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

[Dmitry Baryshkov]

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@xxxxxxxxxxxxxxxx>
> ---
>  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.

>  
>  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.

> +	.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?

> +
> +	*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
> 

-- 
With best wishes
Dmitry