Re: [PATCH] ARM: rpi: add SD card environment support

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Oct 15, 2013 at 01:54:50PM +0200, Andre Heider wrote:
> Hi,
> 
> > +static int rpi_env_init(void)
> > +{
> > +	struct stat s;
> > +	const char *diskdev = "/dev/disk0.0";
> > +	int ret;
> > +
> > +	device_detect_by_name("mci0");
> > +
> > +	ret = stat(diskdev, &s);
> > +	if (ret) {
> > +		printf("no %s. using default env\n", diskdev);
> > +		return 0;
> > +	}
> > +
> > +	mkdir("/boot", 0666);
> > +	ret = mount(diskdev, "fat", "/boot");
> > +	if (ret) {
> > +		printf("failed to mount %s\n", diskdev);
> > +		return 0;
> > +	}
> > +
> > +	default_environment_path = "/boot/barebox.env";
> > +
> > +	return 0;
> > +}
> 
> I was solving the same thing just yesterday ;)
> 
> What I did was to create a env/init/automount script, what's the advantage of this approach?

This approach also sets default_environment_path to /boot/barebox.env so
that loadenv/saveenv works and barebox comes up with the saved
environment.

You could probably do similar with scripts doing something like:

automount -d /boot "detect mci0 && mount /dev/disk0.0 /boot"
loadenv -s /boot/barebox.env /env
/env/bin/init

However, I made the experience that in scripts proper error checking is
hard to archieve and therefore often skipped. Also with C Code a single
git commitish makes the system behaviour clear. When instead scripts are
used which might have been modified by a user, or which might come from
an older barebox version the situation gets much more complex.

I generally try to reduce the usage (or better: necessity) of scripts.
They pretend a high level of flexibility but this comes at the cost of
reduced consistency across different boards (or even different instances
of the same board)

Sascha

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