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Currently the firmware loader only exposes one silent path for querying optional firmware, and that is firmware_request_direct(). This function also disables the sysfs fallback mechanism, which might not always be the desired behaviour [0]. This patch introduces a variations of request_firmware() that enable the caller to disable the undesired warning messages but enables the sysfs fallback mechanism. This is equivalent to adding FW_OPT_NO_WARN to the old behaviour. [0]: https://git.kernel.org/linus/c0cc00f250e1 Signed-off-by: Andres Rodriguez <andresx7@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Luis R. Rodriguez <mcgrof@kernel.org> [mcgrof: used the old API calls as the full rename is not done yet, and add the caller for when FW_LOADER is disabled, enhance documentation ] Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
76 lines
2.6 KiB
ReStructuredText
76 lines
2.6 KiB
ReStructuredText
====================
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request_firmware API
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====================
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You would typically load firmware and then load it into your device somehow.
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The typical firmware work flow is reflected below::
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if(request_firmware(&fw_entry, $FIRMWARE, device) == 0)
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copy_fw_to_device(fw_entry->data, fw_entry->size);
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release_firmware(fw_entry);
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Synchronous firmware requests
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=============================
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Synchronous firmware requests will wait until the firmware is found or until
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an error is returned.
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request_firmware
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----------------
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.. kernel-doc:: drivers/base/firmware_loader/main.c
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:functions: request_firmware
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firmware_request_nowarn
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-----------------------
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.. kernel-doc:: drivers/base/firmware_loader/main.c
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:functions: firmware_request_nowarn
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request_firmware_direct
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-----------------------
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.. kernel-doc:: drivers/base/firmware_loader/main.c
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:functions: request_firmware_direct
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request_firmware_into_buf
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-------------------------
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.. kernel-doc:: drivers/base/firmware_loader/main.c
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:functions: request_firmware_into_buf
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Asynchronous firmware requests
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==============================
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Asynchronous firmware requests allow driver code to not have to wait
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until the firmware or an error is returned. Function callbacks are
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provided so that when the firmware or an error is found the driver is
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informed through the callback. request_firmware_nowait() cannot be called
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in atomic contexts.
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request_firmware_nowait
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-----------------------
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.. kernel-doc:: drivers/base/firmware_loader/main.c
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:functions: request_firmware_nowait
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Special optimizations on reboot
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===============================
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Some devices have an optimization in place to enable the firmware to be
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retained during system reboot. When such optimizations are used the driver
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author must ensure the firmware is still available on resume from suspend,
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this can be done with firmware_request_cache() instead of requesting for the
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firmware to be loaded.
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firmware_request_cache()
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------------------------
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.. kernel-doc:: drivers/base/firmware_loader/main.c
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:functions: firmware_request_cache
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request firmware API expected driver use
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========================================
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Once an API call returns you process the firmware and then release the
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firmware. For example if you used request_firmware() and it returns,
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the driver has the firmware image accessible in fw_entry->{data,size}.
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If something went wrong request_firmware() returns non-zero and fw_entry
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is set to NULL. Once your driver is done with processing the firmware it
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can call call release_firmware(fw_entry) to release the firmware image
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and any related resource.
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