Re: [PATCH RFC 09/18] accel/qda: Add QUERY IOCTL and basic QDA UAPI header

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

On 2/24/2026 3:54 AM, Dmitry Baryshkov wrote:
> On Tue, Feb 24, 2026 at 12:39:03AM +0530, Ekansh Gupta wrote:
>> Introduce a basic UAPI for the QDA accelerator driver along with a
>> DRM IOCTL handler to query DSP device identity. A new UAPI header
>> include/uapi/drm/qda_accel.h defines DRM_QDA_QUERY, the corresponding
>> DRM_IOCTL_QDA_QUERY command, and struct drm_qda_query, which contains
>> a DSP name string.
>>
>> On the kernel side, qda_ioctl_query() validates the per-file context,
>> resolves the qda_dev instance from dev->dev_private, and copies the
>> DSP name from qdev->dsp_name into the query structure. The new
>> qda_ioctls[] table wires this IOCTL into the QDA DRM driver so
>> userspace can call it through the standard DRM command interface.
>>
>> This IOCTL provides a simple and stable way for userspace to discover
>> which DSP a given QDA device node represents and serves as the first
>> building block for a richer QDA UAPI in subsequent patches.
>>
>> Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
>> ---
>>  drivers/accel/qda/Makefile    |  1 +
>>  drivers/accel/qda/qda_drv.c   |  9 +++++++++
>>  drivers/accel/qda/qda_ioctl.c | 45 +++++++++++++++++++++++++++++++++++++++++
>>  drivers/accel/qda/qda_ioctl.h | 26 ++++++++++++++++++++++++
>>  include/uapi/drm/qda_accel.h  | 47 +++++++++++++++++++++++++++++++++++++++++++
>>  5 files changed, 128 insertions(+)
>>
>> diff --git a/drivers/accel/qda/Makefile b/drivers/accel/qda/Makefile
>> index 7e96ddc40a24..f547398e1a72 100644
>> --- a/drivers/accel/qda/Makefile
>> +++ b/drivers/accel/qda/Makefile
>> @@ -10,5 +10,6 @@ qda-y := \
>>  	qda_rpmsg.o \
>>  	qda_cb.o \
>>  	qda_memory_manager.o \
>> +	qda_ioctl.o \
> Keep the list sorted, please.
ack
>
>>  
>>  obj-$(CONFIG_DRM_ACCEL_QDA_COMPUTE_BUS) += qda_compute_bus.o
>> diff --git a/drivers/accel/qda/qda_drv.c b/drivers/accel/qda/qda_drv.c
>> index bf95fc782cf8..86758a9cd982 100644
>> --- a/drivers/accel/qda/qda_drv.c
>> +++ b/drivers/accel/qda/qda_drv.c
>> @@ -9,7 +9,10 @@
>>  #include <drm/drm_file.h>
>>  #include <drm/drm_gem.h>
>>  #include <drm/drm_ioctl.h>
>> +#include <drm/qda_accel.h>
>> +
>>  #include "qda_drv.h"
>> +#include "qda_ioctl.h"
>>  #include "qda_rpmsg.h"
>>  
>>  static struct qda_drm_priv *get_drm_priv_from_device(struct drm_device *dev)
>> @@ -128,11 +131,17 @@ static void qda_postclose(struct drm_device *dev, struct drm_file *file)
>>  
>>  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),
>> +};
>> +
>>  static struct drm_driver qda_drm_driver = {
>>  	.driver_features = DRIVER_COMPUTE_ACCEL,
>>  	.fops			= &qda_accel_fops,
>>  	.open			= qda_open,
>>  	.postclose		= qda_postclose,
>> +	.ioctls = qda_ioctls,
> Please select one style. Either you indent all assignments or you don't.
ack
>
>> +	.num_ioctls = ARRAY_SIZE(qda_ioctls),
>>  	.name = DRIVER_NAME,
>>  	.desc = "Qualcomm DSP Accelerator Driver",
>>  };
>> diff --git a/drivers/accel/qda/qda_ioctl.c b/drivers/accel/qda/qda_ioctl.c
>> new file mode 100644
>> index 000000000000..9fa73ec2dfce
>> --- /dev/null
>> +++ b/drivers/accel/qda/qda_ioctl.c
>> @@ -0,0 +1,45 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
>> +#include <drm/drm_ioctl.h>
>> +#include <drm/drm_gem.h>
>> +#include <drm/qda_accel.h>
>> +#include "qda_drv.h"
>> +#include "qda_ioctl.h"
>> +
>> +static int qda_validate_and_get_context(struct drm_device *dev, struct drm_file *file_priv,
>> +					struct qda_dev **qdev, struct qda_user **qda_user)
>> +{
>> +	struct qda_drm_priv *drm_priv = dev->dev_private;
>> +	struct qda_file_priv *qda_file_priv;
>> +
>> +	if (!drm_priv)
>> +		return -EINVAL;
>> +
>> +	*qdev = drm_priv->qdev;
>> +	if (!*qdev)
>> +		return -EINVAL;
> Can this actually happen or is it (un)wishful thinking?
