34 lines
1.3 KiB
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34 lines
1.3 KiB
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=================
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Built-in firmware
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=================
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Firmware can be built-in to the kernel, this means building the firmware
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into vmlinux directly, to enable avoiding having to look for firmware from
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the filesystem. Instead, firmware can be looked for inside the kernel
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directly. You can enable built-in firmware using the kernel configuration
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options:
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* CONFIG_EXTRA_FIRMWARE
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* CONFIG_EXTRA_FIRMWARE_DIR
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There are a few reasons why you might want to consider building your firmware
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into the kernel with CONFIG_EXTRA_FIRMWARE:
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* Speed
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* Firmware is needed for accessing the boot device, and the user doesn't
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want to stuff the firmware into the boot initramfs.
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Even if you have these needs there are a few reasons why you may not be
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able to make use of built-in firmware:
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* Legalese - firmware is non-GPL compatible
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* Some firmware may be optional
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* Firmware upgrades are possible, therefore a new firmware would implicate
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a complete kernel rebuild.
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* Some firmware files may be really large in size. The remote-proc subsystem
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is an example subsystem which deals with these sorts of firmware
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* The firmware may need to be scraped out from some device specific location
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dynamically, an example is calibration data for for some WiFi chipsets. This
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calibration data can be unique per sold device.
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