WSL2-Linux-Kernel/include/rdma/ib_mad.h

/*
 * Copyright (c) 2004 Mellanox Technologies Ltd.  All rights reserved.
 * Copyright (c) 2004 Infinicon Corporation.  All rights reserved.
 * Copyright (c) 2004 Intel Corporation.  All rights reserved.
 * Copyright (c) 2004 Topspin Corporation.  All rights reserved.
 * Copyright (c) 2004 Voltaire Corporation.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * $Id: ib_mad.h 2775 2005-07-02 13:42:12Z halr $
 */

#if !defined( IB_MAD_H )
#define IB_MAD_H

#include <linux/pci.h>

#include <rdma/ib_verbs.h>

/* Management base version */
#define IB_MGMT_BASE_VERSION			1

/* Management classes */
#define IB_MGMT_CLASS_SUBN_LID_ROUTED		0x01
#define IB_MGMT_CLASS_SUBN_DIRECTED_ROUTE	0x81
#define IB_MGMT_CLASS_SUBN_ADM			0x03
#define IB_MGMT_CLASS_PERF_MGMT			0x04
#define IB_MGMT_CLASS_BM			0x05
#define IB_MGMT_CLASS_DEVICE_MGMT		0x06
#define IB_MGMT_CLASS_CM			0x07
#define IB_MGMT_CLASS_SNMP			0x08
#define IB_MGMT_CLASS_VENDOR_RANGE2_START	0x30
#define IB_MGMT_CLASS_VENDOR_RANGE2_END		0x4F

#define	IB_OPENIB_OUI				(0x001405)

/* Management methods */
#define IB_MGMT_METHOD_GET			0x01
#define IB_MGMT_METHOD_SET			0x02
#define IB_MGMT_METHOD_GET_RESP			0x81
#define IB_MGMT_METHOD_SEND			0x03
#define IB_MGMT_METHOD_TRAP			0x05
#define IB_MGMT_METHOD_REPORT			0x06
#define IB_MGMT_METHOD_REPORT_RESP		0x86
#define IB_MGMT_METHOD_TRAP_REPRESS		0x07

#define IB_MGMT_METHOD_RESP			0x80

#define IB_MGMT_MAX_METHODS			128

/* RMPP information */
#define IB_MGMT_RMPP_VERSION			1

#define IB_MGMT_RMPP_TYPE_DATA			1
#define IB_MGMT_RMPP_TYPE_ACK			2
#define IB_MGMT_RMPP_TYPE_STOP			3
#define IB_MGMT_RMPP_TYPE_ABORT			4

#define IB_MGMT_RMPP_FLAG_ACTIVE		1
#define IB_MGMT_RMPP_FLAG_FIRST			(1<<1)
#define IB_MGMT_RMPP_FLAG_LAST			(1<<2)

#define IB_MGMT_RMPP_NO_RESPTIME		0x1F

#define	IB_MGMT_RMPP_STATUS_SUCCESS		0
#define	IB_MGMT_RMPP_STATUS_RESX		1
#define	IB_MGMT_RMPP_STATUS_ABORT_MIN		118
#define	IB_MGMT_RMPP_STATUS_T2L			118
#define	IB_MGMT_RMPP_STATUS_BAD_LEN		119
#define	IB_MGMT_RMPP_STATUS_BAD_SEG		120
#define	IB_MGMT_RMPP_STATUS_BADT		121
#define	IB_MGMT_RMPP_STATUS_W2S			122
#define	IB_MGMT_RMPP_STATUS_S2B			123
#define	IB_MGMT_RMPP_STATUS_BAD_STATUS		124
#define	IB_MGMT_RMPP_STATUS_UNV			125
#define	IB_MGMT_RMPP_STATUS_TMR			126
#define	IB_MGMT_RMPP_STATUS_UNSPEC		127
#define	IB_MGMT_RMPP_STATUS_ABORT_MAX		127

