[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>

1 files changed, 116 insertions, 0 deletions

diff --git a/drivers/video/fb_ddc.c b/drivers/video/fb_ddc.c
new file mode 100644
index 000000000000..3aa6ebf68f17
--- /dev/null
+++ b/drivers/video/fb_ddc.c
@@ -0,0 +1,116 @@
+/*
+ * 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");