[PATCH 05/10] drm/i915 & drm/xe: save struct drm_device to drvdata

Fri Aug 2 12:08:17 UTC 2024

Quoting Jani Nikula (2024-08-02 05:18:39-03:00)
>On Thu, 01 Aug 2024, Gustavo Sousa <gustavo.sousa at intel.com> wrote:
>> Quoting Jani Nikula (2024-07-29 11:30:06-03:00)
>>>In the future, the display code shall not have any idea about struct
>>>xe_device or struct drm_i915_private, but will need to get at the struct
>>>drm_device via drvdata. Store the struct drm_device pointer to drvdata
>>>instead of the driver specific pointer.
>>>
>>>Even though struct drm_device is embedded in both struct xe_device and
>>>struct drm_i915_private at offset 0, take care to check for NULL before
>>>using container_of() to allow for other offsets.
>>
>> I think the second half of this paragraph could be rephrased. One might
>> think that the text is suggesting that checking for NULL has something
>> to do with allowing other offsets.
>>
>> I would jump directly to mention using container_of() and would assume
>> that it is implied that NULL check is necessary before using it. :-)
>
>But I *am* suggesting the NULL check before container_of() has
>everything to do with allowing other offsets!
>
>container_of() will return a NULL pointer for a NULL pointer when the
>offset is 0, but will return a negative garbage pointer otherwise.

Okay, I think I got a better understanding of what you mean.

That said, the following makes more sense *to me*:

- The use of container_of() is what actually allows the use of non-zero
  offsets.

- container_of() shouldn't be used with NULL pointers, it just doesn't
  make sense. So, if we receive a NULL pointer, don't bother using
  container_of() and simply return NULL.

--
Gustavo Sousa

>
>BR,
>Jani.
>
>
>>
>> Reviewed-by: Gustavo Sousa <gustavo.sousa at intel.com>
>>
>>>
>>>Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>>>---
>>> drivers/gpu/drm/i915/i915_driver.c                | 2 +-
>>> drivers/gpu/drm/i915/i915_drv.h                   | 8 ++++++--
>>> drivers/gpu/drm/i915/selftests/mock_gem_device.c  | 2 +-
>>> drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h | 4 +++-
>>> drivers/gpu/drm/xe/xe_device.h                    | 8 ++++++--
>>> drivers/gpu/drm/xe/xe_pci.c                       | 2 +-
>>> 6 files changed, 18 insertions(+), 8 deletions(-)
>>>
>>>diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
>>>index fb8e9c2fcea5..176c13c2e191 100644
>>>--- a/drivers/gpu/drm/i915/i915_driver.c
>>>+++ b/drivers/gpu/drm/i915/i915_driver.c
>>>@@ -723,7 +723,7 @@ i915_driver_create(struct pci_dev *pdev, const struct pci_device_id *ent)
>>>         if (IS_ERR(i915))
>>>                 return i915;
>>> 
>>>-        pci_set_drvdata(pdev, i915);
>>>+        pci_set_drvdata(pdev, &i915->drm);
>>> 
>>>         /* Device parameters start as a copy of module parameters. */
>>>         i915_params_copy(&i915->params, &i915_modparams);
>>>diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>>index d7723dd11c80..f6edaef73db5 100644
>>>--- a/drivers/gpu/drm/i915/i915_drv.h
>>>+++ b/drivers/gpu/drm/i915/i915_drv.h
>>>@@ -365,12 +365,16 @@ static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
>>> 
>>> static inline struct drm_i915_private *kdev_to_i915(struct device *kdev)
>>> {
>>>-        return dev_get_drvdata(kdev);
>>>+        struct drm_device *drm = dev_get_drvdata(kdev);
>>>+
>>>+        return drm ? to_i915(drm) : NULL;
>>> }
>>> 
>>> static inline struct drm_i915_private *pdev_to_i915(struct pci_dev *pdev)
>>> {
>>>-        return pci_get_drvdata(pdev);
>>>+        struct drm_device *drm = pci_get_drvdata(pdev);
>>>+
>>>+        return drm ? to_i915(drm) : NULL;
>>> }
>>> 
>>> static inline struct intel_gt *to_gt(const struct drm_i915_private *i915)
>>>diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
>>>index 0bd29846873b..91794ca17a58 100644
>>>--- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
>>>+++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
>>>@@ -172,7 +172,7 @@ struct drm_i915_private *mock_gem_device(void)
>>>                 return NULL;
>>>         }
>>> 
>>>-        pci_set_drvdata(pdev, i915);
>>>+        pci_set_drvdata(pdev, &i915->drm);
>>> 
>>>         /* Device parameters start as a copy of module parameters. */
>>>         i915_params_copy(&i915->params, &i915_modparams);
>>>diff --git a/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h b/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h
>>>index 2feedddf1e40..766fba88a3c8 100644
>>>--- a/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h
>>>+++ b/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h
>>>@@ -23,7 +23,9 @@ static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
>>> 
>>> static inline struct drm_i915_private *kdev_to_i915(struct device *kdev)
>>> {
>>>-        return dev_get_drvdata(kdev);
>>>+        struct drm_device *drm = dev_get_drvdata(kdev);
>>>+
>>>+        return drm ? to_i915(drm) : NULL;
>>> }
>>> 
>>> #define IS_PLATFORM(xe, x) ((xe)->info.platform == x)
>>>diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
>>>index 2c96f1b2aafd..022876eebfd5 100644
>>>--- a/drivers/gpu/drm/xe/xe_device.h
>>>+++ b/drivers/gpu/drm/xe/xe_device.h
>>>@@ -17,12 +17,16 @@ static inline struct xe_device *to_xe_device(const struct drm_device *dev)
>>> 
>>> static inline struct xe_device *kdev_to_xe_device(struct device *kdev)
>>> {
>>>-        return dev_get_drvdata(kdev);
>>>+        struct drm_device *drm = dev_get_drvdata(kdev);
>>>+
>>>+        return drm ? to_xe_device(drm) : NULL;
>>> }
>>> 
>>> static inline struct xe_device *pdev_to_xe_device(struct pci_dev *pdev)
>>> {
>>>-        return pci_get_drvdata(pdev);
>>>+        struct drm_device *drm = pci_get_drvdata(pdev);
>>>+
>>>+        return drm ? to_xe_device(drm) : NULL;
>>> }
>>> 
>>> static inline struct xe_device *xe_device_const_cast(const struct xe_device *xe)
>>>diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
>>>index 7bb811b4a057..f861b8cf931a 100644
>>>--- a/drivers/gpu/drm/xe/xe_pci.c
>>>+++ b/drivers/gpu/drm/xe/xe_pci.c
>>>@@ -800,7 +800,7 @@ static int xe_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>>>         if (IS_ERR(xe))
>>>                 return PTR_ERR(xe);
>>> 
>>>-        pci_set_drvdata(pdev, xe);
>>>+        pci_set_drvdata(pdev, &xe->drm);
>>> 
>>>         xe_pm_assert_unbounded_bridge(xe);
>>>         subplatform_desc = find_subplatform(xe, desc);
>>>-- 
>>>2.39.2
>>>
>
>-- 
>Jani Nikula, Intel