Hello, On 6/11/2013 4:34 AM, Bjorn Helgaas wrote:
[+cc Marek] On Mon, Jun 3, 2013 at 6:44 AM, Michal Simek <michal.simek@xxxxxxxxxx> wrote: > Check that dma_ops are initialized correctly. > > Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx> > --- > Functions dma_mmap_attrs(), dma_get_sgtable_attrs() > already have this checking. > > --- > include/asm-generic/dma-mapping-common.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/include/asm-generic/dma-mapping-common.h b/include/asm-generic/dma-mapping-common.h > index de8bf89..d430cab 100644 > --- a/include/asm-generic/dma-mapping-common.h > +++ b/include/asm-generic/dma-mapping-common.h > @@ -16,6 +16,7 @@ static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr, > dma_addr_t addr; > > kmemcheck_mark_initialized(ptr, size); > + BUG_ON(!ops); Does this actually help anything? I expected that if "ops" is NULL, we would just oops anyway when we attempted to call "ops->map_page()" because we already trap null pointer dereferences. At least, when I tried leaving a pci_bus.ops pointer NULL, I got a nice panic and backtrace even without adding an explicit BUG_ON(). I cc'd Marek, who added the similar BUG_ON()s in dma_mmap_attrs() and dma_get_sgtable_attrs() with d2b7428eb0 and 64ccc9c033.
I think that I've copied it from dma_alloc_coherent() in microblaze. You are right that lack of this check will also trigger oops in ops==NULL case, but I think that adding explicit check in all functions, which use it, is a good idea. It serves as a kind of documentation and
emphasizes that missing ops is really an issue. Best regards -- Marek Szyprowski Samsung R&D Institute Poland -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
