[RFC 3/3] nvme : Add ioctl to query nvme attributes

[Keith Busch]

On Thu, Oct 27, 2022 at 05:57:24PM +0200, Joel Granados wrote:
> +{
> +	int ret;
> +	struct nvme_id_ctrl *id_ctrl;
> +	struct nvme_get_attr nvme_get_attr = {0};
> +	struct nvme_id_ctrl_nvm *id_ctrl_nvm;
> +	__u32 usize;
> +
> +	BUILD_BUG_ON(sizeof(struct nvme_get_attr) < NVME_IOCTL_GET_ATTR_V0SZ);
> +	BUILD_BUG_ON(sizeof(struct nvme_get_attr) != NVME_IOCTL_GET_ATTR_CURSZ);
> +
> +	if (copy_from_user(&nvme_get_attr, arg, 2 * sizeof(__u32)))
> +		return -EFAULT;
> +
> +	if (nvme_get_attr.flags != 0)
> +		return -EINVAL;
> +
> +	switch (nvme_get_attr.argsz) {
> +	case NVME_IOCTL_GET_ATTR_V0SZ:
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +	usize = nvme_get_attr.argsz;
> +
> +	ret = nvme_identify_ctrl(ctrl, &id_ctrl);
> +	if (ret)
> +		return ret;
> +
> +	ret = nvme_identify_cs_ctrl(ctrl, &id_ctrl_nvm);
> +	if (ret)
> +		return ret;
> +
> +	nvme_get_attr.argsz = NVME_IOCTL_GET_ATTR_CURSZ;
> +	nvme_get_attr.mpsmin = NVME_CAP_MPSMIN(ctrl->cap);
> +	nvme_get_attr.vsl = id_ctrl_nvm->vsl;
> +	nvme_get_attr.wzsl = id_ctrl_nvm->wzsl;
> +	nvme_get_attr.wusl = id_ctrl_nvm->wusl;
> +	nvme_get_attr.dmrl = id_ctrl_nvm->dmrl;
> +	nvme_get_attr.dmsl = id_ctrl_nvm->dmsl;
> +	nvme_get_attr.dmrsl = id_ctrl_nvm->dmrsl;
> +	nvme_get_attr.oncs = id_ctrl->oncs;
> +	nvme_get_attr.mdts = id_ctrl->mdts;

You already have the 'struct nvme_ctrl' that saves nearly all these
values. We shouldn't need to send new IO when you can just reference the
cached values instead.

> +struct nvme_get_attr {
> +	__u32	argsz;
> +	__u32	flags;
> +
> +	/*
> +	 * Memory Page Size MINimum : The host should not configure a page size that
> +	 * is larger than (2 ^ (12 + mpsmin)). Comes from [3]
> +	 */
> +	__u32	mpsmin;
> +
> +	/*
> +	 * Verify Size Limit : Recommended or supported data size for a verify
> +	 * command. From [2].
> +	 */
> +	__u8	vsl;
> +
> +	/*
> +	 * Write Zeroes Size Limit : Recommended or supported data size for a
> +	 * zeroes command. From [2].
> +	 */
> +	__u8	wzsl;
> +
> +	/*
> +	 * Write Uncorrected Size Limit : Recommended or supported data size for
> +	 * an uncorrected command. From [2].
> +	 */
> +	__u8	wusl;
> +
> +	/*
> +	 * Dataset Management Ranges Limit : Recommended or supported maximum
> +	 * number of logical block ranges for the Dataset Management Command.
> +	 * From [2].
> +	 */
> +	__u8	dmrl;
> +
> +	/*
> +	 * Dataset Management Size Limit : Recommended or supported maximum of
> +	 * total number of logical blocks for a Dataset Management Command.
> +	 * From [2].
> +	 */
> +	__le64	dmsl;
> +
> +	/*
> +	 * Dataset Management Range Size Limit : Recommended or supported maximum
> +	 * number of logical blocks in a range of a Dataset Management Command.
> +	 * From [2].
> +	 */
> +	__le32	dmrsl;
> +
> +	/*
> +	 * Optional NVM Command Support. Is needed to make sense of attributes
> +	 * like vsl, wzsl, wusl... Comes from [1].
> +	 */
> +	__le16	oncs;

Don't use the little-endian format for values that are not going over
the wire.