use the built-in command line as an extension of the command line
>>> +	  provided by the boot loader.
>>> 
>>>  config CMDLINE_FORCE
>>> -	bool "Built-in command line overrides bootloader arguments"
>>> -	depends on CMDLINE_BOOL
>>> +	bool "Forced"
>>>  	help
>>> -	  Set this option to 'Y' to have the kernel ignore the bootloader
>>> -	  or firmware command line.  Instead, the built-in command line
>>> -	  will be used exclusively.
>>> +	  Use the built-in command line in place of the command line
>>> +	  provided by the boot loader.
>>> 
>>> -	  If you don't know what to do here, say N.
>>> +endchoice
>>> 
>>>  endmenu
>> 
>> It looks like this is functionally equivalent to what ARM has, but the
>> polarity is a bit different and the help strings aren't as easy to
>> read.  Is there a reason we can't just copy what they do?
>> 
>>    config CMDLINE
>>            string "Default kernel command string"
>>            default ""
>>            help
>>              On some architectures (EBSA110 and CATS), there is 
>> currently no way
>>              for the boot loader to pass arguments to the kernel. For 
>> these
>>              architectures, you should supply some command-line 
>> options at build
>>              time by entering them here. As a minimum, you should 
>> specify the
>>              memory size and the root device (e.g., mem=64M 
>> root=/dev/nfs).
>>       choice
>>            prompt "Kernel command line type" if CMDLINE != ""
>>            default CMDLINE_FROM_BOOTLOADER
>>            depends on ATAGS
>>       config CMDLINE_FROM_BOOTLOADER
>>            bool "Use bootloader kernel arguments if available"
>>            help
>>              Uses the command-line options passed by the boot loader. 
>> If
>>              the boot loader doesn't provide any, the default kernel 
>> command
>>              string provided in CMDLINE will be used.
>>       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.
>>       config CMDLINE_FORCE
>>            bool "Always use the default kernel command string"
>>            help
>>              Always use the default kernel command string, even if the 
>> boot
>>              loader passes other arguments to the kernel.
>>              This is useful if you cannot or don't want to change the
>>              command-line options your boot loader passes to the 
>> kernel.
>>    endchoice
>>    I'm not really opposed to your solution, I'm just trying to avoid
>> being different without a reason.
> 
> ATAGS and references to ARM platforms such as EBSA110 are not related 
> to RISC-V
> and I think CMDLINE_FALLBACK is more descriptive than 
> CMDLINE_FROM_BOOTLOADER.

Now that you mention it the text could be better. I just wanted to
keep them short and consistent. Do you want me to use ARM's text for
CMDLINE_EXTEND and CMDLINE_FORCE ?