> Author: gonzo
> Date: Wed Jun 10 21:38:35 2020
> New Revision: 362029
> URL: https://svnweb.freebsd.org/changeset/base/362029
>
> Log:
> Fix reading EDID on TVs/monitors without E-DCC support
>
> Writing segment id to I2C device 0x30 only required if the segment is
> non-zero. On the devices without E-DCC support writing to that address
> fails and whole transaction then fails too. To avoid this do
> not attempt write to the segment selection device unless required.
>
> MFC after: 2 weeks
Is it possible that this bad write is what has caused me to corrupt
the EDID of 3 monitors over the last year while using a Display
Port to HDMI cable on them?
> Modified:
> head/sys/dev/hdmi/dwc_hdmi.c
>
> Modified: head/sys/dev/hdmi/dwc_hdmi.c
> ==============================================================================
> --- head/sys/dev/hdmi/dwc_hdmi.c Wed Jun 10 21:18:19 2020
> (r362028)
> +++ head/sys/dev/hdmi/dwc_hdmi.c Wed Jun 10 21:38:35 2020
> (r362029)
> @@ -658,6 +658,11 @@ hdmi_edid_read(struct dwc_hdmi_softc *sc, int block, u
> int result;
> uint8_t addr = block & 1 ? EDID_LENGTH : 0;
> uint8_t segment = block >> 1;
> + /*
> + * Some devices do not support E-DDC so attempt
> + * writing segment address only if it's neccessary
> + */
> + unsigned char xfers = segment ? 3 : 2;
> struct iic_msg msg[] = {
> { I2C_DDC_SEGADDR, IIC_M_WR, 1, &segment },
> { I2C_DDC_ADDR, IIC_M_WR, 1, &addr },
> @@ -687,7 +692,7 @@ hdmi_edid_read(struct dwc_hdmi_softc *sc, int block, u
> return (result);
> }
>
> - result = iicbus_transfer(i2c_dev, msg, 3);
> + result = iicbus_transfer(i2c_dev, &msg[3 - xfers], xfers);
> iicbus_release_bus(i2c_dev, sc->sc_dev);
>
> if (result) {
>
--
Rod Grimes rgri...@freebsd.org
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