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

[Chee, Tien Fong <tien.fong.chee@intel.com>]

On Mon, 2018-06-11 at 15:38 +0200, Marek Vasut wrote:
> On 06/11/2018 02:42 PM, Chee, Tien Fong wrote:
> > 
> > On Mon, 2018-06-11 at 13:55 +0200, Marek Vasut wrote:
> > > 
> > > On 06/11/2018 01:53 PM, Chee, Tien Fong wrote:
> > > > 
> > > > 
> > > > On Mon, 2018-06-11 at 11:39 +0200, Marek Vasut wrote:
> > > > > 
> > > > > 
> > > > > On 06/11/2018 07:01 AM, Chee, Tien Fong wrote:
> > > > > [...]
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > This is a configuration. You do not need (new) a DT
> > > > > > > > > compatible
> > > > > > > > > for
> > > > > > > > > that.
> > > > > > > > > So why is the DT compatible even needed in the FW
> > > > > > > > > loader
> > > > > > > > > at
> > > > > > > > > all ?
> > > > > > > > > 
> > > > > > > > I thought DT compatible is used by driver to find the
> > > > > > > > fs_loader
> > > > > > > > node in
> > > > > > > > DTS. May be i am wrong.
> > > > > > > There should be no FW loader in the DTS. Why would there
> > > > > > > be
> > > > > > > one ?
> > > > > > > 
> > > > > >  I added DTS support for user to define storage type and
> > > > > > default
> > > > > > partition. So you want me to remove the DTS?
> > > > > > Removing the DTS, then user can only set storage type and
> > > > > > partition
> > > > > > through dev instance. So, this design OK for you?
> > > > > How does Linux do it ?
> > > > > 
> > > > 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.

> 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.