From: Douglas Anderson <dianders@chromium.org> To: Andrzej Hajda <a.hajda@samsung.com>, Neil Armstrong <narmstrong@baylibre.com>, Laurent Pinchart <Laurent.pinchart@ideasonboard.com>, Jonas Karlman <jonas@kwiboo.se>, Jernej Skrabec <jernej.skrabec@siol.net>, Sam Ravnborg <sam@ravnborg.org>, Wolfram Sang <wsa@kernel.org> Cc: Lyude Paul <lyude@redhat.com>, Steev Klimaszewski <steev@kali.org>, Stephen Boyd <swboyd@chromium.org>, Bjorn Andersson <bjorn.andersson@linaro.org>, linux-arm-msm@vger.kernel.org, Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>, Linus W <linus.walleij@linaro.org>, robdclark@chromium.org, Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Thierry Reding <treding@nvidia.com>, linux-i2c@vger.kernel.org, dri-devel@lists.freedesktop.org, Douglas Anderson <dianders@chromium.org>, linux-kernel@vger.kernel.org Subject: [PATCH v6 1/5] i2c: i2c-core-of: Fix corner case of finding adapter by node Date: Mon, 3 May 2021 14:58:40 -0700 [thread overview] Message-ID: <20210503145750.v6.1.Ib7e3a4af2f3e2cb3bd8e4adbac3bcfc966f27791@changeid> (raw) In-Reply-To: <20210503215844.2996320-1-dianders@chromium.org> The of_find_i2c_adapter_by_node() could end up failing to find an adapter in certain conditions. Specifically it's possible that of_dev_or_parent_node_match() could end up finding an I2C client in the list and cause bus_find_device() to stop early even though an I2C adapter was present later in the list. Let's move the i2c_verify_adapter() into the predicate function to prevent this. Now we'll properly skip over the I2C client and be able to find the I2C adapter. This issue has always been a potential problem if a single device tree node could represent both an I2C client and an adapter. I believe this is a sane thing to do if, for instance, an I2C-connected DP bridge chip is present. The bridge chip is an I2C client but it can also provide an I2C adapter (DDC tunneled over AUX channel). We don't want to have to create a sub-node just so a panel can link to it with the "ddc-i2c-bus" property. I believe that this problem got worse, however, with commit e814e688413a ("i2c: of: Try to find an I2C adapter matching the parent"). Starting at that commit it would be even easier to accidentally miss finding the adapter. Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> --- Later patches in this series won't work right without this one, but they won't crash. If we can't find the i2c bus we'll just fall back to the hardcoded panel modes which, at least today, all panels have. I'll also note that part of me wonders if we should actually fix this further to run two passes through everything: first look to see if we find an exact match and only look at the parent pointer if there is no match. I don't currently have a need for that and it's a slightly bigger change, but it seems conceivable that it could affect someone? (no changes since v1) drivers/i2c/i2c-core-of.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c index 3ed74aa4b44b..de0bf5fce3a2 100644 --- a/drivers/i2c/i2c-core-of.c +++ b/drivers/i2c/i2c-core-of.c @@ -124,6 +124,14 @@ static int of_dev_or_parent_node_match(struct device *dev, const void *data) return 0; } +static int of_i2c_adapter_match(struct device *dev, const void *data) +{ + if (!of_dev_or_parent_node_match(dev, data)) + return 0; + + return !!i2c_verify_adapter(dev); +} + /* must call put_device() when done with returned i2c_client device */ struct i2c_client *of_find_i2c_device_by_node(struct device_node *node) { @@ -146,18 +154,13 @@ EXPORT_SYMBOL(of_find_i2c_device_by_node); struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node) { struct device *dev; - struct i2c_adapter *adapter; dev = bus_find_device(&i2c_bus_type, NULL, node, - of_dev_or_parent_node_match); + of_i2c_adapter_match); if (!dev) return NULL; - adapter = i2c_verify_adapter(dev); - if (!adapter) - put_device(dev); - - return adapter; + return to_i2c_adapter(dev); } EXPORT_SYMBOL(of_find_i2c_adapter_by_node); -- 2.31.1.527.g47e6f16901-goog
WARNING: multiple messages have this Message-ID (diff)
