netdev - Re: [PATCH] net: tulip: turn compile-time warning into dev

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Message-ID: <20151119122610.GF22786@arm.com>
Date:	Thu, 19 Nov 2015 12:26:10 +0000
From:	Will Deacon <will.deacon@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
	ard.biesheuvel@...aro.org,
	Grant Grundler <grundler@...isc-linux.org>
Subject: Re: [PATCH] net: tulip: turn compile-time warning into dev_warn()

On Thu, Nov 19, 2015 at 11:42:26AM +0100, Arnd Bergmann wrote:
> The tulip driver causes annoying build-time warnings for allmodconfig
> builds for all recent architectures:
> 
> dec/tulip/winbond-840.c:910:2: warning: #warning Processor architecture undefined
> dec/tulip/tulip_core.c:101:2: warning: #warning Processor architecture undefined!
> 
> This is the last remaining warning for arm64, and I'd like to get rid of
> it. We don't really know the cache line size, architecturally it would
> be at least 16 bytes, but all implementations I found have 64 or 128
> bytes. Configuring tulip for 32-byte lines as we do on ARM32 seems to
> be the safe but slow default, and nobody who cares about performance these
> days would use a tulip chip anyway, so we can just use that.
> 
> To save the next person the job of trying to find out what this is for
> and picking a default for their architecture just to kill off the warning,
> I'm now removing the preprocessor #warning and turning it into a pr_warn
> or dev_warn that prints the equivalent information when the driver gets
> loaded.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> diff --git a/drivers/net/ethernet/dec/tulip/tulip_core.c b/drivers/net/ethernet/dec/tulip/tulip_core.c
> index ed41559bae77..b553409e04ad 100644
> --- a/drivers/net/ethernet/dec/tulip/tulip_core.c
> +++ b/drivers/net/ethernet/dec/tulip/tulip_core.c
> @@ -98,8 +98,7 @@ static int csr0 = 0x01A00000 | 0x4800;
>  #elif defined(__mips__)
>  static int csr0 = 0x00200000 | 0x4000;
>  #else
> -#warning Processor architecture undefined!
> -static int csr0 = 0x00A00000 | 0x4800;
> +static int csr0;
>  #endif
>  
>  /* Operational parameters that usually are not changed. */
> @@ -1982,6 +1981,12 @@ static int __init tulip_init (void)
>  	pr_info("%s", version);
>  #endif
>  
> +	if (!csr0) {
> +		pr_warn("tulip: unknown CPU architecture, using default csr0\n");
> +		/* default to 8 longword cache line alignment */
> +		csr0 = 0x00A00000 | 0x4800;

Maybe print "defaulting to 8 longword cache line alignment" instead of
"default csr0"?

> diff --git a/drivers/net/ethernet/dec/tulip/winbond-840.c b/drivers/net/ethernet/dec/tulip/winbond-840.c
> index 9beb3d34d4ba..3c0e4d5c5fef 100644
> --- a/drivers/net/ethernet/dec/tulip/winbond-840.c
> +++ b/drivers/net/ethernet/dec/tulip/winbond-840.c
> @@ -907,7 +907,7 @@ static void init_registers(struct net_device *dev)
>  #elif defined(CONFIG_SPARC) || defined (CONFIG_PARISC) || defined(CONFIG_ARM)
>  	i |= 0x4800;
>  #else
> -#warning Processor architecture undefined
> +	dev_warn(&dev->dev, "unknown CPU architecture, using default csr0 setting\n");
>  	i |= 0x4800;

Then we could print the default csr0 value here.

But, to be honest, this patch fixes a #warning on arm64 for a driver that
I never expect to be used. So whatever you do to silence it:

  Acked-by: Will Deacon <will.deacon@....com>

/me waits for on-soc tulip integration.

Will
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