Re: coccinelle and bitmask arithmetic

walter harms
2013-01-30T08:21:35Z

Am 29.01.2013 19:03, schrieb Joe Perches:
> On Tue, 2013-01-29 at 18:49 +0100, Julia Lawall wrote:
>> How about the following (from today's linux-next). They appear to be
>> trying to do the same calculation, once with + and once with |.
>
> (cc'ing the original developer and Russell King)
>
> Likely the it8152_pci_platform_notify uses should use +
>
>> arch/arm/common/it8152.c
>>
>> int dma_set_coherent_mask(struct device *dev, u64 mask)
>> {
>> if (mask >= PHYS_OFFSET + SZ_64M - 1)
>> return 0;
>>
>> return -EIO;
>> }
>>

Great hit Joe :)

Sometimes i am really surprised what code can be found
in the kernal and it is still working.
Having no clue of the code i suspect somebody tries to
check is mask outside the range it should read
PHYS_OFFSET |( SZ_64M - 1)
maybe someone should tell them that
1+1=10 while 1|1=1
It does not seem to matter here (or ... ?)

really perplexed,

wh

>> static int it8152_pci_platform_notify(struct device *dev)
>> {
>> if (dev->bus == &pci_bus_type) {
>> if (dev->dma_mask)
>> *dev->dma_mask = (SZ_64M - 1) | PHYS_OFFSET;
>> dev->coherent_dma_mask = (SZ_64M - 1) | PHYS_OFFSET;
>> dmabounce_register_dev(dev, 2048, 4096, it8152_needs_bounce);
>> }
>> return 0;
>> }
>
>
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