Home | History | Annotate | Line # | Download | only in i2c
ddc.c revision 1.2 
      1 /* $NetBSD: ddc.c,v 1.2 2007/10/19 11:59:43 ad 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 1.2 2007/10/19 11:59:43 ad 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 	struct device	sc_dev;
     58 	i2c_tag_t	sc_tag;
     59 	int		sc_address;
     60 };
     61 
     62 static int ddc_match(struct device *, struct cfdata *, void *);
     63 static void ddc_attach(struct device *, struct device *, void *);
     64 
     65 CFATTACH_DECL(ddc, sizeof (struct ddc_softc),
     66     ddc_match, ddc_attach, NULL, NULL);
     67 
     68 static int
     69 ddc_match(struct device *parent, struct cfdata *cf, void *aux)
     70 {
     71 	struct i2c_attach_args *ia = aux;
     72 
     73 	if (ia->ia_addr == DDC_ADDR)
     74 		return 1;
     75 	return 0;
     76 }
     77 
     78 static void
     79 ddc_attach(struct device *parent, struct device *self, void *aux)
     80 {
     81 	struct ddc_softc *sc = device_private(self);
     82 	struct i2c_attach_args *ia = aux;
     83 
     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 
     92 int
     93 ddc_read_edid(i2c_tag_t tag, uint8_t *dest, size_t len)
     94 {
     95 	uint8_t		wbuf[2];
     96 
     97 	if (iic_acquire_bus(tag, I2C_F_POLL) != 0)
     98 		return -1;
     99 
    100 	wbuf[0] = DDC_EDID_START;	/* start address */
    101 
    102 	if (iic_exec(tag, I2C_OP_READ_WITH_STOP, DDC_ADDR, wbuf, 1, dest,
    103 		len, I2C_F_POLL)) {
    104 		iic_release_bus(tag, I2C_F_POLL);
    105 		return -1;
    106 	}
    107 	iic_release_bus(tag, I2C_F_POLL);
    108 	return 0;
    109 }
    110