#define IB_QP0		0
#define IB_QP1		__constant_htonl(1)
#define IB_QP1_QKEY	0x80010000
#define IB_QP_SET_QKEY	0x80000000

enum {
	IB_MGMT_MAD_DATA = 232,
	IB_MGMT_RMPP_DATA = 220,
	IB_MGMT_VENDOR_DATA = 216,
	IB_MGMT_SA_DATA = 200
};

struct ib_mad_hdr {
	u8	base_version;
	u8	mgmt_class;
	u8	class_version;
	u8	method;
	__be16	status;
	__be16	class_specific;
	__be64	tid;
	__be16	attr_id;
	__be16	resv;
	__be32	attr_mod;
};

struct ib_rmpp_hdr {
	u8	rmpp_version;
	u8	rmpp_type;
	u8	rmpp_rtime_flags;
	u8	rmpp_status;
	__be32	seg_num;
	__be32	paylen_newwin;
};

typedef u64 __bitwise ib_sa_comp_mask;

#define IB_SA_COMP_MASK(n) ((__force ib_sa_comp_mask) cpu_to_be64(1ull << n))

/*
 * ib_sa_hdr and ib_sa_mad structures must be packed because they have
 * 64-bit fields that are only 32-bit aligned. 64-bit architectures will
 * lay them out wrong otherwise.  (And unfortunately they are sent on
 * the wire so we can't change the layout)
 */
struct ib_sa_hdr {
	__be64			sm_key;
	__be16			attr_offset;
	__be16			reserved;
	ib_sa_comp_mask		comp_mask;
} __attribute__ ((packed));

struct ib_mad {
	struct ib_mad_hdr	mad_hdr;
	u8			data[IB_MGMT_MAD_DATA];
};

struct ib_rmpp_mad {
	struct ib_mad_hdr	mad_hdr;
	struct ib_rmpp_hdr	rmpp_hdr;
	u8			data[IB_MGMT_RMPP_DATA];
};

struct ib_sa_mad {
	struct ib_mad_hdr	mad_hdr;
	struct ib_rmpp_hdr	rmpp_hdr;
	struct ib_sa_hdr	sa_hdr;
	u8			data[IB_MGMT_SA_DATA];
} __attribute__ ((packed));

struct ib_vendor_mad {
	struct ib_mad_hdr	mad_hdr;
	struct ib_rmpp_hdr	rmpp_hdr;
	u8			reserved;
	u8			oui[3];
	u8			data[IB_MGMT_VENDOR_DATA];
};

struct ib_class_port_info
{
	u8			base_version;
	u8			class_version;
	__be16			capability_mask;
	u8			reserved[3];
	u8			resp_time_value;
	u8			redirect_gid[16];
	__be32			redirect_tcslfl;
	__be16			redirect_lid;
	__be16			redirect_pkey;
	__be32			redirect_qp;
	__be32			redirect_qkey;
	u8			trap_gid[16];
	__be32			trap_tcslfl;
	__be16			trap_lid;
	__be16			trap_pkey;
	__be32			trap_hlqp;
	__be32			trap_qkey;
};

/**
 * ib_mad_send_buf - MAD data buffer and work request for sends.
 * @mad: References an allocated MAD data buffer.  The size of the data
 *   buffer is specified in the @send_wr.length field.
 * @mapping: DMA mapping information.
 * @mad_agent: MAD agent that allocated the buffer.
 * @context: User-controlled context fields.
 * @send_wr: An initialized work request structure used when sending the MAD.
 *   The wr_id field of the work request is initialized to reference this
 *   data structure.
 * @sge: A scatter-gather list referenced by the work request.
 *
 * Users are responsible for initializing the MAD buffer itself, with the
 * exception of specifying the payload length field in any RMPP MAD.
 */
struct ib_mad_send_buf {
	struct ib_mad		*mad;
	DECLARE_PCI_UNMAP_ADDR(mapping)
	struct ib_mad_agent	*mad_agent;
	void			*context[2];
	struct ib_send_wr	send_wr;
	struct ib_sge		sge;
};