>
>> +
>> +	qda_file_priv = (struct qda_file_priv *)file_priv->driver_priv;
>> +	if (!qda_file_priv || !qda_file_priv->qda_user)
>> +		return -EINVAL;
> What are you protecting against?
The intention for all these checks are to ensure channel is properly initialized before any
request is queued for any specific channel, I'll update the checks based on the current
initialization ordering.
>
>> +
>> +	*qda_user = qda_file_priv->qda_user;
>> +
>> +	return 0;
>> +}
>> +
>> +int qda_ioctl_query(struct drm_device *dev, void *data, struct drm_file *file_priv)
>> +{
>> +	struct qda_dev *qdev;
>> +	struct qda_user *qda_user;
>> +	struct drm_qda_query *args = data;
>> +	int ret;
>> +
>> +	ret = qda_validate_and_get_context(dev, file_priv, &qdev, &qda_user);
>> +	if (ret)
>> +		return ret;
>> +
>> +	strscpy(args->dsp_name, qdev->dsp_name, sizeof(args->dsp_name));
>> +
>> +	return 0;
>> +}
>> diff --git a/drivers/accel/qda/qda_ioctl.h b/drivers/accel/qda/qda_ioctl.h
>> new file mode 100644
>> index 000000000000..6bf3bcd28c0e
>> --- /dev/null
>> +++ b/drivers/accel/qda/qda_ioctl.h
>> @@ -0,0 +1,26 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
>> + */
>> +
>> +#ifndef _QDA_IOCTL_H
>> +#define _QDA_IOCTL_H
>> +
>> +#include <linux/types.h>
>> +#include <linux/kernel.h>
>> +#include <drm/drm_ioctl.h>
>> +#include "qda_drv.h"
>> +
>> +/**
>> + * qda_ioctl_query - Query DSP device information and capabilities
>> + * @dev: DRM device structure
>> + * @data: User-space data containing query parameters and results
>> + * @file_priv: DRM file private data
>> + *
>> + * This IOCTL handler queries information about the DSP device.
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +int qda_ioctl_query(struct drm_device *dev, void *data, struct drm_file *file_priv);
>> +
>> +#endif /* _QDA_IOCTL_H */
>> diff --git a/include/uapi/drm/qda_accel.h b/include/uapi/drm/qda_accel.h
>> new file mode 100644
>> index 000000000000..0aad791c4832
>> --- /dev/null
>> +++ b/include/uapi/drm/qda_accel.h
>> @@ -0,0 +1,47 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
>> +/*
>> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
>> + */
>> +
>> +#ifndef __QDA_ACCEL_H__
>> +#define __QDA_ACCEL_H__
>> +
>> +#include "drm.h"
>> +
>> +#if defined(__cplusplus)
>> +extern "C" {
>> +#endif
>> +
>> +/*
>> + * QDA IOCTL command numbers
>> + *
>> + * These define the command numbers for QDA-specific IOCTLs.
>> + * They are used with DRM_COMMAND_BASE to create the full IOCTL numbers.
>> + */
>> +#define DRM_QDA_QUERY	0x00
>> +/*
>> + * QDA IOCTL definitions
>> + *
>> + * These macros define the actual IOCTL numbers used by userspace applications.
>> + * They combine the command numbers with DRM_COMMAND_BASE and specify the
>> + * 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)
>> +
>> +/**
>> + * struct drm_qda_query - Device information query structure
>> + * @dsp_name: Name of DSP (e.g., "adsp", "cdsp", "cdsp1", "gdsp0", "gdsp1")
>> + *
>> + * This structure is used with DRM_IOCTL_QDA_QUERY to query device type,
>> + * allowing userspace to identify which DSP a device node represents. The
>> + * kernel provides the DSP name directly as a null-terminated string.
>> + */
>> +struct drm_qda_query {
>> +	__u8 dsp_name[16];
>> +};
>> +
>> +#if defined(__cplusplus)
>> +}
>> +#endif
>> +
>> +#endif /* __QDA_ACCEL_H__ */
>>
>> -- 
>> 2.34.1
>>