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/*
* ddc-ci.c: DDC-CI utilities, Linux-only
*
* Copyright (c) 2015 - 2017, Přemysl Janouch <p.janouch@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
// Sources: ddcciv1r1.pdf, i2c-dev.c in Linux, ddccontrol source code,
// http://www.boichat.ch/nicolas/ddcci/specs.html was also helpful
#include <sys/ioctl.h>
#include <linux/i2c-dev.h>
#ifndef I2C_FUNC_I2C
// Fuck you, openSUSE, for fucking up the previous file, see e.g.
// https://github.com/solettaproject/soletta/commit/427f47f
#include <linux/i2c.h>
#endif
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static void
log_message_custom (void *user_data, const char *quote, const char *fmt,
va_list ap)
{
(void) user_data;
FILE *stream = stdout;
fprintf (stream, PROGRAM_NAME ": ");
fputs (quote, stream);
vfprintf (stream, fmt, ap);
fputs ("\n", stream);
}
static void
wait_ms (long ms)
{
struct timespec ts = { 0, ms * 1000 * 1000 };
nanosleep (&ts, NULL);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#define DDC_LENGTH_XOR 0x80
enum
{
DDC_ADDRESS_HOST = 0x50, ///< Bus master's base address
DDC_ADDRESS_DISPLAY = 0x6E ///< The display's base address
};
enum { I2C_WRITE, I2C_READ };
enum
{
DDC_GET_VCP_FEATURE = 0x01, ///< Request info about a feature
DDC_GET_VCP_FEATURE_REPLY = 0x02, ///< Feature info response
DDC_SET_VCP_FEATURE = 0x03 ///< Set or activate a feature
};
enum
{
VCP_BRIGHTNESS = 0x10, ///< Standard VCP opcode for brightness
VCP_CONTRAST = 0x12, ///< Standard VCP opcode for contrast
VCP_INPUT_SOURCE = 0x60 ///< Standard VCP opcode for input
};
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
check_edid (int fd, struct error **e)
{
uint8_t edid_req[] = { 0x00 };
uint8_t buf[8] = "";
struct i2c_msg bufs[] =
{
{ .addr = 0x50, .flags = 0,
.len = 1, .buf = edid_req },
{ .addr = 0x50, .flags = I2C_M_RD,
.len = sizeof buf, .buf = buf },
};
struct i2c_rdwr_ioctl_data data;
data.msgs = bufs;
data.nmsgs = 2;
if (ioctl (fd, I2C_RDWR, &data) < 0)
return error_set (e, "%s: %s", "ioctl", strerror (errno));
if (memcmp ("\x00\xFF\xFF\xFF\xFF\xFF\xFF\x00", buf, sizeof buf))
return error_set (e, "invalid EDID");
return true;
}
static bool
is_a_display (int fd, struct error **e)
{
struct stat st;
if (fstat (fd, &st) < 0)
return error_set (e, "%s: %s", "fstat", strerror (errno));
unsigned long funcs;
if (!(st.st_mode & S_IFCHR)
|| ioctl (fd, I2C_FUNCS, &funcs) < 0
|| !(funcs & I2C_FUNC_I2C))
return error_set (e, "not an I2C device");
return check_edid (fd, e);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
ddc_send (int fd, unsigned command, void *args, size_t args_len,
struct error **e)
{
struct str buf;
str_init (&buf);
str_pack_u8 (&buf, DDC_ADDRESS_HOST | I2C_READ);
str_pack_u8 (&buf, DDC_LENGTH_XOR | (args_len + 1));
str_pack_u8 (&buf, command);
str_append_data (&buf, args, args_len);
unsigned xor = DDC_ADDRESS_DISPLAY;
for (size_t i = 0; i < buf.len; i++)
xor ^= buf.str[i];
str_pack_u8 (&buf, xor);
struct i2c_msg msg =
{
// The driver unshifts it back
.addr = DDC_ADDRESS_DISPLAY >> 1, .flags = 0,
.len = buf.len, .buf = (uint8_t *) buf.str,
};
struct i2c_rdwr_ioctl_data data;
data.msgs = &msg;
data.nmsgs = 1;
bool failed = ioctl (fd, I2C_RDWR, &data) < 0;
str_free (&buf);
if (failed)
return error_set (e, "%s: %s", "ioctl", strerror (errno));
return true;
}
static bool
ddc_read (int fd, unsigned *command, void *out_buf, size_t *n_read,
struct error **e)
{
uint8_t buf[128] = "";
struct i2c_msg msg =
{
// The driver unshifts it back
.addr = DDC_ADDRESS_DISPLAY >> 1, .flags = I2C_M_RD,
.len = sizeof buf, .buf = buf,
};
struct i2c_rdwr_ioctl_data data;
data.msgs = &msg;
data.nmsgs = 1;
if (ioctl (fd, I2C_RDWR, &data) < 0)
return error_set (e, "%s: %s", "ioctl", strerror (errno));
struct msg_unpacker unpacker;
msg_unpacker_init (&unpacker, buf, sizeof buf);
uint8_t sender, length, cmd;
(void) msg_unpacker_u8 (&unpacker, &sender);
(void) msg_unpacker_u8 (&unpacker, &length);
(void) msg_unpacker_u8 (&unpacker, &cmd);
if (sender != (DDC_ADDRESS_DISPLAY | I2C_WRITE) || !(length & 0x80))
return error_set (e, "invalid response");
if (!(length ^= 0x80))
return error_set (e, "NULL response");
// TODO: also check the checksum
*command = cmd;
memcpy (out_buf, unpacker.data + unpacker.offset, (*n_read = length - 1));
return true;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct vcp_feature_readout
{
uint8_t type; ///< Type of the value
int16_t max; ///< Maximum value
int16_t cur; ///< Current value
};
static bool
vcp_get_feature (int fd, uint8_t feature, struct vcp_feature_readout *out,
struct error **e)
{
uint8_t get_req[] = { feature };
if (!ddc_send (fd, DDC_GET_VCP_FEATURE, get_req, sizeof get_req, e))
return false;
wait_ms (40);
unsigned command = 0;
uint8_t buf[128] = "";
size_t len = 0;
if (!ddc_read (fd, &command, buf, &len, e))
return false;
if (command != DDC_GET_VCP_FEATURE_REPLY || len != 7)
return error_set (e, "invalid response");
struct msg_unpacker unpacker;
msg_unpacker_init (&unpacker, buf, len);
uint8_t result; msg_unpacker_u8 (&unpacker, &result);
uint8_t vcp_opcode; msg_unpacker_u8 (&unpacker, &vcp_opcode);
msg_unpacker_u8 (&unpacker, &out->type);
msg_unpacker_i16 (&unpacker, &out->max);
msg_unpacker_i16 (&unpacker, &out->cur);
if (result == 0x01)
return error_set (e, "error reported by monitor");
if (result != 0x00
|| vcp_opcode != feature)
return error_set (e, "invalid response");
// These are unsigned but usually just one byte long
if (out->max < 0 || out->cur < 0)
return error_set (e, "capability range overflow");
return true;
}
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