linux-kernel - Re: [PATCH 5/6] sparc32: Do not select GENERIC_ISA

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Date: Sat, 24 Feb 2024 05:29:43 +0000 (GMT)
From: "Maciej W. Rozycki" <macro@...am.me.uk>
To: Sam Ravnborg <sam@...nborg.org>
cc: Miquel Raynal <miquel.raynal@...tlin.com>, sparclinux@...r.kernel.org, 
    linux-parport@...ts.infradead.org, "David S. Miller" <davem@...emloft.net>, 
    Andreas Larsson <andreas@...sler.com>, 
    Randy Dunlap <rdunlap@...radead.org>, Arnd Bergmann <arnd@...db.de>, 
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] sparc32: Do not select GENERIC_ISA_DMA

On Sat, 24 Feb 2024, Maciej W. Rozycki wrote:

> > sparc32 do not support generic isa dma, so do not select the symbol.
> > Without this fix, the following patch would break the build with a
> > missing prototype.
> 
>  Not according to my observations, kernel/dma.c is always built for 
> GENERIC_ISA_DMA configurations, so:
> 
> kernel/dma.c:70:5: error: no previous prototype for 'request_dma' [-Werror=missing-prototypes]
>    70 | int request_dma(unsigned int dmanr, const char * device_id)
>       |     ^~~~~~~~~~~
> kernel/dma.c:88:6: error: no previous prototype for 'free_dma' [-Werror=missing-prototypes]
>    88 | void free_dma(unsigned int dmanr)
>       |      ^~~~~~~~
> 
> are issued regardless (and FAOD with PARPORT_PC unset).
> 
>  I can't speak for SPARC support for ISA DMA, but it seems to me like the 
> second sentence would best be removed, as would the Fixes: tag (in favour 
> to:
> 
> Fixes: 0fcb70851fbf ("Makefile.extrawarn: turn on missing-prototypes globally")
> 
> I presume), and possibly the messages quoted above included instead.

 Actually I think ZONE_DMA should go too (it's linked to GENERIC_ISA_DMA, 
isn't it? -- cf. commit 5ac6da669e24 ("[PATCH] Set CONFIG_ZONE_DMA for 
arches with GENERIC_ISA_DMA")), and the whole thing use:

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

The GENERIC_ISA_DMA option itself was added to arch/sparc/config.in with 
2.5.31 as:

define_bool CONFIG_GENERIC_ISA_DMA y

despite of:

define_bool CONFIG_ISA n

for a reason not clear to me (BLK_DEV_FD? -- but on SPARC that uses some 
hacks to work in the absence of ISA DMA anyway).

 Am I missing anything here?

  Maciej