From: Douglas Anderson <dianders@chromium.org> To: Andrzej Hajda <a.hajda@samsung.com>, Neil Armstrong <narmstrong@baylibre.com>, Laurent Pinchart <Laurent.pinchart@ideasonboard.com>, Jonas Karlman <jonas@kwiboo.se>, Jernej Skrabec <jernej.skrabec@siol.net>, Sam Ravnborg <sam@ravnborg.org>, Wolfram Sang <wsa@kernel.org> Cc: robdclark@chromium.org, Thierry Reding <treding@nvidia.com>, dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, Douglas Anderson <dianders@chromium.org>, Steev Klimaszewski <steev@kali.org>, Bjorn Andersson <bjorn.andersson@linaro.org>, Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>, linux-i2c@vger.kernel.org, Stephen Boyd <swboyd@chromium.org>, linux-kernel@vger.kernel.org Subject: [PATCH v6 1/5] i2c: i2c-core-of: Fix corner case of finding adapter by node Date: Mon, 3 May 2021 14:58:40 -0700 [thread overview] Message-ID: <20210503145750.v6.1.Ib7e3a4af2f3e2cb3bd8e4adbac3bcfc966f27791@changeid> (raw) In-Reply-To: <20210503215844.2996320-1-dianders@chromium.org> The of_find_i2c_adapter_by_node() could end up failing to find an adapter in certain conditions. Specifically it's possible that of_dev_or_parent_node_match() could end up finding an I2C client in the list and cause bus_find_device() to stop early even though an I2C adapter was present later in the list. Let's move the i2c_verify_adapter() into the predicate function to prevent this. Now we'll properly skip over the I2C client and be able to find the I2C adapter. This issue has always been a potential problem if a single device tree node could represent both an I2C client and an adapter. I believe this is a sane thing to do if, for instance, an I2C-connected DP bridge chip is present. The bridge chip is an I2C client but it can also provide an I2C adapter (DDC tunneled over AUX channel). We don't want to have to create a sub-node just so a panel can link to it with the "ddc-i2c-bus" property. I believe that this problem got worse, however, with commit e814e688413a ("i2c: of: Try to find an I2C adapter matching the parent"). Starting at that commit it would be even easier to accidentally miss finding the adapter. Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> --- Later patches in this series won't work right without this one, but they won't crash. If we can't find the i2c bus we'll just fall back to the hardcoded panel modes which, at least today, all panels have. I'll also note that part of me wonders if we should actually fix this further to run two passes through everything: first look to see if we find an exact match and only look at the parent pointer if there is no match. I don't currently have a need for that and it's a slightly bigger change, but it seems conceivable that it could affect someone? (no changes since v1) drivers/i2c/i2c-core-of.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c index 3ed74aa4b44b..de0bf5fce3a2 100644 --- a/drivers/i2c/i2c-core-of.c +++ b/drivers/i2c/i2c-core-of.c @@ -124,6 +124,14 @@ static int of_dev_or_parent_node_match(struct device *dev, const void *data) return 0; } +static int of_i2c_adapter_match(struct device *dev, const void *data) +{ + if (!of_dev_or_parent_node_match(dev, data)) + return 0; + + return !!i2c_verify_adapter(dev); +} + /* must call put_device() when done with returned i2c_client device */ struct i2c_client *of_find_i2c_device_by_node(struct device_node *node) { @@ -146,18 +154,13 @@ EXPORT_SYMBOL(of_find_i2c_device_by_node); struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node) { struct device *dev; - struct i2c_adapter *adapter; dev = bus_find_device(&i2c_bus_type, NULL, node, - of_dev_or_parent_node_match); + of_i2c_adapter_match); if (!dev) return NULL; - adapter = i2c_verify_adapter(dev); - if (!adapter) - put_device(dev); - - return adapter; + return to_i2c_adapter(dev); } EXPORT_SYMBOL(of_find_i2c_adapter_by_node); -- 2.31.1.527.g47e6f16901-goog _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2021-05-03 21:59 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-03 21:58 [PATCH v6 0/5] drm: Fix EDID reading on ti-sn65dsi86; solve some chicken-and-egg problems Douglas Anderson 2021-05-03 21:58 ` Douglas Anderson 2021-05-03 21:58 ` Douglas Anderson [this message] 2021-05-03 21:58 ` [PATCH v6 1/5] i2c: i2c-core-of: Fix corner case of finding adapter by node Douglas Anderson 2021-05-17 20:16 ` Doug Anderson 2021-05-17 20:16 ` Doug Anderson 2021-05-03 21:58 ` [PATCH v6 2/5] drm/dp: Allow an early call to register DDC i2c bus Douglas Anderson 2021-05-03 21:58 ` Douglas Anderson 2021-05-07 21:18 ` Lyude Paul 2021-05-07 21:18 ` Lyude Paul 2021-05-07 22:00 ` Bjorn Andersson 2021-05-07 22:00 ` Bjorn Andersson 2021-05-07 22:09 ` Lyude Paul 2021-05-07 22:09 ` Lyude Paul 2021-05-14 11:16 ` Jani Nikula 2021-05-14 11:16 ` Jani Nikula 2021-05-17 20:17 ` Doug Anderson 2021-05-17 20:17 ` Doug Anderson 2021-05-03 21:58 ` [PATCH v6 3/5] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson 2021-05-03 21:58 ` Douglas Anderson 2021-05-03 21:58 ` [PATCH v6 4/5] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC Douglas Anderson 2021-05-03 21:58 ` Douglas Anderson 2021-05-03 21:58 ` [PATCH v6 5/5] arm64: dts: qcom: Link the panel to the bridge's DDC bus Douglas Anderson 2021-05-03 21:58 ` Douglas Anderson
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