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127 lines
2.8 KiB
127 lines
2.8 KiB
/* |
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* drivers/video/fb_ddc.c - DDC/EDID read support. |
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* |
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* Copyright (C) 2006 Dennis Munsie <[email protected]> |
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* |
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* This file is subject to the terms and conditions of the GNU General Public |
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* License. See the file COPYING in the main directory of this archive |
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* for more details. |
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*/ |
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#include <linux/delay.h> |
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#include <linux/device.h> |
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#include <linux/module.h> |
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#include <linux/fb.h> |
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#include <linux/i2c-algo-bit.h> |
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#include <linux/slab.h> |
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#include "../edid.h" |
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#define DDC_ADDR 0x50 |
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static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter) |
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{ |
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unsigned char start = 0x0; |
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unsigned char *buf = kmalloc(EDID_LENGTH, GFP_KERNEL); |
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struct i2c_msg msgs[] = { |
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{ |
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.addr = DDC_ADDR, |
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.flags = 0, |
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.len = 1, |
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.buf = &start, |
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}, { |
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.addr = DDC_ADDR, |
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.flags = I2C_M_RD, |
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.len = EDID_LENGTH, |
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.buf = buf, |
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} |
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}; |
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if (!buf) { |
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dev_warn(&adapter->dev, "unable to allocate memory for EDID " |
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"block.\n"); |
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return NULL; |
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} |
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if (i2c_transfer(adapter, msgs, 2) == 2) |
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return buf; |
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dev_warn(&adapter->dev, "unable to read EDID block.\n"); |
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kfree(buf); |
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return NULL; |
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} |
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unsigned char *fb_ddc_read(struct i2c_adapter *adapter) |
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{ |
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struct i2c_algo_bit_data *algo_data = adapter->algo_data; |
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unsigned char *edid = NULL; |
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int i, j; |
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algo_data->setscl(algo_data->data, 1); |
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for (i = 0; i < 3; i++) { |
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/* For some old monitors we need the |
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* following process to initialize/stop DDC |
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*/ |
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algo_data->setsda(algo_data->data, 1); |
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msleep(13); |
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algo_data->setscl(algo_data->data, 1); |
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if (algo_data->getscl) { |
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for (j = 0; j < 5; j++) { |
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msleep(10); |
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if (algo_data->getscl(algo_data->data)) |
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break; |
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} |
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if (j == 5) |
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continue; |
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} else { |
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udelay(algo_data->udelay); |
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} |
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algo_data->setsda(algo_data->data, 0); |
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msleep(15); |
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algo_data->setscl(algo_data->data, 0); |
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msleep(15); |
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algo_data->setsda(algo_data->data, 1); |
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msleep(15); |
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/* Do the real work */ |
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edid = fb_do_probe_ddc_edid(adapter); |
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algo_data->setsda(algo_data->data, 0); |
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algo_data->setscl(algo_data->data, 0); |
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msleep(15); |
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algo_data->setscl(algo_data->data, 1); |
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if (algo_data->getscl) { |
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for (j = 0; j < 10; j++) { |
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msleep(10); |
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if (algo_data->getscl(algo_data->data)) |
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break; |
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} |
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} else { |
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udelay(algo_data->udelay); |
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} |
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algo_data->setsda(algo_data->data, 1); |
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msleep(15); |
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algo_data->setscl(algo_data->data, 0); |
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algo_data->setsda(algo_data->data, 0); |
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if (edid) |
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break; |
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} |
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/* Release the DDC lines when done or the Apple Cinema HD display |
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* will switch off |
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*/ |
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algo_data->setsda(algo_data->data, 1); |
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algo_data->setscl(algo_data->data, 1); |
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adapter->class |= I2C_CLASS_DDC; |
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return edid; |
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} |
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EXPORT_SYMBOL_GPL(fb_ddc_read); |
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MODULE_AUTHOR("Dennis Munsie <[email protected]>"); |
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MODULE_DESCRIPTION("DDC/EDID reading support"); |
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MODULE_LICENSE("GPL");
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