Re: [PATCH v2 08/15] accel/qda: Add QUERY IOCTL and QDA UAPI header

On Tue, Aug 18, 2026 at 10:10:16AM +0530, Ekansh Gupta wrote:
> On 17-08-2026 12:28, Dmitry Baryshkov wrote:
> > On Mon, Aug 17, 2026 at 10:17:43AM +0530, Ekansh Gupta wrote:
> >> Introduce DRM_IOCTL_QDA_QUERY, a query IOCTL that lets user-space
> >> retrieve information about the DSP a given /dev/accel/accel* node
> >> represents.
> >>
> >> The IOCTL takes a query_type selector as input, so it can be extended
> >> to return additional parameters (capabilities, attributes) in the
> >> future without adding new IOCTLs: drm_ioctl() zero-extends the argument
> >> structure, so new fields can be appended to struct drm_qda_query as
> >> long as they go at the end. The first supported query,
> >> QDA_QUERY_DSP_NAME, returns the DSP domain name (e.g. "cdsp", "adsp").
> >>
> >> The UAPI header include/uapi/drm/qda_accel.h defines the command number,
> >> the DRM_IOWR IOCTL definition, the query_type values, and struct
> >> drm_qda_query. It follows the standard DRM UAPI conventions: fixed-width
> >> types, a C++ extern "C" guard, and GPL-2.0-only WITH Linux-syscall-note
> >> licensing.
> >>
> >> qda_ioctl_query() validates the reserved pad field, dispatches on
> >> query_type, and copies the DSP name from qda_dev.dsp_name into the
> >> user-supplied buffer with strscpy(). Unknown query types are rejected
> >> with -EINVAL.
> >>
> >> qda_drv.c registers the qda_ioctls[] table with the drm_driver so the
> >> DRM core dispatches DRM_IOCTL_QDA_QUERY to qda_ioctl_query().
> > 


> >> + */
> >> +#define DRM_IOCTL_QDA_QUERY		DRM_IOWR(DRM_COMMAND_BASE + DRM_QDA_QUERY, \
> >> +					 struct drm_qda_query)
> >> +
> >> +/* Query type definitions for drm_qda_query */
> >> +#define QDA_QUERY_DSP_NAME	1
> > 
> > Why is it necessary for the userspace?
> Currently the requirement is that on systems with multiple DSP domains,
> each is exposed as a separate /dev/accel/accelN node, the library must
> query the domain name to select the correct DSP to offload to and use
> other dependencies like shell etc.

Commit message.


-- 
With best wishes
Dmitry