Commit cd004b3f authored by Shirish S's avatar Shirish S Committed by Dave Airlie
Browse files

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: default avatarShirish S <s.shirish@samsung.com>
Reviewed-by: default avatarJean Delvare <jdelvare@suse.de>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: default avatarVille Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 93eb58d5

drivers/gpu/drm/drm_edid.c

+16 −3
Original line number Diff line number Diff line
@@ -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)

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