linux-kernel - Re: [PATCH v8 01/25] scsi/atari_scsi: Don't select CONFIG

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Date:   Sat, 29 Dec 2018 12:06:03 +1100 (AEDT)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     LEROY Christophe <christophe.leroy@....fr>
cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-m68k@...ts.linux-m68k.org,
        Michael Schmitz <schmitzmic@...il.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v8 01/25] scsi/atari_scsi: Don't select CONFIG_NVRAM

On Fri, 28 Dec 2018, LEROY Christophe wrote:

> Finn Thain <fthain@...egraphics.com.au> a ?crit?:
> 
> > On powerpc, setting CONFIG_NVRAM=n builds a kernel with no NVRAM support.
> > Setting CONFIG_NVRAM=m enables the /dev/nvram misc device module without
> > enabling NVRAM support in drivers. Setting CONFIG_NVRAM=y enables the
> > misc device (built-in) and also enables NVRAM support in drivers.
> >
> > m68k shares the valkyriefb driver with powerpc, and since that driver uses
> > NVRAM, it is affected by CONFIG_ATARI_SCSI, because of the use of
> > "select NVRAM".
> >
> > Adopt the powerpc convention on m68k to avoid surprises.
> >
> > Signed-off-by: Finn Thain <fthain@...egraphics.com.au>
> > Tested-by: Christian T. Steigies <cts@...ian.org>
> > ---
> > This patch temporarily disables CONFIG_NVRAM on Atari, to prevent build
> > failures when bisecting the rest of this patch series. It gets enabled
> > again with the introduction of CONFIG_HAVE_ARCH_NVRAM_OPS, once the
> > nvram_* global functions have been moved to an ops struct.
> > ---
> >  drivers/char/Kconfig      | 5 +----
> >  drivers/scsi/Kconfig      | 6 +++---
> >  drivers/scsi/atari_scsi.c | 7 ++++---
> >  3 files changed, 8 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
> > index 9d03b2ff5df6..5b54595dfe30 100644
> > --- a/drivers/char/Kconfig
> > +++ b/drivers/char/Kconfig
> > @@ -236,7 +236,7 @@ source "drivers/char/hw_random/Kconfig"
> >
> >  config NVRAM
> >  	tristate "/dev/nvram support"
> > -	depends on ATARI || X86 || GENERIC_NVRAM
> > +	depends on X86 || GENERIC_NVRAM
> >  	---help---
> >  	  If you say Y here and create a character special file /dev/nvram
> >  	  with major number 10 and minor number 144 using mknod ("man mknod"),
> > @@ -254,9 +254,6 @@ config NVRAM
> >  	  should NEVER idly tamper with it. See Ralf Brown's interrupt list
> >  	  for a guide to the use of CMOS bytes by your BIOS.
> >
> > -	  On Atari machines, /dev/nvram is always configured and does not need
> > -	  to be selected.
> > -
> >  	  To compile this driver as a module, choose M here: the
> >  	  module will be called nvram.
> >
> > diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
> > index 640cd1b31a18..924eb69e7fc4 100644
> > --- a/drivers/scsi/Kconfig
> > +++ b/drivers/scsi/Kconfig
> > @@ -1381,14 +1381,14 @@ config ATARI_SCSI
> >  	tristate "Atari native SCSI support"
> >  	depends on ATARI && SCSI
> >  	select SCSI_SPI_ATTRS
> > -	select NVRAM
> >  	---help---
> >  	  If you have an Atari with built-in NCR5380 SCSI controller (TT,
> >  	  Falcon, ...) say Y to get it supported. Of course also, if you have
> >  	  a compatible SCSI controller (e.g. for Medusa).
> >
> > -	  To compile this driver as a module, choose M here: the
> > -	  module will be called atari_scsi.
> > +	  To compile this driver as a module, choose M here: the module will
> > +	  be called atari_scsi. If you also enable NVRAM support, the SCSI
> > +	  host's ID is taken from the setting in TT RTC NVRAM.
> >
> >  	  This driver supports both styles of NCR integration into the
> >  	  system: the TT style (separate DMA), and the Falcon style (via
> > diff --git a/drivers/scsi/atari_scsi.c b/drivers/scsi/atari_scsi.c
> > index 89f5154c40b6..99e5729d910d 100644
> > --- a/drivers/scsi/atari_scsi.c
> > +++ b/drivers/scsi/atari_scsi.c
> > @@ -755,9 +755,10 @@ static int __init atari_scsi_probe(struct  
> > platform_device *pdev)
> >  	if (ATARIHW_PRESENT(TT_SCSI) && setup_sg_tablesize >= 0)
> >  		atari_scsi_template.sg_tablesize = setup_sg_tablesize;
> >
> > -	if (setup_hostid >= 0) {
> > +	if (setup_hostid >= 0)
> >  		atari_scsi_template.this_id = setup_hostid & 7;
> > -	} else {
> > +#ifdef CONFIG_NVRAM
> > +	else
> 
> Such ifdefs should be avoided in C files.
> It would be better to use
> 
> } else if (IS_ENABLED(CONFIG_NVRAM)) {
> 

I don't like #ifdefs either. However, as the maintainer of this file, I am 
okay with this one.

The old #ifdef CONFIG_NVRAM conditional compilation convention that gets 
used here and under drivers/video/fbdev could probably be improved upon 
but I consider this to be out-of-scope for this series, which is 
complicated enough.

And as explained in the commit log, CONFIG_NVRAM=y and CONFIG_NVRAM=m are 
treaded differently by drivers. Therefore, IS_ENABLED would be incorrect.

-- 

> >  		/* Test if a host id is set in the NVRam */
> >  		if (ATARIHW_PRESENT(TT_CLK) && nvram_check_checksum()) {
> >  			unsigned char b = nvram_read_byte(16);
> > @@ -768,7 +769,7 @@ static int __init atari_scsi_probe(struct  
> > platform_device *pdev)
> >  			if (b & 0x80)
> >  				atari_scsi_template.this_id = b & 7;
> >  		}
> > -	}
> > +#endif
> >
> >  	/* If running on a Falcon and if there's TT-Ram (i.e., more than one
> >  	 * memory block, since there's always ST-Ram in a Falcon), then
> > --
> > 2.19.2
> 
> 
>