Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 75 insertions, 0 deletions

diff --git a/Documentation/driver-api/firmware/request_firmware.rst b/Documentation/driver-api/firmware/request_firmware.rst
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+====================
+request_firmware API
+====================
+
+You would typically load firmware and then load it into your device somehow.
+The typical firmware work flow is reflected below::
+
+	 if(request_firmware(&fw_entry, $FIRMWARE, device) == 0)
+                copy_fw_to_device(fw_entry->data, fw_entry->size);
+	 release_firmware(fw_entry);
+
+Synchronous firmware requests
+=============================
+
+Synchronous firmware requests will wait until the firmware is found or until
+an error is returned.
+
+request_firmware
+----------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: request_firmware
+
+firmware_request_nowarn
+-----------------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: firmware_request_nowarn
+
+request_firmware_direct
+-----------------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: request_firmware_direct
+
+request_firmware_into_buf
+-------------------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: request_firmware_into_buf
+
+Asynchronous firmware requests
+==============================
+
+Asynchronous firmware requests allow driver code to not have to wait
+until the firmware or an error is returned. Function callbacks are
+provided so that when the firmware or an error is found the driver is
+informed through the callback. request_firmware_nowait() cannot be called
+in atomic contexts.
+
+request_firmware_nowait
+-----------------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: request_firmware_nowait
+
+Special optimizations on reboot
+===============================
+
+Some devices have an optimization in place to enable the firmware to be
+retained during system reboot. When such optimizations are used the driver
+author must ensure the firmware is still available on resume from suspend,
+this can be done with firmware_request_cache() instead of requesting for the
+firmware to be loaded.
+
+firmware_request_cache()
+------------------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: firmware_request_cache
+
+request firmware API expected driver use
+========================================
+
+Once an API call returns you process the firmware and then release the
+firmware. For example if you used request_firmware() and it returns,
+the driver has the firmware image accessible in fw_entry->{data,size}.
+If something went wrong request_firmware() returns non-zero and fw_entry
+is set to NULL. Once your driver is done with processing the firmware it
+can call call release_firmware(fw_entry) to release the firmware image
+and any related resource.