Got it. You did mention about typedef in email chain, but I understood as different way to achieve same.
I reviewed my code and found that most of the fields between driver-adapter doesn't need attribute. So far (a) removing packed and (b) BUILD_BUG_ON looks sufficient for current set of structures. Initial test suffice the need. Thanks. Parav > -----Original Message----- > From: Jason Gunthorpe [mailto:jguntho...@obsidianresearch.com] > Sent: Friday, March 23, 2012 10:24 PM > To: Pandit, Parav > Cc: david.lai...@aculab.com; rol...@purestorage.com; linux- > r...@vger.kernel.org; net...@vger.kernel.org > Subject: Re: [PATCH 2/9] ocrdma: Driver for Emulex OneConnect RDMA > adapter > > On Fri, Mar 23, 2012 at 07:03:37AM -0700, parav.pan...@emulex.com wrote: > > > > David is saying you will get a 12 byte struct and fieldb will be > > > unaligned. Since > > > 12 is aligned to 4 no padding is added. > > > > So I decided to experiment above example before implementing in > > driver. However I find structure of 16 bytes (instead of 12) with > > padding after fielda in below example. Am I missing some compiler > > option or syntax error in attribute? Sorry to ask this silly question. > > I tried __attribute__((__aligned__(4))); too based on usage in other > > kernel code. > > I got the syntax wrong for that specific case (it is a little unintuitive.. > IMHO, > capping the alignment of a container should cap the alignment of all > members, otherwise it is nonsense!): > > typedef uint64_t u64_unaligned_8 __attribute__((__aligned__(4))); > > struct foo { > uint32_t fielda; > u64_unaligned_8 fieldb; > }; > > struct foo2 { > uint32_t fielda; > uint64_t fieldb; > }; > > int main(int argc,const char *argv[]) > { > printf("sizeof(foo) = %zu, fieldb = %zu\n",sizeof(struct foo), > offsetof(struct foo,fieldb)); > printf("sizeof(foo2) = %zu, fieldb = %zu\n",sizeof(struct foo2), > offsetof(struct foo2,fieldb)); > return 0; > } > > sizeof(foo) = 12, fieldb = 4 > sizeof(foo2) = 16, fieldb = 8 > > gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3) > > Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
