[U-Boot] [PATCH v2 22/34] env: Add a new implementation of environment access

[Tom Rini]

On Wed, Jul 26, 2017 at 10:32:51AM -0600, Simon Glass wrote:
> Hi Tom,
> 
> On 26 July 2017 at 10:04, Tom Rini <trini at konsulko.com> wrote:
> > On Sun, Jul 23, 2017 at 09:19:57PM -0600, Simon Glass wrote:
> >
> >> We plan to move to a environment access via drivers for each location
> >> where the environment can be stored. Add an implementation for this. So
> >> far it is not used, but will be pressed into service in a future patch.
> >>
> >> Signed-off-by: Simon Glass <sjg at chromium.org>
> > [snip]
> >> +static enum env_location env_get_default_location(void)
> >> +{
> >> +     if IS_ENABLED(CONFIG_ENV_IS_IN_DATAFLASH)
> >> +             return ENVL_DATAFLASH;
> >> +     else 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;
> >> +}
> >
> > I think the kernel has a few examples of how the Kconfig side of things
> > looks so that you can offer N options and then pick a default one (io
> > scheduler, etc).  We should do that rather than alphabetical IS_ENABLED
> > tests.
> 
> Yes it is possible to have a choice in Kconfig, but for this first
> series I have left it as a option. My plan is to allow the environment
> to be in multiple places in the future, e.g. try using mmc and fall
> back to SPI flash. I think that the environment location should be
> able to be a run-time decision.
> 
> What do you think?

I think run-time decision will be helpful, yeah, but we'll still need a
way to say "this is the default place to start from" at build time and
be explicit about it, rather than rely on link order or "first probed"
or whatever.

-- 
Tom
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