On Thu, Sep 13, 2018 at 04:16:21PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> We wish to control certain driver_features flags on a per-device basis
> while still sharing a single drm_driver instance across all the
> devices. To that end introduce device.driver_features. By default
> it will be set to ~0 to not impose any limits beyond
> driver.driver_features. Drivers can then clear specific flags
> in the per-device bitmask to limit the capabilities of the device.
>
> An alternative approach would be to copy the driver_features from
> the driver into the device in drm_dev_init(), however that would
> require verifying that no driver is currently changing
> driver.driver_features after drm_dev_init(). Hence the ~0 apporach
> was easier.
>
> Ideally we'd also make drm_driver const but there is plenty of code
> left that wants to mutate it (eg. various vfunc assignments). We'll
> need to fix all that up before we can make it const.
>
> And while at it fix up the type of the feature flag passed to
> drm_core_check_feature().
>
> v2: Streamline the && vs. & (Chris)
> s/int/u32/ in drm_core_check_feature() args
>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
git grep DRIVER_ATOMIC -- drivers/gpu/drm/nouveau has a 2nd supporting
case for this. Exactly same problem as we have here. Would be good to also
convert that one, for a bit of OCD.
Irrespective of that, on the series:
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Feel free to also add the r-b to the nouveau patch if you do it, it's
rather obvious.
-Daniel
> ---
> drivers/gpu/drm/drm_drv.c | 3 +++
> include/drm/drm_device.h | 10 ++++++++++
> include/drm/drm_drv.h | 8 ++++----
> 3 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index ea4941da9b27..36e8e9cbec52 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -506,6 +506,9 @@ int drm_dev_init(struct drm_device *dev,
> dev->dev = parent;
> dev->driver = driver;
>
> + /* no per-device feature limits by default */
> + dev->driver_features = ~0u;
> +
> INIT_LIST_HEAD(&dev->filelist);
> INIT_LIST_HEAD(&dev->filelist_internal);
> INIT_LIST_HEAD(&dev->clientlist);
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index f9c6e0e3aec7..42411b3ea0c8 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -45,6 +45,16 @@ struct drm_device {
> /* currently active master for this device. Protected by master_mutex */
> struct drm_master *master;
>
> + /**
> + * @driver_features: per-device driver features
> + *
> + * Drivers can clear specific flags here to disallow
> + * certain features on a per-device basis while still
> + * sharing a single &struct drm_driver instance across
> + * all devices.
> + */
> + u32 driver_features;
> +
> /**
> * @unplugged:
> *
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 23b9678137a6..8830e3de3a86 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -653,14 +653,14 @@ static inline bool drm_dev_is_unplugged(struct drm_device *dev)
> * @dev: DRM device to check
> * @feature: feature flag
> *
> - * This checks @dev for driver features, see &drm_driver.driver_features and the
> - * various DRIVER_\* flags.
> + * This checks @dev for driver features, see &drm_driver.driver_features,
> + * &drm_device.driver_features, and the various DRIVER_\* flags.
> *
> * Returns true if the @feature is supported, false otherwise.
> */
> -static inline bool drm_core_check_feature(struct drm_device *dev, int feature)
> +static inline bool drm_core_check_feature(struct drm_device *dev, u32 feature)
> {
> - return dev->driver->driver_features & feature;
> + return dev->driver->driver_features & dev->driver_features & feature;
> }
>
> /**
> --
> 2.16.4
>
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> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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