Hi all,
Sorry for breaking message threading but I was not included in
iterations 3 and 4 of this patch.
Random comments about v4:
> --- 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
> @@ -264,7 +266,12 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter,
> unsigned char *buf,
> */
> do {
> struct i2c_msg msgs[] = {
> - {
> + { /*set segment pointer */
> + .addr = DDC_SEGMENT_ADDR,
> + .flags = segment ? 0 : I2C_M_IGNORE_NAK,
I don't get the idea. If segment == 0, this message is never sent, so the
value of field flags doesn't matter. So flags will always be 0 when this
message is sent, so it can be hard-coded.
But from previous discussions my understanding was an agreement on always
using I2C_M_IGNORE_NAK for improved compatibility. So I2C_M_IGNORE_NAK
should be hard-coded, not 0?
> + .len = 1,
> + .buf = &segment,
> + }, {
> .addr = DDC_ADDR,
> .flags = 0,
> .len = 1,
> @@ -276,15 +283,22 @@ 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.
> + */
s/segment addr/segment/, plus it's abot E-DCC compliance as I understand it,
not DDC.
> + if (!segment)
> + ret = i2c_transfer(adapter, &msgs[1], xfers);
> + else
> + ret = i2c_transfer(adapter, msgs, xfers);
> +
This can be written:
ret = i2c_transfer(adapter, &msgs[3 - xfers], xfers);
Which is more compact and, I suspect, faster.
> 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)
Other than this, your code looks reasonable, not so different from what
I submitted 8 months ago actually. But ISTU you can test the code with
real hardware while I couldn't.
With the changes above applied, you can add:
Reviewed-by: Jean Delvare <jdelvare@xxxxxxx>
--
Jean Delvare
Suse L3
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