On 1/6/2026 8:21 AM, Dmitry Baryshkov wrote:
> On Tue, Dec 30, 2025 at 04:32:25PM +0530, Ekansh Gupta wrote:
>> Currently, FastRPC only supports mapping buffers allocated by the
>> kernel. This limits flexibility for applications that allocate memory
>> in userspace using rpcmem or DMABUF and need to share it with the DSP.
> Hmm, for DMABUF we need _import_ support rather than support for mapping
> of userspace-allocated buffers.
>
>> Add support for mapping and unmapping userspace-allocated buffers to
>> the DSP through SMMU. This includes handling map requests for rpcmem
>> and DMABUF-backed memory and providing corresponding unmap
>> functionality.
> For me this definitely looks like a step back. For drm/accel we are
> going to have GEM-managed buffers only. Why do we need to handle
> userspace-allocated buffers here?
That's correct, GEM-PRIME will handle it properly. Here, the reason to add this
change is to enable routing of DSP logs to HLOS which is done by using a shared
buffer between userspace process and DSP PD. The buffer can be allocated from
both fastrpc driver's DMA-BUF or DMABUF heap(eg. system heap).
So this shared buffer is getting mapped to both process's IOMMU device and DSP
PD
with this change.
>
>> Signed-off-by: Ekansh Gupta <[email protected]>
>> ---
>> drivers/misc/fastrpc.c | 97 +++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 86 insertions(+), 11 deletions(-)
>>
>> @@ -1989,25 +2020,69 @@ static int fastrpc_req_buf_alloc(struct fastrpc_user
>> *fl,
>> return err;
>> }
>>
>> -static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
>> +static int fastrpc_req_map_create(struct fastrpc_user *fl,
>> + struct fastrpc_req_mmap req,
>> + char __user *argp)
>> {
>> - struct fastrpc_req_mmap req;
>> + struct fastrpc_map *map = NULL;
>> + struct device *dev = fl->sctx->dev;
>> + u64 raddr = 0;
>> int err;
>>
>> - if (copy_from_user(&req, argp, sizeof(req)))
>> - return -EFAULT;
>> + err = fastrpc_map_create(fl, req.fd, req.size, 0, &map);
>> + if (err) {
>> + dev_err(dev, "failed to map buffer, fd = %d\n", req.fd);
>> + return err;
>> + }
>> +
>> + err = fastrpc_req_map_dsp(fl, map->phys, map->size, req.flags,
>> + req.vaddrin, &raddr);
>> + if (err)
>> + goto err_invoke;
>>
>> - if (req.flags != ADSP_MMAP_ADD_PAGES && req.flags !=
>> ADSP_MMAP_REMOTE_HEAP_ADDR) {
>> - dev_err(fl->sctx->dev, "flag not supported 0x%x\n", req.flags);
>> + /* update the buffer to be able to deallocate the memory on the DSP */
>> + map->raddr = (u64)raddr;
> Which type are you converting? And why?
I'll drop this.
>
>>
>> - return -EINVAL;
>> + /* let the client know the address to use */
>> + req.vaddrout = raddr;
>> + dev_dbg(dev, "mmap OK: raddr=%p [len=0x%08llx]\n",
>> + (void *)(unsigned long)map->raddr, map->size);
>> +
>> + if (copy_to_user(argp, &req, sizeof(req))) {
>> + err = -EFAULT;
>> + goto err_copy;
>> }
>>
>> - err = fastrpc_req_buf_alloc(fl, req, argp);
>> + return 0;
>> +err_copy:
>> + fastrpc_req_munmap_dsp(fl, map->raddr, map->size);
>> +err_invoke:
>> + fastrpc_map_put(map);
>>
>> return err;
>> }
>>
>> +static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
>> +{
>> + struct fastrpc_req_mmap req;
>> + int err;
>> +
>> + if (copy_from_user(&req, argp, sizeof(req)))
>> + return -EFAULT;
>> +
>> + if ((req.flags == ADSP_MMAP_ADD_PAGES ||
>> + req.flags == ADSP_MMAP_REMOTE_HEAP_ADDR)) {
> Side note: why are these flags not defined in the uABI header?
Ack. These should be part of uABI. I'll create a separate patch for this.
>
>> + err = fastrpc_req_buf_alloc(fl, req, argp);
>> + if (err)
>> + return err;
