accel: add dedicated minor for accelerator devices

The accelerator devices are exposed to user-space using a dedicated
major. In addition, they are represented in /dev with new, dedicated
device char names: /dev/accel/accel*. This is done to make sure any
user-space software that tries to open a graphic card won't open
the accelerator device by mistake.

The above implies that the minor numbering should be separated from
the rest of the DRM devices. However, to avoid code duplication, we
want the drm_minor structure to be able to represent the accelerator
device.

To achieve this, we add a new drm_minor* to drm_device that represents
the accelerator device. This pointer is initialized for drivers that
declare they handle compute accelerator, using a new driver feature
flag called DRIVER_COMPUTE_ACCEL. It is important to note that this
driver feature is mutually exclusive with DRIVER_RENDER. Devices that
want to expose both graphics and compute device char files should be
handled by two drivers that are connected using the auxiliary bus
framework.

In addition, we define a different IDR to handle the accelerators
minors. This is done to make the minor's index be identical to the
device index in /dev/. Any access to the IDR is done solely
by functions in accel_drv.c, as the IDR is define as static. The
DRM core functions call those functions in case they detect the minor's
type is DRM_MINOR_ACCEL.

We define a separate accel_open function (from drm_open) that the
accel drivers should set as their open callback function. Both these
functions eventually call the same drm_open_helper(), which had to be
changed to be non-static so it can be called from accel_drv.c.
accel_open() only partially duplicates drm_open as I removed some code
from it that handles legacy devices.

To help new drivers, I defined DEFINE_DRM_ACCEL_FOPS macro to easily
set the required function operations pointers structure.

Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Tested-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>

4 files changed, 96 insertions, 1 deletions

diff --git a/include/drm/drm_accel.h b/include/drm/drm_accel.h
index e1758f484278..65c0affbd306 100644
--- a/include/drm/drm_accel.h
+++ b/include/drm/drm_accel.h
@@ -8,12 +8,56 @@
 #ifndef DRM_ACCEL_H_
 #define DRM_ACCEL_H_
 
+#include <drm/drm_file.h>
+
 #define ACCEL_MAJOR		261
+#define ACCEL_MAX_MINORS	256
+
+/**
+ * DRM_ACCEL_FOPS - Default drm accelerators file operations
+ *
+ * This macro provides a shorthand for setting the accelerator file ops in the
+ * &file_operations structure.  If all you need are the default ops, use
+ * DEFINE_DRM_ACCEL_FOPS instead.
+ */
+#define DRM_ACCEL_FOPS \
+	.open		= accel_open,\
+	.release	= drm_release,\
+	.unlocked_ioctl	= drm_ioctl,\
+	.compat_ioctl	= drm_compat_ioctl,\
+	.poll		= drm_poll,\
+	.read		= drm_read,\
+	.llseek		= noop_llseek
+
+/**
+ * DEFINE_DRM_ACCEL_FOPS() - macro to generate file operations for accelerators drivers
+ * @name: name for the generated structure
+ *
+ * This macro autogenerates a suitable &struct file_operations for accelerators based
+ * drivers, which can be assigned to &drm_driver.fops. Note that this structure
+ * cannot be shared between drivers, because it contains a reference to the
+ * current module using THIS_MODULE.
+ *
+ * Note that the declaration is already marked as static - if you need a
+ * non-static version of this you're probably doing it wrong and will break the
+ * THIS_MODULE reference by accident.
+ */
+#define DEFINE_DRM_ACCEL_FOPS(name) \
+	static const struct file_operations name = {\
+		.owner		= THIS_MODULE,\
+		DRM_ACCEL_FOPS,\
+	}
 
 #if IS_ENABLED(CONFIG_DRM_ACCEL)
 
 void accel_core_exit(void);
 int accel_core_init(void);
+void accel_minor_remove(int index);
+int accel_minor_alloc(void);
+void accel_minor_replace(struct drm_minor *minor, int index);
+void accel_set_device_instance_params(struct device *kdev, int index);
+int accel_open(struct inode *inode, struct file *filp);
+void accel_debugfs_init(struct drm_minor *minor, int minor_id);
 
