Re: [PATCH v2 07/15] accel/qda: Add memory manager for CB devices

On Tue, Aug 18, 2026 at 10:03:56AM +0530, Ekansh Gupta wrote:
> On 17-08-2026 12:22, Dmitry Baryshkov wrote:
> > On Mon, Aug 17, 2026 at 10:17:42AM +0530, Ekansh Gupta wrote:
> >> Introduce the QDA memory manager (qda_memory_manager) to track the
> >> IOMMU devices that back each compute context bank (CB).
> >>
> >> Each CB device registered on the qda-compute-cb bus is wrapped in a
> >> qda_iommu_device descriptor recording the device pointer and its stream
> >> ID, and stored in the memory manager's registry. Later patches use this
> >> registry to resolve the IOMMU device a session should allocate from.
> >>
> >> The registry is a plain array sized to the number of
> >> "qcom,fastrpc-compute-cb" nodes present in the device tree: the RPMsg
> >> probe counts those nodes and passes the count to qda_init_device(),
> >> which allocates the array in qda_memory_manager_init(). The memory
> >> manager is created before CB devices are populated and destroyed after
> >> they are torn down, so no dangling descriptors remain.
> >>
> >> qda_cb_setup_device() is called immediately after a CB device is
> >> registered on the bus: it allocates the descriptor, registers it with
> >> the memory manager, and stores it as the CB device's driver data so
> >> that qda_destroy_cb_device() can unregister and free it during teardown.
> >>
> >> Assisted-by: Claude:claude-sonnet-5
> >> Signed-off-by: Ekansh Gupta <[email protected]>
> >> ---
> >> Changes in v2:
> >> - Replace the XArray with a plain array sized to the device tree's CB
> >>   node count instead of a fixed 16-entry table (Dmitry Baryshkov)
> >> - Fold the init_memory_manager()/cleanup_memory_manager() wrappers into
> >>   qda_init_device()/qda_deinit_device() (Dmitry Baryshkov)
> >> - Drop the pr_debug() calls (Dmitry Baryshkov)
> >> - Use goto labels to unwind probe failures instead of open-coding the
> >>   cleanup at each error site (Dmitry Baryshkov)
> >> ---
> >>  drivers/accel/qda/Makefile             |  1 +
> >>  drivers/accel/qda/qda_cb.c             | 39 ++++++++++++++
> >>  drivers/accel/qda/qda_drv.c            | 26 +++++++++
> >>  drivers/accel/qda/qda_drv.h            |  5 ++
> >>  drivers/accel/qda/qda_memory_manager.c | 98 ++++++++++++++++++++++++++++++++++
> >>  drivers/accel/qda/qda_memory_manager.h | 55 +++++++++++++++++++
> >>  drivers/accel/qda/qda_rpmsg.c          | 23 +++++++-
> >>  7 files changed, 246 insertions(+), 1 deletion(-)
> >>
> >> +
> >> +/**
> >> + * struct qda_memory_manager - Central memory management coordinator
> >> + *
> >> + * Coordinates memory management across multiple IOMMU devices. Maintains
> >> + * a registry of devices in an array sized to the number of context banks
> >> + * described in the device tree.
> >> + */
> >> +struct qda_memory_manager {
> >> +	/** @devices: Array storing registered IOMMU devices */
> >> +	struct qda_iommu_device **devices;
> >> +	/** @num_devices: Number of registered IOMMU devices */
> >> +	int num_devices;
> > 
> > What for? Is devices array to be looped up to num_devices or
> > max_devices?
> num_devices is to trace device registry with manager, it grows on
> register operation. I'll improve the comment.

If it's a loop counter during device registration, make it a loop
counter. Don't store useless data.


-- 
With best wishes
Dmitry