| Message ID | 20191002124354.v2.1.I709dfec496f5f0b44a7b61dcd4937924da8d8382@changeid (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/bridge: dw-hdmi: Refuse DDC/CI transfers on the internal I2C controller | expand |
Hi Matthias, On 02/10/2019 21:44, Matthias Kaehlcke wrote: > The DDC/CI protocol involves sending a multi-byte request to the > display via I2C, which is typically followed by a multi-byte > response. The internal I2C controller only allows single byte > reads/writes or reads of 8 sequential bytes, hence DDC/CI is not > supported when the internal I2C controller is used. The I2C > transfers complete without errors, however the data in the response > is garbage. Abort transfers to/from slave address 0x37 (DDC) with > -EOPNOTSUPP, to make it evident that the communication is failing. > > Signed-off-by: Matthias Kaehlcke <mka@chromium.org> > Reviewed-by: Douglas Anderson <dianders@chromium.org> > Reviewed-by: Sean Paul <sean@poorly.run> > Acked-by: Neil Armstrong <narmstrong@baylibre.com> > --- > Sorry for the delay with sending v2, I completely forgot about this patch ... > > Changes in v2: > - updated comment with 'TOFIX' entry as requested by Neil > - added Neil's 'Acked-by' tag > > drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c > index 52d220a70362..ac24bceaf415 100644 > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c > @@ -41,6 +41,7 @@ > > #include <media/cec-notifier.h> > > +#define DDC_CI_ADDR 0x37 > #define DDC_SEGMENT_ADDR 0x30 > > #define HDMI_EDID_LEN 512 > @@ -439,6 +440,15 @@ static int dw_hdmi_i2c_xfer(struct i2c_adapter *adap, > u8 addr = msgs[0].addr; > int i, ret = 0; > > + if (addr == DDC_CI_ADDR) > + /* > + * The internal I2C controller does not support the multi-byte > + * read and write operations needed for DDC/CI. > + * TOFIX: Blacklist the DDC/CI address until we filter out > + * unsupported I2C operations. > + */ > + return -EOPNOTSUPP; > + > dev_dbg(hdmi->dev, "xfer: num: %d, addr: %#x\n", num, addr); > > for (i = 0; i < num; i++) { > Applying to drm-misc-next Thanks ! Neil
diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c index 52d220a70362..ac24bceaf415 100644 --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c @@ -41,6 +41,7 @@ #include <media/cec-notifier.h> +#define DDC_CI_ADDR 0x37 #define DDC_SEGMENT_ADDR 0x30 #define HDMI_EDID_LEN 512 @@ -439,6 +440,15 @@ static int dw_hdmi_i2c_xfer(struct i2c_adapter *adap, u8 addr = msgs[0].addr; int i, ret = 0; + if (addr == DDC_CI_ADDR) + /* + * The internal I2C controller does not support the multi-byte + * read and write operations needed for DDC/CI. + * TOFIX: Blacklist the DDC/CI address until we filter out + * unsupported I2C operations. + */ + return -EOPNOTSUPP; + dev_dbg(hdmi->dev, "xfer: num: %d, addr: %#x\n", num, addr); for (i = 0; i < num; i++) {