 #else
 
@@ -27,6 +71,27 @@ static inline int __init accel_core_init(void)
 	return 0;
 }
 
+static inline void accel_minor_remove(int index)
+{
+}
+
+static inline int accel_minor_alloc(void)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void accel_minor_replace(struct drm_minor *minor, int index)
+{
+}
+
+static inline void accel_set_device_instance_params(struct device *kdev, int index)
+{
+}
+
+static inline void accel_debugfs_init(struct drm_minor *minor, int minor_id)
+{
+}
+
 #endif /* IS_ENABLED(CONFIG_DRM_ACCEL) */
 
 #endif /* DRM_ACCEL_H_ */
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index 9923c7a6885e..933ce2048e20 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -93,6 +93,9 @@ struct drm_device {
 	/** @render: Render node */
 	struct drm_minor *render;
 
+	/** @accel: Compute Acceleration node */
+	struct drm_minor *accel;
+
 	/**
 	 * @registered:
 	 *
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 700d3857e088..d7c521e8860f 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -96,6 +96,14 @@ enum drm_driver_feature {
 	 * synchronization of command submission.
 	 */
 	DRIVER_SYNCOBJ_TIMELINE         = BIT(6),
+	/**
+	 * @DRIVER_COMPUTE_ACCEL:
+	 *
+	 * Driver supports compute acceleration devices. This flag is mutually exclusive with
+	 * @DRIVER_RENDER and @DRIVER_MODESET. Devices that support both graphics and compute
+	 * acceleration should be handled by two drivers that are connected using auxiliary bus.
+	 */
+	DRIVER_COMPUTE_ACCEL            = BIT(7),
 
 	/* IMPORTANT: Below are all the legacy flags, add new ones above. */
 
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index d780fd151789..0d1f853092ab 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -51,11 +51,15 @@ struct file;
 
 /* Note that the order of this enum is ABI (it determines
  * /dev/dri/renderD* numbers).
+ *
+ * Setting DRM_MINOR_ACCEL to 32 gives enough space for more drm minors to
+ * be implemented before we hit any future
  */
 enum drm_minor_type {
 	DRM_MINOR_PRIMARY,
 	DRM_MINOR_CONTROL,
 	DRM_MINOR_RENDER,
+	DRM_MINOR_ACCEL = 32,
 };
 
 /**
@@ -70,7 +74,7 @@ enum drm_minor_type {
 struct drm_minor {
 	/* private: */
 	int index;			/* Minor device number */
-	int type;                       /* Control or render */
+	int type;                       /* Control or render or accel */
 	struct device *kdev;		/* Linux device */
 	struct drm_device *dev;
 
@@ -397,7 +401,22 @@ static inline bool drm_is_render_client(const struct drm_file *file_priv)
 	return file_priv->minor->type == DRM_MINOR_RENDER;
 }
 
+/**
+ * drm_is_accel_client - is this an open file of the compute acceleration node
+ * @file_priv: DRM file
+ *
+ * Returns true if this is an open file of the compute acceleration node, i.e.
+ * &drm_file.minor of @file_priv is a accel minor.
+ *
+ * See also the :ref:`section on accel nodes <drm_accel_node>`.
+ */
+static inline bool drm_is_accel_client(const struct drm_file *file_priv)
+{
+	return file_priv->minor->type == DRM_MINOR_ACCEL;
+}
+
 int drm_open(struct inode *inode, struct file *filp);
+int drm_open_helper(struct file *filp, struct drm_minor *minor);
 ssize_t drm_read(struct file *filp, char __user *buffer,
 		 size_t count, loff_t *offset);
 int drm_release(struct inode *inode, struct file *filp);