Re: [RFC PATCH 1/3] bsg: add bsg_uring_cmd uapi structure

[Bart Van Assche <bvanassche@acm.org>]

On 1/12/26 1:46 AM, Yang Xiuwei wrote:
> +struct bsg_uring_cmd {
> +	__u64 cdb_addr;
> +	__u8  cdb_len;
> +	__u8  protocol;		/* [i] protocol type (BSG_PROTOCOL_*) */
> +	__u8  subprotocol;	/* [i] subprotocol type (BSG_SUB_PROTOCOL_*) */
> +	__u8  reserved1;
> +	__u32 din_iovec_count;	/* [i] 0 -> flat din transfer else
> +				 * din_xferp points to array of iovec
> +				 */
> +	__u32 din_xfer_len;	/* [i] bytes to be transferred from device */
> +	__u64 din_xferp;	/* [i] data in buffer address or iovec array
> +				 * address
> +				 */
> +	__u32 dout_iovec_count;	/* [i] 0 -> flat dout transfer else
> +				 * dout_xferp points to array of iovec
> +				 */
> +	__u32 dout_xfer_len;	/* [i] bytes to be transferred to device */
> +	__u64 dout_xferp;	/* [i] data out buffer address or iovec array address */
> +	__u32 sense_len;
> +	__u64 sense_addr;
> +	__u32 timeout_ms;
> +	__u32 flags;		/* [i] bit mask (BSG_FLAG_*) - reserved for future use */
> +	__u8  reserved[16];	/* reserved for future extension */

BSG supports much more than only SCSI. The above seems to support SCSI
commands only.

> +} __packed;

Applying __packed to a data structure in its entirety is wrong because
it causes compilers to generate suboptimal code on architectures that do
not support unaligned 16-/32-/64-bit accesses.

Bart.