That "blob" is the closed source driver code that the Pi requires today. "In common with every other mobile graphics core, using the VideoCore IV 3D graphics core on the Pi requires a block of closed-source binary driver code (a 'blob') which talks to the hardware," Upton wrote. "Our existing open-source graphics drivers are a thin shim running on the ARM11, which talks to that blob via a communication driver in the Linux kernel. The lack of true open-source graphics drivers and documentation is widely acknowledged to be a significant problem for Linux on ARM, as it prevents users from fixing driver bugs, adding features and generally understanding what their hardware is doing."
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