Re: [PATCH v2 iproute2-next 1/3] rdma: update rdma_netlink.h to get new driver attributes

[David Ahern <dsahern@gmail.com>]

On 5/15/18 1:47 PM, Doug Ledford wrote:
> On Tue, 2018-05-15 at 13:37 -0600, David Ahern wrote:
>> On 5/14/18 9:42 AM, Steve Wise wrote:
>>> diff --git a/rdma/include/uapi/rdma/rdma_netlink.h b/rdma/include/uapi/rdma/rdma_netlink.h
>>> index 60416ed..40be0d8 100644
>>> --- a/rdma/include/uapi/rdma/rdma_netlink.h
>>> +++ b/rdma/include/uapi/rdma/rdma_netlink.h
>>> @@ -249,10 +249,22 @@ enum rdma_nldev_command {
>>>  	RDMA_NLDEV_NUM_OPS
>>>  };
>>>  
>>> +enum {
>>> +	RDMA_NLDEV_ATTR_ENTRY_STRLEN = 16,
>>> +};
>>> +
>>> +enum rdma_nldev_print_type {
>>> +	RDMA_NLDEV_PRINT_TYPE_UNSPEC,
>>> +	RDMA_NLDEV_PRINT_TYPE_HEX,
>>> +};
>>> +
>>>  enum rdma_nldev_attr {
>>>  	/* don't change the order or add anything between, this is ABI! */
>>
>> I asked this before and did not get a response. As the comment above
>> states with an emphasis (!) ...
>>
>>>  	RDMA_NLDEV_ATTR_UNSPEC,
>>>  
>>> +	/* Pad attribute for 64b alignment */
>>> +	RDMA_NLDEV_ATTR_PAD = RDMA_NLDEV_ATTR_UNSPEC,
>>> +
>>
>> ... are you really adding new attributes in the middle?
> 
> Not really.  The new item is being explicitly set to the same value as
> the item above it.  It therefore becomes two entries with the same enum
> value.  The rest of the enum is all unchanged.

sure for the above, but not the ones below.

Before this patch, this program:
$ cat a.c
#include <uapi/rdma/rdma_netlink.h>
#include <stdio.h>

int main(void)
{
	printf("RDMA_NLDEV_ATTR_NDEV_INDEX = %d\n", RDMA_NLDEV_ATTR_NDEV_INDEX);

	return 0;
}

prints this:
$ ./a.out
RDMA_NLDEV_ATTR_NDEV_INDEX = 50

After this patch,
$ ./a.out
RDMA_NLDEV_ATTR_NDEV_INDEX = 58


> 
>>>  	/* Identifier for ib_device */
>>>  	RDMA_NLDEV_ATTR_DEV_INDEX,		/* u32 */
>>>  
>>> @@ -387,6 +399,20 @@ enum rdma_nldev_attr {
>>>  	RDMA_NLDEV_ATTR_RES_PD_ENTRY,		/* nested table */
>>>  	RDMA_NLDEV_ATTR_RES_LOCAL_DMA_LKEY,	/* u32 */
>>>  	RDMA_NLDEV_ATTR_RES_UNSAFE_GLOBAL_RKEY,	/* u32 */
>>> +	/*
>>> +	 * driver-specific attributes.
>>> +	 */
>>> +	RDMA_NLDEV_ATTR_DRIVER,			/* nested table */
>>> +	RDMA_NLDEV_ATTR_DRIVER_ENTRY,		/* nested table */
>>> +	RDMA_NLDEV_ATTR_DRIVER_STRING,		/* string */
>>> +	/*
>>> +	 * u8 values from enum rdma_nldev_print_type
>>> +	 */
>>> +	RDMA_NLDEV_ATTR_DRIVER_PRINT_TYPE,	/* u8 */
>>> +	RDMA_NLDEV_ATTR_DRIVER_S32,		/* s32 */
>>> +	RDMA_NLDEV_ATTR_DRIVER_U32,		/* u32 */
>>> +	RDMA_NLDEV_ATTR_DRIVER_S64,		/* s64 */
>>> +	RDMA_NLDEV_ATTR_DRIVER_U64,		/* u64 */
>>
>> and again here.
>>
>>>  
>>>  	/*
>>>  	 * Provides logical name and index of netdevice which is
>>>
>>
>> --
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>