Some Question About Polling I'm trying to understand the section _[13.2.1 polling[ I don't understand two parts in the link: 1. Is that the _["]4. The **control register** ... [."]_, which is mentioned above the _Figure 13.2_ , the same as _["]3. The host sets the command ready bit in the **command register** to ...[."]_? 2. _["]2. The host writes a byte of data into the **data-out** register, and ...[."]_ Why it's not _data-in_ register? How does Linux do _Polling_?

1. It seems the author has some particular device in mind, probably the parallel port, when writing this sentence, but doesn't mention it, so it sounds like it is a general description of device registers. You shouldn't worry about it, because as a general description it is useless.



The control register and command register is probably the same here.

2. It's data-out because this section talks about sending data. It should have mentioned that somewhere.