Re: [PATCH V6] drm: edid: add support for E-DDC

[Shirish S <shirish.s12@xxxxxxxxx>]

Gentle Reminder!

On Mon, Sep 3, 2012 at 9:24 PM, Shirish S <shirish.s12@xxxxxxxxx> wrote:

Hello Dave,

My patch-set for adding support for 4 block EDID is now reviewed and ready.

Please let me know if you want any further clarification

Regards,

Shirish S

On Thu, Aug 30, 2012 at 12:04 AM, Shirish S <s.shirish@xxxxxxxxxxx> wrote:

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@xxxxxxxxxxx>
Reviewed-by: Jean Delvare <jdelvare@xxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Reviewed-by: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
---

 drivers/gpu/drm/drm_edid.c |   19 ++++++++++++++++---
 1 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index bcc4725..7f62de5 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -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)
--
1.7.0.4

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