[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>
diff --git a/drivers/video/fb_ddc.c b/drivers/video/fb_ddc.c
new file mode 100644
index 0000000..3aa6ebf
--- /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");