Re: [PATCH RFC 11/18] accel/qda: Add GEM_CREATE and GEM_MMAP_OFFSET IOCTLs

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

On 2/24/2026 4:09 AM, Dmitry Baryshkov wrote:
> On Tue, Feb 24, 2026 at 12:39:05AM +0530, Ekansh Gupta wrote:
>> Add two GEM-related IOCTLs for the QDA accelerator driver and hook
>> them into the DRM accel driver. DRM_IOCTL_QDA_GEM_CREATE allocates
>> a DMA-backed GEM buffer object via qda_gem_create_object() and
>> returns a GEM handle to userspace, while
>> DRM_IOCTL_QDA_GEM_MMAP_OFFSET returns a valid mmap offset for a
>> given GEM handle using drm_gem_create_mmap_offset() and the
>> vma_node in the GEM object.
>>
>> The QDA driver is updated to advertise DRIVER_GEM in its
>> driver_features, and the new IOCTLs are wired through the QDA
>> GEM and memory-manager backend. These IOCTLs allow userspace to
>> allocate buffers and map them into its address space as a first
>> step toward full compute buffer management and integration with
>> DSP workloads.
>>
>> Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
>> ---
>>  drivers/accel/qda/qda_drv.c   |  5 ++++-
>>  drivers/accel/qda/qda_gem.h   | 30 ++++++++++++++++++++++++++++++
>>  drivers/accel/qda/qda_ioctl.c | 35 +++++++++++++++++++++++++++++++++++
>>  include/uapi/drm/qda_accel.h  | 36 ++++++++++++++++++++++++++++++++++++
>>  4 files changed, 105 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/accel/qda/qda_drv.c b/drivers/accel/qda/qda_drv.c
>> index 19798359b14e..0dd0e2bb2c0f 100644
>> --- a/drivers/accel/qda/qda_drv.c
>> +++ b/drivers/accel/qda/qda_drv.c
>> @@ -12,6 +12,7 @@
>>  #include <drm/qda_accel.h>
>>  
>>  #include "qda_drv.h"
>> +#include "qda_gem.h"
>>  #include "qda_ioctl.h"
>>  #include "qda_rpmsg.h"
>>  
>> @@ -154,10 +155,12 @@ DEFINE_DRM_ACCEL_FOPS(qda_accel_fops);
>>  
>>  static const struct drm_ioctl_desc qda_ioctls[] = {
>>  	DRM_IOCTL_DEF_DRV(QDA_QUERY, qda_ioctl_query, 0),
>> +	DRM_IOCTL_DEF_DRV(QDA_GEM_CREATE, qda_ioctl_gem_create, 0),
>> +	DRM_IOCTL_DEF_DRV(QDA_GEM_MMAP_OFFSET, qda_ioctl_gem_mmap_offset, 0),
>>  };
>>  
>>  static struct drm_driver qda_drm_driver = {
>> -	.driver_features = DRIVER_COMPUTE_ACCEL,
>> +	.driver_features = DRIVER_GEM | DRIVER_COMPUTE_ACCEL,
>>  	.fops			= &qda_accel_fops,
>>  	.open			= qda_open,
>>  	.postclose		= qda_postclose,
>> diff --git a/drivers/accel/qda/qda_gem.h b/drivers/accel/qda/qda_gem.h
>> index caae9cda5363..cbd5d0a58fa4 100644
>> --- a/drivers/accel/qda/qda_gem.h
>> +++ b/drivers/accel/qda/qda_gem.h
>> @@ -47,6 +47,36 @@ struct drm_gem_object *qda_gem_create_object(struct drm_device *drm_dev,
>>  void qda_gem_free_object(struct drm_gem_object *gem_obj);
>>  int qda_gem_mmap_obj(struct drm_gem_object *gem_obj, struct vm_area_struct *vma);
>>  
>> +/*
>> + * GEM IOCTL handlers
>> + */
>> +
>> +/**
>> + * qda_ioctl_gem_create - Create a GEM buffer object
>> + * @dev: DRM device structure
>> + * @data: User-space data containing buffer creation parameters
>> + * @file_priv: DRM file private data
>> + *
>> + * This IOCTL handler creates a new GEM buffer object with the specified
>> + * size and returns a handle to the created buffer.
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +int qda_ioctl_gem_create(struct drm_device *dev, void *data, struct drm_file *file_priv);
>> +
>> +/**
>> + * qda_ioctl_gem_mmap_offset - Get mmap offset for a GEM buffer object
>> + * @dev: DRM device structure
>> + * @data: User-space data containing buffer handle and offset result
>> + * @file_priv: DRM file private data
>> + *
>> + * This IOCTL handler retrieves the mmap offset for a GEM buffer object,
>> + * which can be used to map the buffer into user-space memory.
