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ddc.c revision 1.3 
      1 /* $NetBSD: ddc.c,v 1.3 2008/05/04 15:26:29 xtraeme 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 1.3 2008/05/04 15:26:29 xtraeme 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 
     56 struct ddc_softc {
     57 	i2c_tag_t	sc_tag;
     58 	int		sc_address;
     59 };
     60 
     61 static int ddc_match(device_t, cfdata_t, void *);
     62 static void ddc_attach(device_t, device_t, void *);
     63 
     64 CFATTACH_DECL_NEW(ddc, sizeof (struct ddc_softc),
     65     ddc_match, ddc_attach, NULL, NULL);
     66 
     67 static int
     68 ddc_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 
     77 static void
     78 ddc_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_address = ia->ia_addr;
     84 
     85 	aprint_naive(": DDC\n");
     86 	aprint_normal(": DDC\n");
     87 }
     88 
     89 /* XXX: add cdev ops? */
     90 
     91 int
     92 ddc_read_edid(i2c_tag_t tag, uint8_t *dest, size_t len)
     93 {
     94 	uint8_t		wbuf[2];
     95 
     96 	if (iic_acquire_bus(tag, I2C_F_POLL) != 0)
     97 		return -1;
     98 
     99 	wbuf[0] = DDC_EDID_START;	/* start address */
    100 
    101 	if (iic_exec(tag, I2C_OP_READ_WITH_STOP, DDC_ADDR, wbuf, 1, dest,
    102 		len, I2C_F_POLL)) {
    103 		iic_release_bus(tag, I2C_F_POLL);
    104 		return -1;
    105 	}
    106 	iic_release_bus(tag, I2C_F_POLL);
    107 	return 0;
    108 }
    109