/**
 * ib_get_rmpp_resptime - Returns the RMPP response time.
 * @rmpp_hdr: An RMPP header.
 */
static inline u8 ib_get_rmpp_resptime(struct ib_rmpp_hdr *rmpp_hdr)
{
	return rmpp_hdr->rmpp_rtime_flags >> 3;
}

/**
 * ib_get_rmpp_flags - Returns the RMPP flags.
 * @rmpp_hdr: An RMPP header.
 */
static inline u8 ib_get_rmpp_flags(struct ib_rmpp_hdr *rmpp_hdr)
{
	return rmpp_hdr->rmpp_rtime_flags & 0x7;
}

/**
 * ib_set_rmpp_resptime - Sets the response time in an RMPP header.
 * @rmpp_hdr: An RMPP header.
 * @rtime: The response time to set.
 */
static inline void ib_set_rmpp_resptime(struct ib_rmpp_hdr *rmpp_hdr, u8 rtime)
{
	rmpp_hdr->rmpp_rtime_flags = ib_get_rmpp_flags(rmpp_hdr) | (rtime << 3);
}

/**
 * ib_set_rmpp_flags - Sets the flags in an RMPP header.
 * @rmpp_hdr: An RMPP header.
 * @flags: The flags to set.
 */
static inline void ib_set_rmpp_flags(struct ib_rmpp_hdr *rmpp_hdr, u8 flags)
{
	rmpp_hdr->rmpp_rtime_flags = (rmpp_hdr->rmpp_rtime_flags & 0xF1) |
				     (flags & 0x7);
}

struct ib_mad_agent;
struct ib_mad_send_wc;
struct ib_mad_recv_wc;

/**
 * ib_mad_send_handler - callback handler for a sent MAD.
 * @mad_agent: MAD agent that sent the MAD.
 * @mad_send_wc: Send work completion information on the sent MAD.
 */
typedef void (*ib_mad_send_handler)(struct ib_mad_agent *mad_agent,
				    struct ib_mad_send_wc *mad_send_wc);

/**
 * ib_mad_snoop_handler - Callback handler for snooping sent MADs.
 * @mad_agent: MAD agent that snooped the MAD.
 * @send_wr: Work request information on the sent MAD.
 * @mad_send_wc: Work completion information on the sent MAD.  Valid
 *   only for snooping that occurs on a send completion.
 *
 * Clients snooping MADs should not modify data referenced by the @send_wr
 * or @mad_send_wc.
 */
typedef void (*ib_mad_snoop_handler)(struct ib_mad_agent *mad_agent,
				     struct ib_send_wr *send_wr,
				     struct ib_mad_send_wc *mad_send_wc);

/**
 * ib_mad_recv_handler - callback handler for a received MAD.
 * @mad_agent: MAD agent requesting the received MAD.
 * @mad_recv_wc: Received work completion information on the received MAD.
 *
 * MADs received in response to a send request operation will be handed to
 * the user after the send operation completes.  All data buffers given
 * to registered agents through this routine are owned by the receiving
 * client, except for snooping agents.  Clients snooping MADs should not
 * modify the data referenced by @mad_recv_wc.
 */
typedef void (*ib_mad_recv_handler)(struct ib_mad_agent *mad_agent,
				    struct ib_mad_recv_wc *mad_recv_wc);

/**
 * ib_mad_agent - Used to track MAD registration with the access layer.
 * @device: Reference to device registration is on.
 * @qp: Reference to QP used for sending and receiving MADs.
 * @mr: Memory region for system memory usable for DMA.
 * @recv_handler: Callback handler for a received MAD.
 * @send_handler: Callback handler for a sent MAD.
 * @snoop_handler: Callback handler for snooped sent MADs.
 * @context: User-specified context associated with this registration.
 * @hi_tid: Access layer assigned transaction ID for this client.
 *   Unsolicited MADs sent by this client will have the upper 32-bits
 *   of their TID set to this value.
 * @port_num: Port number on which QP is registered
 * @rmpp_version: If set, indicates the RMPP version used by this agent.
 */
struct ib_mad_agent {
	struct ib_device	*device;
	struct ib_qp		*qp;
	struct ib_mr		*mr;
	ib_mad_recv_handler	recv_handler;
	ib_mad_send_handler	send_handler;
	ib_mad_snoop_handler	snoop_handler;
	void			*context;
	u32			hi_tid;
	u8			port_num;
	u8			rmpp_version;
};

