How to port brcmnand Linux driver?

How to port brcmnand Linux driver?

[Eric Le Bihan]

Hi!

I'm trying to port the brcmnand driver for Broadcom NAND controller from Linux.
This driver requires an update of the MTD headers in barebox, as they lack 
definitions for functions such as mtd_set_ooblayout().

What is the recommended strategy for this? Should I update the whole set of
headers and report the barebox specific changes (use of device_d, etc) or only
add the missing functions?

In general, when adding such driver, should the functions unsupported by barebox
(irq handling, memory barriers, etc) be stubbed or removed?

Best regards,

--
ELB

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Re: How to port brcmnand Linux driver?

[Sascha Hauer]

On Wed, Sep 21, 2016 at 10:40:43AM +0200, Eric Le Bihan wrote:
> Hi!
> 
> I'm trying to port the brcmnand driver for Broadcom NAND controller from Linux.
> This driver requires an update of the MTD headers in barebox, as they lack 
> definitions for functions such as mtd_set_ooblayout().
> 
> What is the recommended strategy for this? Should I update the whole set of
> headers and report the barebox specific changes (use of device_d, etc) or only
> add the missing functions?

For the mtd headers we usually only port the functions we need which
worked good enough in the past.

> 
> In general, when adding such driver, should the functions unsupported by barebox
> (irq handling, memory barriers, etc) be stubbed or removed?

It's a matter of taste. I usually remove spin_locks and other things
that are not relevant for barebox, but we actually do have stubs for some
stuff. I recommend removing such functions, but in the end it's up to
you.

irq handling is normally an area which must be changed heavily anyway when
porting from Linux to barebox, so I wouldn't try to make it look like in
the Linux driver, just to make potential updates from a newer Linux driver
easier.

Sascha

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Re: How to port brcmnand Linux driver?

[Eric Le Bihan]

> On Wed, Sep 21, 2016 at 10:40:43AM +0200, Eric Le Bihan wrote:
> >
> > I'm trying to port the brcmnand driver for Broadcom NAND controller
> > from Linux.
> > This driver requires an update of the MTD headers in barebox, as
> > they lack
> > definitions for functions such as mtd_set_ooblayout().
> > 
> > What is the recommended strategy for this? Should I update the
> > whole set of
> > headers and report the barebox specific changes (use of device_d,
> > etc) or only
> > add the missing functions?
> 
> For the mtd headers we usually only port the functions we need which
> worked good enough in the past.

OK. I've noticed that the use of mtd_set_ooblayout() was introduced in 
Linux 4.7. So I'll port brcmnand from 4.6, thus avoiding quite a few 
changes in the OOB/ECC management.

Thanks for your advices.

Best regards,

--
ELB

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