misc: fastrpc: Fix DSP capabilities request

The DSP capability request call expects 2 arguments. First is the
information about the total number of attributes to be copied from
DSP and second is the information about the buffer where the DSP
needs to copy the information. The current design is passing the
information about the size to be copied from DSP which would be
considered as a bad argument to the call by DSP causing a failure
suggesting the same. The second argument carries the information
about the buffer where the DSP needs to copy the capability
information and the size to be copied. As the first entry of
capability attribute is getting skipped, same should also be
considered while sending the information to DSP. Add changes to
pass proper arguments to DSP.

Fixes: 6c16fd8b ("misc: fastrpc: Add support to get DSP capabilities")
Cc: stable <stable@kernel.org>
Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240628114501.14310-2-srinivas.kandagatla@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/fastrpc.c

@@ -1693,14 +1693,19 @@ static int fastrpc_get_info_from_dsp(struct fastrpc_user *fl, uint32_t *dsp_attr
 {
 	struct fastrpc_invoke_args args[2] = { 0 };
 
-	/* Capability filled in userspace */
+	/*
+	 * Capability filled in userspace. This carries the information
+	 * about the remoteproc support which is fetched from the remoteproc
+	 * sysfs node by userspace.
+	 */
 	dsp_attr_buf[0] = 0;
+	dsp_attr_buf_len -= 1;
 
 	args[0].ptr = (u64)(uintptr_t)&dsp_attr_buf_len;
 	args[0].length = sizeof(dsp_attr_buf_len);
 	args[0].fd = -1;
 	args[1].ptr = (u64)(uintptr_t)&dsp_attr_buf[1];
-	args[1].length = dsp_attr_buf_len;
+	args[1].length = dsp_attr_buf_len * sizeof(u32);
 	args[1].fd = -1;
 	fl->pd = USER_PD;
 
@@ -1730,7 +1735,7 @@ static int fastrpc_get_info_from_kernel(struct fastrpc_ioctl_capability *cap,
 	if (!dsp_attributes)
 		return -ENOMEM;
 
-	err = fastrpc_get_info_from_dsp(fl, dsp_attributes, FASTRPC_MAX_DSP_ATTRIBUTES_LEN);
+	err = fastrpc_get_info_from_dsp(fl, dsp_attributes, FASTRPC_MAX_DSP_ATTRIBUTES);
 	if (err == DSP_UNSUPPORTED_API) {
 		dev_info(&cctx->rpdev->dev,
 			 "Warning: DSP capabilities not supported on domain: %d\n", domain);