Re: [PATCH 02/14] can: rx-fifo: Increase MB size limit from 32 to 64

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 11/06/2014 05:03 PM, David Jander wrote:
> On Thu, 06 Nov 2014 09:41:59 +0100
> Marc Kleine-Budde <mkl@pengutronix.de> wrote:
> 
>> On 11/06/2014 09:34 AM, David Jander wrote:
>>> Signed-off-by: David Jander <david@protonic.nl>
>>> ---
>>>  drivers/net/can/dev.c   | 24 ++++++++++++------------
>>>  include/linux/can/dev.h | 12 ++++++------
>>>  2 files changed, 18 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
>>> index c1e53e9..930b9f4 100644
>>> --- a/drivers/net/can/dev.c
>>> +++ b/drivers/net/can/dev.c
>>> @@ -289,20 +289,20 @@ static unsigned int can_rx_fifo_inc(struct
>>> can_rx_fifo *fifo, unsigned int *val) return (*val)--;
>>>  }
>>>  
>>> -static u32 can_rx_fifo_mask_low(struct can_rx_fifo *fifo)
>>> +static u64 can_rx_fifo_mask_low(struct can_rx_fifo *fifo)
>>>  {
>>>  	if (fifo->inc)
>>> -		return ~0U >> (32 + fifo->low_first - fifo->high_first)
>>> << fifo->low_first;
>>> +		return ~0LLU >> (64 + fifo->low_first - fifo->high_first)
>>> << fifo->low_first; else
>>> -		return ~0U >> (32 - fifo->low_first + fifo->high_first)
>>> << (fifo->high_first + 1);
>>> +		return ~0LLU >> (64 - fifo->low_first + fifo->high_first)
>>> << (fifo->high_first + 1);
>>
>> Yesterday I stumbled over GENMASK_ULL
>> http://lxr.free-electrons.com/source/include/linux/bitops.h#L22
>> Does it make sense to use it here?
> 
> Looks like its exactly what is needed here.... nice.
> 
> Btw, there is a subtle bug in the line you linked to:
> 
>> #define GENMASK_ULL(h, l)       (((U64_C(1) << ((h) - (l) + 1)) - 1) << (l))
> 
> The _ULL in the name of the macro seems to hint to "unsigned long long", while
> the implementation seems to assume that it means U64_C. This is obviously
> wrong, although for most platforms that are currently capable of running
> Linux, those are probably equivalent...

#define U64_C(x) x ## ULL

Marc

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