Re: [PATCH v7 1/5] of/serial: move earlycon early_param handling to serial

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Mar 31, 2016 at 08:04:20PM +0300, Aleksey Makarov wrote:
> 
> 
> 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@linaro.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@linaro.org>
> >> Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
> >> Acked-by: Rob Herring <robh@kernel.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.

It "exists" in that you return -ENODEV, right?  Look at the place where
you called this function, previously you returned 0, now you return this
function call's return value.

> 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.

I don't understand.

> >  and now you return -ENODEV, did you
> > test this out?
> 
> Yes, I tested it.

On what platforms?  With what configurations?

thanks,

greg k-h