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +int qda_ioctl_gem_mmap_offset(struct drm_device *dev, void *data, struct drm_file *file_priv);
>> +
>>  /*
>>   * Helper functions for GEM object allocation and cleanup
>>   * These are used internally and by the PRIME import code
>> diff --git a/drivers/accel/qda/qda_ioctl.c b/drivers/accel/qda/qda_ioctl.c
>> index 9fa73ec2dfce..ef3c9c691cb7 100644
>> --- a/drivers/accel/qda/qda_ioctl.c
>> +++ b/drivers/accel/qda/qda_ioctl.c
>> @@ -43,3 +43,38 @@ int qda_ioctl_query(struct drm_device *dev, void *data, struct drm_file *file_pr
>>  
>>  	return 0;
>>  }
>> +
>> +int qda_ioctl_gem_create(struct drm_device *dev, void *data, struct drm_file *file_priv)
>> +{
>> +	struct drm_qda_gem_create *args = data;
>> +	struct drm_gem_object *gem_obj;
>> +	struct qda_drm_priv *drm_priv;
>> +
>> +	drm_priv = get_drm_priv_from_device(dev);
>> +	if (!drm_priv || !drm_priv->iommu_mgr)
>> +		return -EINVAL;
>> +
>> +	gem_obj = qda_gem_create_object(dev, drm_priv->iommu_mgr, args->size, file_priv);
>> +	if (IS_ERR(gem_obj))
>> +		return PTR_ERR(gem_obj);
>> +
>> +	return qda_gem_create_handle(file_priv, gem_obj, &args->handle);
>> +}
>> +
>> +int qda_ioctl_gem_mmap_offset(struct drm_device *dev, void *data, struct drm_file *file_priv)
>> +{
>> +	struct drm_qda_gem_mmap_offset *args = data;
>> +	struct drm_gem_object *gem_obj;
>> +	int ret;
>> +
>> +	gem_obj = qda_gem_lookup_object(file_priv, args->handle);
>> +	if (IS_ERR(gem_obj))
>> +		return PTR_ERR(gem_obj);
>> +
>> +	ret = drm_gem_create_mmap_offset(gem_obj);
>> +	if (ret == 0)
>> +		args->offset = drm_vma_node_offset_addr(&gem_obj->vma_node);
>> +
>> +	drm_gem_object_put(gem_obj);
>> +	return ret;
>> +}
>> diff --git a/include/uapi/drm/qda_accel.h b/include/uapi/drm/qda_accel.h
>> index 0aad791c4832..ed24a7f5637e 100644
>> --- a/include/uapi/drm/qda_accel.h
>> +++ b/include/uapi/drm/qda_accel.h
>> @@ -19,6 +19,8 @@ extern "C" {
>>   * They are used with DRM_COMMAND_BASE to create the full IOCTL numbers.
>>   */
>>  #define DRM_QDA_QUERY	0x00
>> +#define DRM_QDA_GEM_CREATE		0x01
>> +#define DRM_QDA_GEM_MMAP_OFFSET	0x02
>>  /*
>>   * QDA IOCTL definitions
>>   *
>> @@ -27,6 +29,10 @@ extern "C" {
>>   * data structure and direction (read/write) for each IOCTL.
>>   */
>>  #define DRM_IOCTL_QDA_QUERY	DRM_IOR(DRM_COMMAND_BASE + DRM_QDA_QUERY, struct drm_qda_query)
>> +#define DRM_IOCTL_QDA_GEM_CREATE	DRM_IOWR(DRM_COMMAND_BASE + DRM_QDA_GEM_CREATE, \
>> +						 struct drm_qda_gem_create)
>> +#define DRM_IOCTL_QDA_GEM_MMAP_OFFSET	DRM_IOWR(DRM_COMMAND_BASE + DRM_QDA_GEM_MMAP_OFFSET, \
>> +						 struct drm_qda_gem_mmap_offset)
>>  
>>  /**
>>   * struct drm_qda_query - Device information query structure
>> @@ -40,6 +46,36 @@ struct drm_qda_query {
>>  	__u8 dsp_name[16];
>>  };
>>  
>> +/**
>> + * struct drm_qda_gem_create - GEM buffer object creation parameters
>> + * @size: Size of the GEM object to create in bytes (input)
>> + * @handle: Allocated GEM handle (output)
>> + *
>> + * This structure is used with DRM_IOCTL_QDA_GEM_CREATE to allocate
>> + * a new GEM buffer object.
>> + */
>> +struct drm_qda_gem_create {
>> +	__u32 handle;
>> +	__u32 pad;
>> +	__u64 size;
> If you put size before handle, you would not need padding.
ack
>
>> +};
>> +
>> +/**
>> + * struct drm_qda_gem_mmap_offset - GEM object mmap offset query
>> + * @handle: GEM handle (input)
>> + * @pad: Padding for 64-bit alignment
>> + * @offset: mmap offset for the GEM object (output)
>> + *
>> + * This structure is used with DRM_IOCTL_QDA_GEM_MMAP_OFFSET to retrieve
>> + * the mmap offset that can be used with mmap() to map the GEM object into
>> + * user space.
>> + */
>> +struct drm_qda_gem_mmap_offset {
>> +	__u32 handle;
>> +	__u32 pad;
>> +	__u64 offset;
> I'm really not a fan of the pad field in the middle of the structure.
ack
>
>> +};
>> +
>>  #if defined(__cplusplus)
>>  }
>>  #endif
>>
>> -- 
>> 2.34.1
>>