Re: [PATCH v4 07/18] nvme: Fix reservation status related structs

[Mike Christie <michael.christie@xxxxxxxxxx>]

On 3/14/23 12:15 PM, Christoph Hellwig wrote:
> On Fri, Feb 24, 2023 at 11:44:51AM -0600, Mike Christie wrote:
>> +	__u8	resv10[14];
>> +	union {
>> +		struct {
>> +			__u8	rsvd24[40];
>> +			struct nvme_registered_ctrl_ext regctl_eds[0];
>> +		};
>> +		struct nvme_registered_ctrl regctl_ds[0];
>> +	};
> 
> ... actually - I think both these zero sized arrays should
> be the modern [] notation.

gcc at least doesn't let you use [] on a member in a union. You get:

./include/linux/nvme.h:804:31: error: flexible array member in union
  804 |   struct nvme_registered_ctrl regctl_ds[];


We could do separate structs though:


struct nvme_registered_ctrl {
	__le16	cntlid;
	__u8	rcsts;
	__u8	rsvd3[5];
	__le64	hostid;
	__le64	rkey;
};

struct nvme_reservation_status {
	__le32	gen;
	__u8	rtype;
	__u8	regctl[2];
	__u8	resv5[2];
	__u8	ptpls;
	__u8	resv10[14];
	struct nvme_registered_ctrl regctl_ds[];
};

struct nvme_registered_ctrl_ext {
	__le16	cntlid;
	__u8	rcsts;
	__u8	rsvd3[5];
	__le64	rkey;
	__u8	hostid[16];
	__u8	rsvd32[32];
};

struct nvme_reservation_status_ext {
	__le32	gen;
	__u8	rtype;
	__u8	regctl[2];
	__u8	resv5[2];
	__u8	ptpls;
	__u8	resv10[14];
	__u8	rsvd24[40];
	struct nvme_registered_ctrl_ext regctl_eds[];
};