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      1 /*	$NetBSD: vbox_hgsmi.c,v 1.2 2021/12/18 23:45:44 riastradh Exp $	*/
      2 
      3 // SPDX-License-Identifier: MIT
      4 /*
      5  * Copyright (C) 2017 Oracle Corporation
      6  * Authors: Hans de Goede <hdegoede (at) redhat.com>
      7  */
      8 
      9 #include <sys/cdefs.h>
     10 __KERNEL_RCSID(0, "$NetBSD: vbox_hgsmi.c,v 1.2 2021/12/18 23:45:44 riastradh Exp $");
     11 
     12 #include "vbox_drv.h"
     13 #include "vboxvideo_vbe.h"
     14 #include "hgsmi_defs.h"
     15 
     16 /* One-at-a-Time Hash from http://www.burtleburtle.net/bob/hash/doobs.html */
     17 static u32 hgsmi_hash_process(u32 hash, const u8 *data, int size)
     18 {
     19 	while (size--) {
     20 		hash += *data++;
     21 		hash += (hash << 10);
     22 		hash ^= (hash >> 6);
     23 	}
     24 
     25 	return hash;
     26 }
     27 
     28 static u32 hgsmi_hash_end(u32 hash)
     29 {
     30 	hash += (hash << 3);
     31 	hash ^= (hash >> 11);
     32 	hash += (hash << 15);
     33 
     34 	return hash;
     35 }
     36 
     37 /* Not really a checksum but that is the naming used in all vbox code */
     38 static u32 hgsmi_checksum(u32 offset,
     39 			  const struct hgsmi_buffer_header *header,
     40 			  const struct hgsmi_buffer_tail *tail)
     41 {
     42 	u32 checksum;
     43 
     44 	checksum = hgsmi_hash_process(0, (u8 *)&offset, sizeof(offset));
     45 	checksum = hgsmi_hash_process(checksum, (u8 *)header, sizeof(*header));
     46 	/* 4 -> Do not checksum the checksum itself */
     47 	checksum = hgsmi_hash_process(checksum, (u8 *)tail, 4);
     48 
     49 	return hgsmi_hash_end(checksum);
     50 }
     51 
     52 void *hgsmi_buffer_alloc(struct gen_pool *guest_pool, size_t size,
     53 			 u8 channel, u16 channel_info)
     54 {
     55 	struct hgsmi_buffer_header *h;
     56 	struct hgsmi_buffer_tail *t;
     57 	size_t total_size;
     58 	dma_addr_t offset;
     59 
     60 	total_size = size + sizeof(*h) + sizeof(*t);
     61 	h = gen_pool_dma_alloc(guest_pool, total_size, &offset);
     62 	if (!h)
     63 		return NULL;
     64 
     65 	t = (struct hgsmi_buffer_tail *)((u8 *)h + sizeof(*h) + size);
     66 
     67 	h->flags = HGSMI_BUFFER_HEADER_F_SEQ_SINGLE;
     68 	h->data_size = size;
     69 	h->channel = channel;
     70 	h->channel_info = channel_info;
     71 	memset(&h->u.header_data, 0, sizeof(h->u.header_data));
     72 
     73 	t->reserved = 0;
     74 	t->checksum = hgsmi_checksum(offset, h, t);
     75 
     76 	return (u8 *)h + sizeof(*h);
     77 }
     78 
     79 void hgsmi_buffer_free(struct gen_pool *guest_pool, void *buf)
     80 {
     81 	struct hgsmi_buffer_header *h =
     82 		(struct hgsmi_buffer_header *)((u8 *)buf - sizeof(*h));
     83 	size_t total_size = h->data_size + sizeof(*h) +
     84 					     sizeof(struct hgsmi_buffer_tail);
     85 
     86 	gen_pool_free(guest_pool, (unsigned long)h, total_size);
     87 }
     88 
     89 int hgsmi_buffer_submit(struct gen_pool *guest_pool, void *buf)
     90 {
     91 	phys_addr_t offset;
     92 
     93 	offset = gen_pool_virt_to_phys(guest_pool, (unsigned long)buf -
     94 				       sizeof(struct hgsmi_buffer_header));
     95 	outl(offset, VGA_PORT_HGSMI_GUEST);
     96 	/* Make the compiler aware that the host has changed memory. */
     97 	mb();
     98 
     99 	return 0;
    100 }
    101