尤其要小心关注你的供应商所使用的上游技术，以及你的客户所使用的的下游技术，并弄清楚它们是如何工作到一起的。
Take an especially careful look at both the upstream technologies used by your suppliers and the downstream technologies used by your customers and how they work together.
令人开心的是：由于GCC使用的是GPL许可，它自带了全部源代码，分为上游版本和供应商补丁。
What makes this amusing, of course, is that since GCC is under the GPL, it is shipped with complete source code, broken down into upstream versions and vendor patches.
供应商希望利用自己的修改而无需提供参考内核，必须已经为他们的硬件驱动程序在上游Linux内核中。
Vendors wishing to use the reference kernel without supplying their own adaptations, must already have drivers for their hardware included in the upstream Linux kernel.
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