Re: [PATCH 2/2] xen: arm: more flexible scheme for specifying early printk device

[Ian Campbell <ian.campbell@citrix.com>]

On Thu, 2015-03-12 at 12:03 +0100, Tim Deegan wrote:
> At 14:11 +0000 on 11 Mar (1426079515), Ian Campbell wrote:
> > +EARLY_PRINTK_brcm           := 8250,0xF040AB00,2
> > +EARLY_PRINTK_dra7           := 8250,0x4806A000,2
> > +EARLY_PRINTK_fastmodel      := pl011,0x1c090000,115200
> > +EARLY_PRINTK_exynos5250     := exynos4210,0x12c20000
> > +EARLY_PRINTK_hip04-d01      := 8250,0xE4007000,2
> > +EARLY_PRINTK_juno           := pl011,0x7ff80000
> > +EARLY_PRINTK_lager          := scif,0xe6e60000
> > +EARLY_PRINTK_midway         := pl011,0xfff36000
> > +EARLY_PRINTK_omap5432       := 8250,0x48020000,2
> > +EARLY_PRINTK_seattle        := pl011,0xe1010000
> > +EARLY_PRINTK_sun6i          := 8250,0x01c28000,2
> > +EARLY_PRINTK_sun7i          := 8250,0x01c28000,2
> > +EARLY_PRINTK_thunderx       := pl011,0x87e024000000
> > +EARLY_PRINTK_vexpress       := pl011,0x1c090000
> > +EARLY_PRINTK_xgene-mcdivitt := 8250,0x1c021000,2
> > +EARLY_PRINTK_xgene-storm    := 8250,0x1c020000,2
> > +EARLY_PRINTK_zynqmp         := cadence,0xff000000
> > +
> > +COMMA := ,
> > +ifneq ($(EARLY_PRINTK_$(CONFIG_EARLY_PRINTK)),)
> > +EARLY_PRINTK_CFG := $(subst $(COMMA), ,$(EARLY_PRINTK_$(CONFIG_EARLY_PRINTK)))
> > +else
> > +EARLY_PRINTK_CFG := $(subst $(COMMA), ,$(CONFIG_EARLY_PRINTK))
> > +endif
> 
> If you're respinning this, it might be neater as
> 
> CONFIG_EARLY_PRINTK := $(or $(EARLY_PRINTK_$(CONFIG_EARLY_PRINTK)), $(CONFIG_EARLY_PRINTK)
> EARLY_PRINTK_CFG := $(subst $(COMMA), ,$(CONFIG_EARLY_PRINTK))

I didn't know about $(or ...) (but I suppose I could have guessed it
existed, I wonder since when though).

In my early testing I found that 
	CONFIG_EARLY_PRINTK := $(EARLY_PRINTK_$(CONFIG_EARLY_PRINTK))
didn't do as I expected with CONFIG_EARLY_PRINTK on the make command
line, but it's possible I messed up the trial.

> Or maybe not, now that I've written it out. :) Either way is probably fine.

:-)

I could do:

EARLY_PRINTK_CFG := $(subst $(COMMA), ,$(or $(EARLY_PRINTK_$(CONFIG_EARLY_PRINTK)),
                                            $(CONFIG_EARLY_PRINTK)))

Not sure that's better either.

Ian.