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drm: edid: add support for E-DDC 

The current logic for probing ddc is limited to
2 blocks (256 bytes), this patch adds support
for the 4 block (512) data.

To do this, a single 8-bit segment index is
passed to the display via the I2C address 30h.
Data from the selected segment is then immediately
read via the regular DDC2 address using a repeated
I2C 'START' signal.

Signed-off-by: Shirish S <s.shirish@samsung.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
hifive-unleashed-5.1
Shirish S 2012-08-30 07:04:06 +00:00 committed by Dave Airlie
parent 93eb58d53f
commit cd004b3f4c
1 changed files with 16 additions and 3 deletions
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19
drivers/gpu/drm/drm_edid.c
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@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
int block, int len)
{
unsigned char start = block * EDID_LENGTH;
unsigned char segment = block >> 1;
unsigned char xfers = segment ? 3 : 2;
int ret, retries = 5;
/* The core i2c driver will automatically retry the transfer if the
@ -265,6 +267,11 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
do {
struct i2c_msg msgs[] = {
{
.addr = DDC_SEGMENT_ADDR,
.flags = 0,
.len = 1,
.buf = &segment,
}, {
.addr = DDC_ADDR,
.flags = 0,
.len = 1,
@ -276,15 +283,21 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
.buf = buf,
}
};
ret = i2c_transfer(adapter, msgs, 2);
/*
* Avoid sending the segment addr to not upset non-compliant ddc
* monitors.
*/
ret = i2c_transfer(adapter, &msgs[3 - xfers], xfers);
if (ret == -ENXIO) {
DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",
adapter->name);
break;
}
} while (ret != 2 && --retries);
} while (ret != xfers && --retries);
return ret == 2 ? 0 : -1;
return ret == xfers ? 0 : -1;
}
static bool drm_edid_is_zero(u8 *in_edid, int length)