[U-Boot] [RFC PATCH 06/10] env: Support multiple environments

[Maxime Ripard]

Hi Lukasz, Tom,

On Fri, Nov 17, 2017 at 03:00:15PM +0100, Lukasz Majewski wrote:
> On Fri, 17 Nov 2017 08:41:05 -0500
> Tom Rini <trini at konsulko.com> wrote:
> 
> > On Fri, Nov 17, 2017 at 10:24:37AM +0100, Lukasz Majewski wrote:
> > > Hi Maxime,
> > >   
> > > > Now that we have everything in place to support multiple
> > > > environment, let's make sure the current code can use it.
> > > > 
> > > > The priority used between the various environment is the same one
> > > > that was used in the code previously.
> > > > 
> > > > At read / init times, the highest priority environment is going
> > > > to be detected, and we'll use the same one without lookup during
> > > > writes. This should implement the same behaviour than we
> > > > currently have.
> > > > 
> > > > Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
> > > > ---
> > > >  env/env.c | 75
> > > > ++++++++++++++++++++++++++++++++++++++++++--------------------- 1
> > > > file changed, 50 insertions(+), 25 deletions(-)
> > > > 
> > > > diff --git a/env/env.c b/env/env.c
> > > > index 1d13220aa79b..6af9f897b0ae 100644
> > > > --- a/env/env.c
> > > > +++ b/env/env.c
> > > > @@ -26,33 +26,58 @@ static struct env_driver
> > > > *_env_driver_lookup(enum env_location loc) return NULL;
> > > >  }
> > > >  
> > > > +static enum env_location env_locations[] = {
> > > > +#ifdef CONFIG_ENV_IS_IN_EEPROM
> > > > +	ENVL_EEPROM,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_FAT
> > > > +	ENVL_FAT,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_FLASH
> > > > +	ENVL_FLASH,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_MMC
> > > > +	ENVL_MMC,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_NAND
> > > > +	ENVL_NAND,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_NVRAM
> > > > +	ENVL_NVRAM,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_REMOTE
> > > > +	ENVL_REMOTE,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_SPI_FLASH
> > > > +	ENVL_SPI_FLASH,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_IN_UBI
> > > > +	ENVL_UBI,
> > > > +#endif
> > > > +#ifdef CONFIG_ENV_IS_NOWHERE
> > > > +	ENVL_NOWHERE,
> > > > +#endif
> > > > +	ENVL_UNKNOWN,
> > > > +};
> > > > +
> > > > +static enum env_location env_load_location;
> > > > +
> > > >  static enum env_location env_get_location(enum env_operation op,
> > > > int prio) {
> > > > -	if (prio >= 1)
> > > > -		return ENVL_UNKNOWN;
> > > > -
> > > > -	if IS_ENABLED(CONFIG_ENV_IS_IN_EEPROM)
> > > > -		return ENVL_EEPROM;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_FAT)
> > > > -		return ENVL_FAT;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_FLASH)
> > > > -		return ENVL_FLASH;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_MMC)
> > > > -		return ENVL_MMC;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_NAND)
> > > > -		return ENVL_NAND;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_NVRAM)
> > > > -		return ENVL_NVRAM;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_REMOTE)
> > > > -		return ENVL_REMOTE;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_SPI_FLASH)
> > > > -		return ENVL_SPI_FLASH;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_IN_UBI)
> > > > -		return ENVL_UBI;
> > > > -	else if IS_ENABLED(CONFIG_ENV_IS_NOWHERE)
> > > > -		return ENVL_NOWHERE;
> > > > -	else
> > > > -		return ENVL_UNKNOWN;
> > > > +	switch (op) {
> > > > +	case ENVO_GET_CHAR:
> > > > +	case ENVO_INIT:
> > > > +	case ENVO_LOAD:
> > > > +		if (prio >= ARRAY_SIZE(env_locations))
> > > > +			return -ENODEV;
> > > > +
> > > > +		return env_load_location = env_locations[prio];
> > > > +
> > > > +	case ENVO_SAVE:
> > > > +		return env_load_location;
> > > > +	}
> > > > +
> > > > +	return ENVL_UNKNOWN;
> > > >  }
> > > >  
> > > >  static struct env_driver *env_driver_lookup(enum env_operation
> > > > op, int prio)  
> > > 
> > > I'm just wondering...
> > > 
> > > Do you think that it may be helpful to have a way to force
> > > particular environment to be used (despite of the priority)?  
> > 
> > That's one of the hard parts of this, yes.  I think I had suggested
> > before that we handle that in a follow up series?
> > 
> 
> I don't want to say that this must be done now. I just can imagine that
> we may need such feature in some point.

So I guess this question is also part of the comment Lukasz had on the
other patch.

The current implementation is effectively hardcoding the environment
by doing two things:
  - Rejecting any priority other than 0, which is the highest. It
    basically says to the code that there is no further alternative
    and that its loop should stop there.
  - Returning the first environment in the array.

If one wanted to hardcode the environment to something else than the
default behaviour, you can always implement env_get_location in your
board by doing something like:

enum env_location env_get_location (enum env_operation op, int prio)
{
	if (prio)
		return ENVL_UNKNOWN;

	return ENVL_MMC; /* Or whatever you want */
}

Like I was saying, the default implementation already kind of does
that. Or maybe we want the default one to not hardcode it and just
deal with alternatives?

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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