/**
 * ib_mad_send_wc - MAD send completion information.
 * @wr_id: Work request identifier associated with the send MAD request.
 * @status: Completion status.
 * @vendor_err: Optional vendor error information returned with a failed
 *   request.
 */
struct ib_mad_send_wc {
	u64			wr_id;
	enum ib_wc_status	status;
	u32			vendor_err;
};

/**
 * ib_mad_recv_buf - received MAD buffer information.
 * @list: Reference to next data buffer for a received RMPP MAD.
 * @grh: References a data buffer containing the global route header.
 *   The data refereced by this buffer is only valid if the GRH is
 *   valid.
 * @mad: References the start of the received MAD.
 */
struct ib_mad_recv_buf {
	struct list_head	list;
	struct ib_grh		*grh;
	struct ib_mad		*mad;
};

/**
 * ib_mad_recv_wc - received MAD information.
 * @wc: Completion information for the received data.
 * @recv_buf: Specifies the location of the received data buffer(s).
 * @rmpp_list: Specifies a list of RMPP reassembled received MAD buffers.
 * @mad_len: The length of the received MAD, without duplicated headers.
 *
 * For received response, the wr_id field of the wc is set to the wr_id
 *   for the corresponding send request.
 */
struct ib_mad_recv_wc {
	struct ib_wc		*wc;
	struct ib_mad_recv_buf	recv_buf;
	struct list_head	rmpp_list;
	int			mad_len;
};

/**
 * ib_mad_reg_req - MAD registration request
 * @mgmt_class: Indicates which management class of MADs should be receive
 *   by the caller.  This field is only required if the user wishes to
 *   receive unsolicited MADs, otherwise it should be 0.
 * @mgmt_class_version: Indicates which version of MADs for the given
 *   management class to receive.
 * @oui: Indicates IEEE OUI when mgmt_class is a vendor class
 *   in the range from 0x30 to 0x4f. Otherwise not used.
 * @method_mask: The caller will receive unsolicited MADs for any method
 *   where @method_mask = 1.
 */
struct ib_mad_reg_req {
	u8	mgmt_class;
	u8	mgmt_class_version;
	u8	oui[3];
	DECLARE_BITMAP(method_mask, IB_MGMT_MAX_METHODS);
};

/**
 * ib_register_mad_agent - Register to send/receive MADs.
 * @device: The device to register with.
 * @port_num: The port on the specified device to use.
 * @qp_type: Specifies which QP to access.  Must be either
 *   IB_QPT_SMI or IB_QPT_GSI.
 * @mad_reg_req: Specifies which unsolicited MADs should be received
 *   by the caller.  This parameter may be NULL if the caller only
 *   wishes to receive solicited responses.
 * @rmpp_version: If set, indicates that the client will send
 *   and receive MADs that contain the RMPP header for the given version.
 *   If set to 0, indicates that RMPP is not used by this client.
 * @send_handler: The completion callback routine invoked after a send
 *   request has completed.
 * @recv_handler: The completion callback routine invoked for a received
 *   MAD.
 * @context: User specified context associated with the registration.
 */
struct ib_mad_agent *ib_register_mad_agent(struct ib_device *device,
					   u8 port_num,
					   enum ib_qp_type qp_type,
					   struct ib_mad_reg_req *mad_reg_req,
					   u8 rmpp_version,
					   ib_mad_send_handler send_handler,
					   ib_mad_recv_handler recv_handler,
					   void *context);

enum ib_mad_snoop_flags {
	/*IB_MAD_SNOOP_POSTED_SENDS	   = 1,*/
	/*IB_MAD_SNOOP_RMPP_SENDS	   = (1<<1),*/
	IB_MAD_SNOOP_SEND_COMPLETIONS	   = (1<<2),
	/*IB_MAD_SNOOP_RMPP_SEND_COMPLETIONS = (1<<3),*/
	IB_MAD_SNOOP_RECVS		   = (1<<4)
	/*IB_MAD_SNOOP_RMPP_RECVS	   = (1<<5),*/
	/*IB_MAD_SNOOP_REDIRECTED_QPS	   = (1<<6)*/
};

