[U-Boot] [PATCH v2 3/3] common: Generic loader for file system

[Chee, Tien Fong]

On Mon, 2018-06-11 at 13:38 -0600, Simon Glass wrote:
> Hi,
> 
> On 11 June 2018 at 08:15, Marek Vasut <marex at denx.de> wrote:
> > 
> > On 06/11/2018 04:13 PM, Chee, Tien Fong wrote:
> > > 
> > > On Mon, 2018-06-11 at 16:03 +0200, Marek Vasut wrote:
> > > > 
> > > > On 06/11/2018 03:55 PM, Chee, Tien Fong wrote:
> > > > [...]
> > > > > 
> > > > > 
> > > > > > 
> > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > Linux firmware loading method is different with this
> > > > > > > > > Linux loading firmware with
> > > > > > > > > 1. Firmware search paths - which is hardcoded in root
> > > > > > > > > file
> > > > > > > > > system
> > > > > > > > > 2. Built-in firmware - part of kernel binaries
> > > > > > > > > 
> > > > > > > > > This patch loading firmware with
> > > > > > > > > 1. Storage type and partition specified in DTS, but
> > > > > > > > > storage
> > > > > > > > > type
> > > > > > > > > can
> > > > > > > > > be overridden dev instance and partition through U-
> > > > > > > > > boot
> > > > > > > > > variable
> > > > > > > > > environment.
> > > > > > > > > 
> > > > > > > > > Or:
> > > > > > > > > 
> > > > > > > > > 2. Storage type can be set through dev instance, and
> > > > > > > > > partition
> > > > > > > > > through
> > > > > > > > > U-boot variable environment. No DTS is required.
> > > > > > > > And why can we not do as Linux does ?
> > > > > > > > 
> > > > > > > Because we don't have root file system, but i have
> > > > > > > mimicked the
> > > > > > > search
> > > > > > > path in our variable environment, but with both storage
> > > > > > > type
> > > > > > > and
> > > > > > > partition.
> > > > > > OK, so user can configure environment variable to inform U-
> > > > > > Boot
> > > > > > where
> > > > > > to
> > > > > > look for firmware, good (although, this probably fails in
> > > > > > early
> > > > > > env,
> > > > > > dunno of that's a problem).
> > > > > > 
> > > > > Without DTS, then you need to configure env variable, so that
> > > > > SPL
> > > > > and
> > > > > U-boot only know what storage type and partiton to look for
> > > > > firmware.
> > > > I guess that's fine ?
> > > > 
> > > Yes, it is already supported in this patches.
> > > > 
> > > > > 
> > > > > 
> > > > > > 
> > > > > > 
> > > > > > But why do we need the DT part of things ? I don't think we
> > > > > > do
> > > > > > need
> > > > > > it
> > > > > > at all.
> > > > > > 
> > > > > Leverage the flexibility and benefits of the DT such as
> > > > > changing
> > > > > both
> > > > > storage type and partitions without changing the codes.
> > > > DT is a hardware description. Does this describe hardware ? No
> > > > 
> > > Okay, then i will remove DT part.
> > Wait for feedback from sjg at least.
> I think using device tree is fine for this, but I suggest that the
> binding file (when you add it) should mention that the node for this
> driver should go in /chosen. That's what we use for settings, etc.
> 
Okay, sure. So, we agree supporting device tree is good to go.

> Things to do:
> - Add a sandbox driver for this uclass, and a test in test/dm/...
> - Add some documentation about it somehwere
> - Add a device-tree binding file - see doc/device-tree-bindings
> 
Okay, let me try.

> Regards,
> Simon