ddc.c revision 1.6 
1/* $NetBSD: ddc.c,v 1.6 2015/07/25 15:20:49 jmcneill Exp $ */
2
3/*-
4 * Copyright (c) 2006 Itronix Inc.
5 * All rights reserved.
6 *
7 * Written by Garrett D'Amore for Itronix Inc.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. The name of Itronix Inc. may not be used to endorse
18 *    or promote products derived from this software without specific
19 *    prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY ITRONIX INC. ``AS IS'' AND ANY EXPRESS
22 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
23 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL ITRONIX INC. BE LIABLE FOR ANY
25 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
27 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
28 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
29 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
30 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
31 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34#include <sys/cdefs.h>
35__KERNEL_RCSID(0, "$NetBSD: ddc.c,v 1.6 2015/07/25 15:20:49 jmcneill Exp $");
36
37#include <sys/param.h>
38#include <sys/systm.h>
39#include <sys/device.h>
40#include <sys/kernel.h>
41
42#include <sys/bus.h>
43#include <dev/i2c/i2cvar.h>
44#include <dev/i2c/ddcreg.h>
45#include <dev/i2c/ddcvar.h>
46
47/*
48 * VESA Display Data Channel I2C client, used to access EDID
49 * information.
50 *
51 * Note that this only supports DDC version 2, which uses normal I2C.
52 * The older DDCv1 standard used sync signaling to provide the I2C
53 * clock, and is typically not used on reasonably recent monitors.
54 */
55
56struct ddc_softc {
57	i2c_tag_t	sc_tag;
58	int		sc_address;
59};
60
61static int ddc_match(device_t, cfdata_t, void *);
62static void ddc_attach(device_t, device_t, void *);
63
64CFATTACH_DECL_NEW(ddc, sizeof (struct ddc_softc),
65    ddc_match, ddc_attach, NULL, NULL);
66
67static int
68ddc_match(device_t parent, cfdata_t cf, void *aux)
69{
70	struct i2c_attach_args *ia = aux;
71
72	if (ia->ia_addr == DDC_ADDR)
73		return 1;
74	return 0;
75}
76
77static void
78ddc_attach(device_t parent, device_t self, void *aux)
79{
80	struct ddc_softc *sc = device_private(self);
81	struct i2c_attach_args *ia = aux;
82
83	sc->sc_tag = ia->ia_tag;
84	sc->sc_address = ia->ia_addr;
85
86	aprint_naive(": DDC\n");
87	aprint_normal(": DDC\n");
88}
89
90/* XXX: add cdev ops? */
91
92int
93ddc_read_edid(i2c_tag_t tag, uint8_t *dest, size_t len)
94{
95	return ddc_read_edid_block(tag, dest, len, DDC_EDID_START);
96}
97
98int
99ddc_read_edid_block(i2c_tag_t tag, uint8_t *dest, size_t len, uint8_t block)
100{
101	uint8_t edid[256];
102	uint8_t wbuf[2];
103	int error;
104
105	if ((error = iic_acquire_bus(tag, I2C_F_POLL)) != 0)
106		return error;
107
108	wbuf[0] = block >> 1;	/* start address */
109
110	if ((error = iic_exec(tag, I2C_OP_READ_WITH_STOP, DDC_ADDR, wbuf, 1,
111		edid, sizeof(edid), I2C_F_POLL)) != 0) {
112		iic_release_bus(tag, I2C_F_POLL);
113		return error;
114	}
115	iic_release_bus(tag, I2C_F_POLL);
116
117	if (block & 1) {
118		memcpy(dest, &edid[128], min(len, 128));
119	} else {
120		memcpy(dest, &edid[0], min(len, 128));
121	}
122
123	return 0;
124}
125
126int
127ddc_dev_read_edid(device_t dev, uint8_t *dest, size_t len)
128{
129	return ddc_dev_read_edid_block(dev, dest, len, DDC_EDID_START);
130}
131
132int
133ddc_dev_read_edid_block(device_t dev, uint8_t *dest, size_t len, uint8_t block)
134{
135	if (!device_is_a(dev, "ddc"))
136		return EINVAL;
137
138	const struct ddc_softc *sc = device_private(dev);
139	return ddc_read_edid_block(sc->sc_tag, dest, len, block);
140}
141