linux-kernel - Re: [PATCH v7 1/5] of/serial: move earlycon early

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Message-ID: <56FD5894.3060105@linaro.org>
Date:	Thu, 31 Mar 2016 20:04:20 +0300
From:	Aleksey Makarov <aleksey.makarov@...aro.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Russell King <linux@....linux.org.uk>,
	linux-serial@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Al Stone <ahs3@...hat.com>,
	Christopher Covington <cov@...eaurora.org>,
	Yury Norov <ynorov@...iumnetworks.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	"Zheng, Lv" <lv.zheng@...el.com>, Rob Herring <robh+dt@...nel.org>,
	Frank Rowand <frowand.list@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Jiri Slaby <jslaby@...e.com>, devicetree@...r.kernel.org
Subject: Re: [PATCH v7 1/5] of/serial: move earlycon early_param handling to
 serial



On 03/31/2016 07:32 PM, Greg Kroah-Hartman wrote:
> On Thu, Mar 31, 2016 at 04:40:23PM +0300, Aleksey Makarov wrote:
>> From: Leif Lindholm <leif.lindholm@...aro.org>
>>
>> We have multiple "earlycon" early_param handlers - merge the DT one into
>> the main earlycon one.  It's a cleanup that also will be useful
>> to defer setting up DT console until ACPI/DT decision is made.
>>
>> Rename the exported function to avoid clashing with the function from
>> arch/microblaze/kernel/prom.c
>>
>> Signed-off-by: Leif Lindholm <leif.lindholm@...aro.org>
>> Signed-off-by: Aleksey Makarov <aleksey.makarov@...aro.org>
>> Acked-by: Rob Herring <robh@...nel.org>
>> ---
>>  drivers/of/fdt.c              | 11 +----------
>>  drivers/tty/serial/earlycon.c |  2 +-
>>  include/linux/of_fdt.h        |  2 ++
>>  3 files changed, 4 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 3349d2a..b50f775 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -805,7 +805,7 @@ static inline void early_init_dt_check_for_initrd(unsigned long node)
>>  
>>  #ifdef CONFIG_SERIAL_EARLYCON
>>  
>> -static int __init early_init_dt_scan_chosen_serial(void)
>> +int __init early_init_dt_scan_chosen_stdout(void)
>>  {
>>  	int offset;
>>  	const char *p, *q, *options = NULL;
>> @@ -849,15 +849,6 @@ static int __init early_init_dt_scan_chosen_serial(void)
>>  	}
>>  	return -ENODEV;
>>  }
>> -
>> -static int __init setup_of_earlycon(char *buf)
>> -{
>> -	if (buf)
>> -		return 0;
>> -
>> -	return early_init_dt_scan_chosen_serial();
>> -}
>> -early_param("earlycon", setup_of_earlycon);
>>  #endif
>>  
>>  /**
>> diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
>> index 067783f..7aae655 100644
>> --- a/drivers/tty/serial/earlycon.c
>> +++ b/drivers/tty/serial/earlycon.c
>> @@ -209,7 +209,7 @@ static int __init param_setup_earlycon(char *buf)
>>  	 * don't generate a warning from parse_early_params() in that case
>>  	 */
>>  	if (!buf || !buf[0])
>> -		return 0;
>> +		return early_init_dt_scan_chosen_stdout();
>>  
>>  	err = setup_earlycon(buf);
>>  	if (err == -ENOENT || err == -EALREADY)
>> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
>> index 2fbe868..5cfe322 100644
>> --- a/include/linux/of_fdt.h
>> +++ b/include/linux/of_fdt.h
>> @@ -63,6 +63,7 @@ extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
>>  				     int depth, void *data);
>>  extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
>>  				     int depth, void *data);
>> +extern int early_init_dt_scan_chosen_stdout(void);
>>  extern void early_init_fdt_scan_reserved_mem(void);
>>  extern void early_init_fdt_reserve_self(void);
>>  extern void early_init_dt_add_memory_arch(u64 base, u64 size);
>> @@ -91,6 +92,7 @@ extern void early_get_first_memblock_info(void *, phys_addr_t *);
>>  extern u64 of_flat_dt_translate_address(unsigned long node);
>>  extern void of_fdt_limit_memory(int limit);
>>  #else /* CONFIG_OF_FLATTREE */
>> +static inline int early_init_dt_scan_chosen_stdout(void) { return -ENODEV; }
> 
> Doesn't this change the default logic?  Today you are returning 0 if you
> don't have this config option set,

I am not sure I understand this.  Which return value do you mean?

1. early_init_dt_scan_chosen_stdout()

Today if CONFIG_OF_FLATTREE is not set then early_init_dt_scan_chosen_stdout() does not exist.

2. param_setup_earlycon()

Today we have 2 handlers for "earlycon" option.  One (in fdt.c) is for the option without args,
and another (earlycon.c) always expects agrs.  But both return 0 for the opposite cases becasue they
can not check what another hander returns.

Now we have just one handler and it can return correct value.

>  and now you return -ENODEV, did you
> test this out?

Yes, I tested it.

Thank you
Aleksey Makarov

> 
> thanks,
> 
> greg k-h
>