/**
 * ib_register_mad_snoop - Register to snoop sent and received MADs.
 * @device: The device to register with.
 * @port_num: The port on the specified device to use.
 * @qp_type: Specifies which QP traffic to snoop.  Must be either
 *   IB_QPT_SMI or IB_QPT_GSI.
 * @mad_snoop_flags: Specifies information where snooping occurs.
 * @send_handler: The callback routine invoked for a snooped send.
 * @recv_handler: The callback routine invoked for a snooped receive.
 * @context: User specified context associated with the registration.
 */
struct ib_mad_agent *ib_register_mad_snoop(struct ib_device *device,
					   u8 port_num,
					   enum ib_qp_type qp_type,
					   int mad_snoop_flags,
					   ib_mad_snoop_handler snoop_handler,
					   ib_mad_recv_handler recv_handler,
					   void *context);

/**
 * ib_unregister_mad_agent - Unregisters a client from using MAD services.
 * @mad_agent: Corresponding MAD registration request to deregister.
 *
 * After invoking this routine, MAD services are no longer usable by the
 * client on the associated QP.
 */
int ib_unregister_mad_agent(struct ib_mad_agent *mad_agent);

/**
 * ib_post_send_mad - Posts MAD(s) to the send queue of the QP associated
 *   with the registered client.
 * @mad_agent: Specifies the associated registration to post the send to.
 * @send_wr: Specifies the information needed to send the MAD(s).
 * @bad_send_wr: Specifies the MAD on which an error was encountered.
 *
 * Sent MADs are not guaranteed to complete in the order that they were posted.
 *
 * If the MAD requires RMPP, the data buffer should contain a single copy
 * of the common MAD, RMPP, and class specific headers, followed by the class
 * defined data.  If the class defined data would not divide evenly into
 * RMPP segments, then space must be allocated at the end of the referenced
 * buffer for any required padding.  To indicate the amount of class defined
 * data being transferred, the paylen_newwin field in the RMPP header should
 * be set to the size of the class specific header plus the amount of class
 * defined data being transferred.  The paylen_newwin field should be
 * specified in network-byte order.
 */
int ib_post_send_mad(struct ib_mad_agent *mad_agent,
		     struct ib_send_wr *send_wr,
		     struct ib_send_wr **bad_send_wr);

/**
 * ib_coalesce_recv_mad - Coalesces received MAD data into a single buffer.
 * @mad_recv_wc: Work completion information for a received MAD.
 * @buf: User-provided data buffer to receive the coalesced buffers.  The
 *   referenced buffer should be at least the size of the mad_len specified
 *   by @mad_recv_wc.
 *
 * This call copies a chain of received MAD segments into a single data buffer,
 * removing duplicated headers.
 */
void ib_coalesce_recv_mad(struct ib_mad_recv_wc *mad_recv_wc, void *buf);

/**
 * ib_free_recv_mad - Returns data buffers used to receive a MAD.
 * @mad_recv_wc: Work completion information for a received MAD.
 *
 * Clients receiving MADs through their ib_mad_recv_handler must call this
 * routine to return the work completion buffers to the access layer.
 */
void ib_free_recv_mad(struct ib_mad_recv_wc *mad_recv_wc);

/**
 * ib_cancel_mad - Cancels an outstanding send MAD operation.
 * @mad_agent: Specifies the registration associated with sent MAD.
 * @wr_id: Indicates the work request identifier of the MAD to cancel.
 *
 * MADs will be returned to the user through the corresponding
 * ib_mad_send_handler.
 */
void ib_cancel_mad(struct ib_mad_agent *mad_agent, u64 wr_id);

