From: Neil Armstrong <narmstrong@baylibre.com>
To: Matthias Kaehlcke <mka@chromium.org>,
Archit Taneja <architt@codeaurora.org>,
Andrzej Hajda <a.hajda@samsung.com>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
David Airlie <airlied@linux.ie>
Cc: Douglas Anderson <dianders@chromium.org>,
Sean Paul <sean@poorly.run>, Yakir Yang <kuankuan.y@gmail.com>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
Tzung-Bi Shih <tzungbi@chromium.org>,
Jerome Brunet <jbrunet@baylibre.com>,
Jernej Skrabec <jernej.skrabec@siol.net>,
Cheng-Yi Chiang <cychiang@chromium.org>
Subject: Re: [PATCH v2] drm/bridge: dw-hdmi: Refuse DDC/CI transfers on the internal I2C controller
Date: Mon, 7 Oct 2019 13:54:05 +0200 [thread overview]
Message-ID: <5640bf2f-a90f-d424-a0d7-1bd19602525d@baylibre.com> (raw)
In-Reply-To: <20191002124354.v2.1.I709dfec496f5f0b44a7b61dcd4937924da8d8382@changeid>
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
next prev parent reply other threads:[~2019-10-07 11:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 19:44 [PATCH v2] drm/bridge: dw-hdmi: Refuse DDC/CI transfers on the internal I2C controller Matthias Kaehlcke
2019-10-07 11:54 ` Neil Armstrong [this message]
-- strict thread matches above, loose matches on Subject: below --
2019-07-22 18:19 Matthias Kaehlcke
2019-07-22 20:12 ` Doug Anderson
2019-07-22 20:54 ` Matthias Kaehlcke
2019-07-22 20:24 ` Sean Paul
2019-07-22 20:57 ` Doug Anderson
2019-07-22 21:02 ` Matthias Kaehlcke
2019-07-25 17:49 ` Sean Paul
2019-07-30 13:38 ` Neil Armstrong
2019-07-30 16:14 ` Sean Paul
2019-07-31 7:38 ` Neil Armstrong
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