On 08/03/2018 01:03 PM, Tony Battersby wrote:
> On 08/03/2018 12:22 PM, Matthew Wilcox wrote:
>> On Fri, Aug 03, 2018 at 06:59:20PM +0300, Andy Shevchenko wrote:
>>>>>> I'm pretty sure this was created in an order to avoid bad looking (and
>>>>>> in some cases frightening) "NULL device *" part.
>>> JFYI: git log --no-merges --grep 'NULL device \*'
>> I think those commits actually argue in favour of Tony's patch to remove
>> the special casing. Is it really useful to create dma pools with a NULL
>> device?
>>
>>
> dma_alloc_coherent() does appear to support a NULL dev, so it might make
> sense in theory. But I can't find any in-tree callers that actually
> pass a NULL dev to dma_pool_create(). So for one of the dreaded (NULL
> device *) messages to show up, it would take both a new caller that
> passes a NULL dev to dma_pool_create() and a bug to cause the message to
> be printed. Is that worth the special casing?
>
Out of curiosity, I just tried to create a dmapool with a NULL dev and
it crashed on this:
static inline int dev_to_node(struct device *dev)
{
return dev->numa_node;
}
struct dma_pool *dma_pool_create(const char *name, struct device *dev,
size_t size, size_t align, size_t boundary)
{
...
retval = kmalloc_node(sizeof(*retval), GFP_KERNEL, dev_to_node(dev));
...
}
So either it needs more special cases for supporting a NULL dev, or the
special cases can be removed since no one does that anyway.
