Re: [patch 10/11] drivers/scsi/: Use the DMA_{64,32}BIT_MASK constants

[Matthew Wilcox <matthew@wil.cx>]

On Mon, Mar 07, 2005 at 09:27:17AM -0500, Jes Sorensen wrote:
> Matthew> We've had drivers with typos.  Missing one f suddenly causes
> Matthew> all your memory to come from ZONE_DMA.  Having an extra f
> Matthew> causes your driver to work ... most of the time on machines
> Matthew> with >4GB ram.  Sure, your driver doesn't, but when looking
> Matthew> over a lot of drivers, it's easier if everyone's using the
> Matthew> same macros.
> 
> If these were the only two masks ever used I'd agree with you. However
> there's several other in use and more will probably be added, so we're
> going to end up with drivers sometimes using constants and other times
> hex values causing an even bigger mess ;-(

No, that's a *good thing*.  It let's you know the driver's doing something
non-standard.  Here's what sym2 looks like these days:

#if SYM_CONF_DMA_ADDRESSING_MODE > 0
#if   SYM_CONF_DMA_ADDRESSING_MODE == 1
#define DMA_DAC_MASK    0x000000ffffffffffULL /* 40-bit */
#elif SYM_CONF_DMA_ADDRESSING_MODE == 2
#define DMA_DAC_MASK    DMA_64BIT_MASK
#endif
        if ((np->features & FE_DAC) &&
                        !pci_set_dma_mask(np->s.device, DMA_DAC_MASK)) {
                np->use_dac = 1;
                return 0;
        }
#endif

        if (!pci_set_dma_mask(np->s.device, DMA_32BIT_MASK))
                return 0;

        printf_warning("%s: No suitable DMA available\n", sym_name(np));
        return -1;

I suspect that should be a dev_err rather than a printf_warning, but
my point stands; this is a *much* easier way of doing things.  You can
see exactly where we're doing standard things and where we're doing
weird things.

-- 
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