[U-Boot] [RFC PATCH 1/3] add file with a default boot environment based heavily on Stephen Warrens recent tegra work.

[Stephen Warren]

On 02/19/2014 12:10 PM, Tom Rini wrote:
...
>> A generic Linux distro wouldn't be installing a kernel to NAND, but
>> would rather put it into the /boot filesystem. NAND boot is something
>> that'd be best supported by the custom hook we discussed above.
> 
> Wait, why would a generic Linux distro be installing to eMMC but not to
> NAND ?  Not that this series needs to be the final point in the
> discussion and all.

I should point out that I was talking about raw NAND MTD partitions
rather than a NAND device with a regular partition table and normal
filesystems within it.

If the NAND is exposed as a regular block device with a regular
filesystem, then it'd look just like any other block device to a generic
distro installer, and hence it could put /boot there, and this patch (or
future enhancement) could certainly usefully contain a generic
bootcmd_nand that used it.

However, if the NAND has hard-coded MTD partitions, and/or the
partitions have no filesystem but rather contain e.g. a raw
zImage/uImage, then that would require board-/SoC-specific support in
the distro kernel and installer, and hence we wouldn't be talking about
a *generic* installer/distro, and *generic* installers/distros are what
this patch series is all about.

>> The commit description for this commit should have set the scene that
>> this series is all about providing a way for a generic Linux distro to
>> create a generic installable media set that boots the same way across n
>> different boards with U-Boot, and similarly also to set up the installed
>> distro filesystem in a single generic way that can boot on any board it
>> gets installed to. It's all about avoiding board-specific boot options
>> such as NAND, and hence may well not be applicable to boards that
>> primarily/only boot from NAND; they would still need custom distro
>> install media and hooks to set up the installed filesystem.
> 
> Why is NAND special but SATA not, other than desktops often have SATA
> exposed but not NAND?  Even more so when you consider that from the
> Linux side of things, dealing with NAND is dealing with NAND and it's
> not board specific.