/**
 * ib_modify_mad - Modifies an outstanding send MAD operation.
 * @mad_agent: Specifies the registration associated with sent MAD.
 * @wr_id: Indicates the work request identifier of the MAD to modify.
 * @timeout_ms: New timeout value for sent MAD.
 *
 * This call will reset the timeout value for a sent MAD to the specified
 * value.
 */
int ib_modify_mad(struct ib_mad_agent *mad_agent, u64 wr_id, u32 timeout_ms);

/**
 * ib_redirect_mad_qp - Registers a QP for MAD services.
 * @qp: Reference to a QP that requires MAD services.
 * @rmpp_version: If set, indicates that the client will send
 *   and receive MADs that contain the RMPP header for the given version.
 *   If set to 0, indicates that RMPP is not used by this client.
 * @send_handler: The completion callback routine invoked after a send
 *   request has completed.
 * @recv_handler: The completion callback routine invoked for a received
 *   MAD.
 * @context: User specified context associated with the registration.
 *
 * Use of this call allows clients to use MAD services, such as RMPP,
 * on user-owned QPs.  After calling this routine, users may send
 * MADs on the specified QP by calling ib_mad_post_send.
 */
struct ib_mad_agent *ib_redirect_mad_qp(struct ib_qp *qp,
					u8 rmpp_version,
					ib_mad_send_handler send_handler,
					ib_mad_recv_handler recv_handler,
					void *context);

/**
 * ib_process_mad_wc - Processes a work completion associated with a
 *   MAD sent or received on a redirected QP.
 * @mad_agent: Specifies the registered MAD service using the redirected QP.
 * @wc: References a work completion associated with a sent or received
 *   MAD segment.
 *
 * This routine is used to complete or continue processing on a MAD request.
 * If the work completion is associated with a send operation, calling
 * this routine is required to continue an RMPP transfer or to wait for a
 * corresponding response, if it is a request.  If the work completion is
 * associated with a receive operation, calling this routine is required to
 * process an inbound or outbound RMPP transfer, or to match a response MAD
 * with its corresponding request.
 */
int ib_process_mad_wc(struct ib_mad_agent *mad_agent,
		      struct ib_wc *wc);

/**
 * ib_create_send_mad - Allocate and initialize a data buffer and work request
 *   for sending a MAD.
 * @mad_agent: Specifies the registered MAD service to associate with the MAD.
 * @remote_qpn: Specifies the QPN of the receiving node.
 * @pkey_index: Specifies which PKey the MAD will be sent using.  This field
 *   is valid only if the remote_qpn is QP 1.
 * @ah: References the address handle used to transfer to the remote node.
 * @rmpp_active: Indicates if the send will enable RMPP.
 * @hdr_len: Indicates the size of the data header of the MAD.  This length
 *   should include the common MAD header, RMPP header, plus any class
 *   specific header.
 * @data_len: Indicates the size of any user-transferred data.  The call will
 *   automatically adjust the allocated buffer size to account for any
 *   additional padding that may be necessary.
 * @gfp_mask: GFP mask used for the memory allocation.
 *
 * This is a helper routine that may be used to allocate a MAD.  Users are
 * not required to allocate outbound MADs using this call.  The returned
 * MAD send buffer will reference a data buffer usable for sending a MAD, along
 * with an initialized work request structure.  Users may modify the returned
 * MAD data buffer or work request before posting the send.
 *
 * The returned data buffer will be cleared.  Users are responsible for
 * initializing the common MAD and any class specific headers.  If @rmpp_active
 * is set, the RMPP header will be initialized for sending.
 */
struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
					    u32 remote_qpn, u16 pkey_index,
					    struct ib_ah *ah, int rmpp_active,
					    int hdr_len, int data_len,
					    gfp_t gfp_mask);

/**
 * ib_free_send_mad - Returns data buffers used to send a MAD.
 * @send_buf: Previously allocated send data buffer.
 */
void ib_free_send_mad(struct ib_mad_send_buf *send_buf);

#endif /* IB_MAD_H */