[PATCH RFC 08/18] accel/qda: Add per-file DRM context and open/close handling

[Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>]

Introduce per-file and per-user context for the QDA DRM accelerator
driver. A new qda_file_priv structure is stored in file->driver_priv
for each open file descriptor, and a qda_user object is allocated per
client with a unique client_id generated from an atomic counter in
qda_dev.

The DRM driver now provides qda_open() and qda_postclose() callbacks.
qda_open() resolves the qda_dev from the drm_device, allocates the
qda_file_priv and qda_user structures, and attaches them to the DRM
file. qda_postclose() tears down the per-file context and frees the
qda_user object when the file is closed.

This prepares the QDA driver to track per-process state for future
features such as per-client memory mappings, job submission contexts,
and access control over DSP compute resources.

Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
---
 drivers/accel/qda/qda_drv.c | 117 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/accel/qda/qda_drv.h |  30 ++++++++++++
 2 files changed, 147 insertions(+)

diff --git a/drivers/accel/qda/qda_drv.c b/drivers/accel/qda/qda_drv.c
index a9113ec78fa2..bf95fc782cf8 100644
--- a/drivers/accel/qda/qda_drv.c
+++ b/drivers/accel/qda/qda_drv.c
@@ -12,11 +12,127 @@
 #include "qda_drv.h"
 #include "qda_rpmsg.h"
 
+static struct qda_drm_priv *get_drm_priv_from_device(struct drm_device *dev)
+{
+	if (!dev)
+		return NULL;
+
+	return (struct qda_drm_priv *)dev->dev_private;
+}
+
+static struct qda_dev *get_qdev_from_drm_device(struct drm_device *dev)
+{
+	struct qda_drm_priv *drm_priv;
+
+	if (!dev) {
+		qda_dbg(NULL, "Invalid drm_device\n");
+		return NULL;
+	}
+
+	drm_priv = get_drm_priv_from_device(dev);
+	if (!drm_priv) {
+		qda_dbg(NULL, "No drm_priv in dev_private\n");
+		return NULL;
+	}
+
+	return drm_priv->qdev;
+}
+
+static struct qda_user *alloc_qda_user(struct qda_dev *qdev)
+{
+	struct qda_user *qda_user;
+
+	qda_user = kzalloc_obj(*qda_user, GFP_KERNEL);
+	if (!qda_user)
+		return NULL;
+
+	qda_user->client_id = atomic_inc_return(&qdev->client_id_counter);
+	qda_user->qda_dev = qdev;
+
+	qda_dbg(qdev, "Allocated qda_user with client_id=%u\n", qda_user->client_id);
+	return qda_user;
+}
+
+static void free_qda_user(struct qda_user *qda_user)
+{
+	if (!qda_user)
+		return;
+
+	qda_dbg(qda_user->qda_dev, "Freeing qda_user client_id=%u\n", qda_user->client_id);
+
+	kfree(qda_user);
+}
+
+static int qda_open(struct drm_device *dev, struct drm_file *file)
+{
+	struct qda_user *qda_user;
+	struct qda_file_priv *qda_file_priv;
+	struct qda_dev *qdev;
+
+	if (!file) {
+		qda_dbg(NULL, "Invalid file pointer\n");
+		return -EINVAL;
+	}
+
+	qdev = get_qdev_from_drm_device(dev);
+	if (!qdev) {
+		qda_dbg(NULL, "Failed to get qdev from drm_device\n");
+		return -EINVAL;
+	}
+
+	qda_file_priv = kzalloc(sizeof(*qda_file_priv), GFP_KERNEL);
+	if (!qda_file_priv)
+		return -ENOMEM;
+
+	qda_file_priv->pid = current->pid;
+
+	qda_user = alloc_qda_user(qdev);
+	if (!qda_user) {
+		qda_dbg(qdev, "Failed to allocate qda_user\n");
+		kfree(qda_file_priv);
+		return -ENOMEM;
+	}
+
+	file->driver_priv = qda_file_priv;
+	qda_file_priv->qda_user = qda_user;
+
+	qda_dbg(qdev, "Device opened successfully for PID %d\n", current->pid);
+
+	return 0;
+}
+
+static void qda_postclose(struct drm_device *dev, struct drm_file *file)
+{
+	struct qda_dev *qdev;
+	struct qda_file_priv *qda_file_priv;
+	struct qda_user *qda_user;
+
+	qdev = get_qdev_from_drm_device(dev);
+	if (!qdev || atomic_read(&qdev->removing)) {
+		qda_dbg(NULL, "Device unavailable or removing\n");
+		return;
+	}
+
+	qda_file_priv = (struct qda_file_priv *)file->driver_priv;
+	if (qda_file_priv) {
+		qda_user = qda_file_priv->qda_user;
+		if (qda_user)
+			free_qda_user(qda_user);
+
+		kfree(qda_file_priv);
+		file->driver_priv = NULL;
+	}
+
+	qda_dbg(qdev, "Device closed for PID %d\n", current->pid);
+}
+
 DEFINE_DRM_ACCEL_FOPS(qda_accel_fops);
 
 static struct drm_driver qda_drm_driver = {
 	.driver_features = DRIVER_COMPUTE_ACCEL,
 	.fops			= &qda_accel_fops,
+	.open			= qda_open,
+	.postclose		= qda_postclose,
 	.name = DRIVER_NAME,
 	.desc = "Qualcomm DSP Accelerator Driver",
 };
@@ -58,6 +174,7 @@ static void init_device_resources(struct qda_dev *qdev)
 
 	mutex_init(&qdev->lock);
 	atomic_set(&qdev->removing, 0);
+	atomic_set(&qdev->client_id_counter, 0);
 }
 
 static int init_memory_manager(struct qda_dev *qdev)
diff --git a/drivers/accel/qda/qda_drv.h b/drivers/accel/qda/qda_drv.h
index 2b80401a3741..e0ba37702a86 100644
--- a/drivers/accel/qda/qda_drv.h
+++ b/drivers/accel/qda/qda_drv.h
@@ -10,6 +10,7 @@
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/rpmsg.h>
+#include <linux/types.h>
 #include <linux/xarray.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
@@ -20,6 +21,33 @@
 /* Driver identification */
 #define DRIVER_NAME "qda"
 
+/**
+ * struct qda_file_priv - Per-process private data for DRM file
+ *
+ * This structure tracks per-process state for each open file descriptor.
+ * It maintains the IOMMU device assignment and links to the legacy qda_user
+ * structure for compatibility with existing code.
+ */
+struct qda_file_priv {
+	/* Process ID for tracking */
+	pid_t pid;
+	/* Pointer to qda_user structure for backward compatibility */
+	struct qda_user *qda_user;
+};
+
+/**
+ * struct qda_user - Per-user context for remote processor interaction
+ *
+ * This structure maintains per-user state for interactions with the
+ * remote processor, including memory mappings and pending operations.
+ */
+struct qda_user {
+	/* Unique client identifier */
+	u32 client_id;
+	/* Back-pointer to device structure */
+	struct qda_dev *qda_dev;
+};
+
 /**
  * struct qda_drm_priv - DRM device private data for QDA device
  *
@@ -52,6 +80,8 @@ struct qda_dev {
 	struct qda_drm_priv *drm_priv;
 	/* Flag indicating device removal in progress */
 	atomic_t removing;
+	/* Atomic counter for generating unique client IDs */
+	atomic_t client_id_counter;
 	/* Name of the DSP (e.g., "cdsp", "adsp") */
 	char dsp_name[16];
 	/* Compute context-bank (CB) child devices */

-- 
2.34.1