[PATCH] fbdev: Add generic ddc read functionality

Adds functionality to read the EDID information over the DDC bus in a generic
way.  This code is based on the DDC implementation in the radeon driver.

[adaplas]
- separate from fbmon.c and place in new file fb_ddc.c
- remove dependency to CONFIG_I2C and CONFIG_I2C_ALGOBIT, otherwise, feature
  will not compile if i2c support is compiled as a module
- feature is selectable only by drivers needing it. It must have a
  'select FB_DDC if xxx' in Kconfig
- change printk's to dev_*, the i2c people prefers it
Signed-off-by: Dennis Munsie <dmunsie@cecropia.com>
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/video/Kconfig

@@ -53,6 +53,11 @@ config FB
 	  (e.g. an accelerated X server) and that are not frame buffer
 	  device-aware may cause unexpected results. If unsure, say N.
 
+config FB_DDC
+       tristate
+       depends on FB && I2C && I2C_ALGOBIT
+       default n
+
 config FB_CFB_FILLRECT
 	tristate
 	depends on FB

drivers/video/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_FB_CFB_FILLRECT)  += cfbfillrect.o
 obj-$(CONFIG_FB_CFB_COPYAREA)  += cfbcopyarea.o
 obj-$(CONFIG_FB_CFB_IMAGEBLIT) += cfbimgblt.o
 obj-$(CONFIG_FB_MACMODES)      += macmodes.o
+obj-$(CONFIG_FB_DDC)           += fb_ddc.o
 
 # Hardware specific drivers go first
 obj-$(CONFIG_FB_RETINAZ3)         += retz3fb.o

drivers/video/fb_ddc.c

+/*
+ * driver/vide/fb_ddc.c - DDC/EDID read support.
+ *
+ *  Copyright (C) 2006 Dennis Munsie <dmunsie@cecropia.com>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/fb.h>
+#include <linux/i2c-algo-bit.h>
+
+#include "edid.h"
+
+#define DDC_ADDR	0x50
+
+static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter)
+{
+	unsigned char start = 0x0;
+	struct i2c_msg msgs[] = {
+		{
+			.addr	= DDC_ADDR,
+			.len	= 1,
+			.buf	= &start,
+		}, {
+			.addr	= DDC_ADDR,
+			.flags	= I2C_M_RD,
+			.len	= EDID_LENGTH,
+		}
+	};
+	unsigned char *buf;
+
+	buf = kmalloc(EDID_LENGTH, GFP_KERNEL);
+	if (!buf) {
+		dev_warn(&adapter->dev, "unable to allocate memory for EDID "
+			 "block.\n");
+		return NULL;
+	}
+	msgs[1].buf = buf;
+
+	if (i2c_transfer(adapter, msgs, 2) == 2)
+		return buf;
+
+	dev_warn(&adapter->dev, "unable to read EDID block.\n");
+	kfree(buf);
+	return NULL;
+}
+
+unsigned char *fb_ddc_read(struct i2c_adapter *adapter)
+{
+	struct i2c_algo_bit_data *algo_data = adapter->algo_data;
+	unsigned char *edid = NULL;
+	int i, j;
+
+	algo_data->setscl(algo_data->data, 1);
+	algo_data->setscl(algo_data->data, 0);
+
+	for (i = 0; i < 3; i++) {
+		/* For some old monitors we need the
+		 * following process to initialize/stop DDC
+		 */
+		algo_data->setsda(algo_data->data, 0);
+		msleep(13);
+
+		algo_data->setscl(algo_data->data, 1);
+		for (j = 0; j < 5; j++) {
+			msleep(10);
+			if (algo_data->getscl(algo_data->data))
+				break;
+		}
+		if (j == 5)
+			continue;
+
+		algo_data->setsda(algo_data->data, 0);
+		msleep(15);
+		algo_data->setscl(algo_data->data, 0);
+		msleep(15);
+		algo_data->setsda(algo_data->data, 1);
+		msleep(15);
+
+		/* Do the real work */
+		edid = fb_do_probe_ddc_edid(adapter);
+		algo_data->setsda(algo_data->data, 0);
+		algo_data->setscl(algo_data->data, 0);
+		msleep(15);
+
+		algo_data->setscl(algo_data->data, 1);
+		for (j = 0; j < 10; j++) {
+			msleep(10);
+			if (algo_data->getscl(algo_data->data))
+				break;
+		}
+
+		algo_data->setsda(algo_data->data, 1);
+		msleep(15);
+		algo_data->setscl(algo_data->data, 0);
+		if (edid)
+			break;
+	}
+	/* Release the DDC lines when done or the Apple Cinema HD display
+	 * will switch off
+	 */
+	algo_data->setsda(algo_data->data, 0);
+	algo_data->setscl(algo_data->data, 0);
+
+	return edid;
+}
+
+EXPORT_SYMBOL_GPL(fb_ddc_read);
+
+MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
+MODULE_DESCRIPTION("DDC/EDID reading support");
+MODULE_LICENSE("GPL");

include/linux/fb.h

@@ -2,6 +2,7 @@
 #define _LINUX_FB_H
 
 #include <asm/types.h>
+#include <linux/i2c.h>
 
 /* Definitions of frame buffers						*/
 
@@ -940,6 +941,7 @@ extern void fb_edid_to_monspecs(unsigned char *edid,
 				struct fb_monspecs *specs);
 extern void fb_destroy_modedb(struct fb_videomode *modedb);
 extern int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb);
+extern unsigned char *fb_ddc_read(struct i2c_adapter *adapter);
 
 /* drivers/video/modedb.c */
 #define VESA_MODEDB_SIZE 34