fwctl/bnxt_fwctl: Add documentation entries

Add bnxt_fwctl to the driver and fwctl documentation pages.

Link: https://patch.msgid.link/r/20260314151605.932749-6-pavan.chebbi@broadcom.com
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

3 files changed, 76 insertions, 0 deletions

diff --git a/Documentation/userspace-api/fwctl/bnxt_fwctl.rst b/Documentation/userspace-api/fwctl/bnxt_fwctl.rst
new file mode 100644
index 000000000000..97c9b095cf21
--- /dev/null
+++ b/Documentation/userspace-api/fwctl/bnxt_fwctl.rst
@@ -0,0 +1,74 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+fwctl bnxt driver
+=================
+
+:Author: Pavan Chebbi
+
+Overview
+========
+
+BNXT driver makes a fwctl service available through an auxiliary_device.
+The bnxt_fwctl driver binds to this device and registers itself with the
+fwctl subsystem.
+
+The bnxt_fwctl driver is agnostic to the device firmware internals. It
+uses the Upper Layer Protocol (ULP) conduit provided by bnxt to send
+HardWare Resource Manager (HWRM) commands to firmware.
+
+These commands can query or change firmware driven device configurations
+and read/write registers that are useful for debugging.
+
+bnxt_fwctl User API
+===================
+
+Each RPC request contains the HWRM input structure in the fwctl_rpc
+'in' buffer while 'out' will contain the response.
+
+A typical user application can send a FWCTL_INFO command using ioctl()
+to discover bnxt_fwctl's RPC capabilities as shown below:
+
+        ioctl(fd, FWCTL_INFO, &fwctl_info_msg);
+
+where fwctl_info_msg (of type struct fwctl_info) describes bnxt_info_msg
+(of type struct fwctl_info_bnxt). fwctl_info_msg is set up as follows:
+
+        size = sizeof(struct fwctl_info);
+        flags = 0;
+        device_data_len = sizeof(bnxt_info_msg);
+        out_device_data = (__aligned_u64)&bnxt_info_msg;
+
+The uctx_caps of bnxt_info_msg represents the capabilities as described
+in fwctl_bnxt_commands of include/uapi/fwctl/bnxt.h
+
+The FW RPC itself, FWCTL_RPC can be sent using ioctl() as:
+
+        ioctl(fd, FWCTL_RPC, &fwctl_rpc_msg);
+
+where fwctl_rpc_msg (of type struct fwctl_rpc) carries the HWRM command
+in its 'in' buffer. The HWRM input structures are described in
+include/linux/bnxt/hsi.h. An example for HWRM_VER_GET is shown below:
+
+        struct hwrm_ver_get_output resp;
+        struct fwctl_rpc fwctl_rpc_msg;
+        struct hwrm_ver_get_input req;
+
+        req.req_type = HWRM_VER_GET;
+        req.hwrm_intf_maj = HWRM_VERSION_MAJOR;
+        req.hwrm_intf_min = HWRM_VERSION_MINOR;
+        req.hwrm_intf_upd = HWRM_VERSION_UPDATE;
+        req.cmpl_ring = -1;
+        req.target_id = -1;
+
+        fwctl_rpc_msg.size = sizeof(struct fwctl_rpc);
+        fwctl_rpc_msg.scope = FWCTL_RPC_DEBUG_READ_ONLY;
+        fwctl_rpc_msg.in_len = sizeof(req);
+        fwctl_rpc_msg.out_len = sizeof(resp);
+        fwctl_rpc_msg.in = (__aligned_u64)&req;
+        fwctl_rpc_msg.out = (__aligned_u64)&resp;
+
+An example python3 program that can exercise this interface can be found in
+the following git repository:
+
+https://github.com/Broadcom/fwctl-tools
diff --git a/Documentation/userspace-api/fwctl/fwctl.rst b/Documentation/userspace-api/fwctl/fwctl.rst
index a74eab8d14c6..826817bfd54d 100644
--- a/Documentation/userspace-api/fwctl/fwctl.rst
+++ b/Documentation/userspace-api/fwctl/fwctl.rst
@@ -148,6 +148,7 @@ area resulting in clashes will be resolved in favour of a kernel implementation.
 fwctl User API
 ==============
 
+.. kernel-doc:: include/uapi/fwctl/bnxt.h
 .. kernel-doc:: include/uapi/fwctl/fwctl.h
 .. kernel-doc:: include/uapi/fwctl/mlx5.h
 .. kernel-doc:: include/uapi/fwctl/pds.h
diff --git a/Documentation/userspace-api/fwctl/index.rst b/Documentation/userspace-api/fwctl/index.rst
index 316ac456ad3b..8062f7629654 100644
--- a/Documentation/userspace-api/fwctl/index.rst
+++ b/Documentation/userspace-api/fwctl/index.rst
@@ -10,5 +10,6 @@ to securely construct and execute RPCs inside device firmware.
    :maxdepth: 1
 
    fwctl
+   bnxt_fwctl
    fwctl-cxl
    pds_fwctl