serial: implement receive FIFO flush via FCR#103
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To be tested by @cperciva |
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@cperciva have you had time to test this patch? |
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CI failures are unrelated it seeems:
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The FIFO Control Register (FCR) controls the behavior of the receive and transmit FIFO buffers of the device. The current implementation does not emulate this register, as FIFO buffers are always enabled. However, there are two bits in this register that control flushing of said FIFOS. The transmission FIFO is already flushed by the current implementation on every write, but the receive FIFO is not. This is problematic, as some driver implementations (e.g. FreeBSD's) rely on being able to clear this buffer via the corresponding bit. Implement the correct behavior when a driver sets this bit by clearing `in_buffer`. Since there is no more data in the receive FIFO, the data-ready bit in the Line Status Register (LSR) must be cleared as well, in case it was set. Fixes: rust-vmm#83 Signed-off-by: Carlos López <carlos.lopezr4096@gmail.com>
Add a test that checks that flushing the receive FIFO results in the correct behavior, i.e. `in_buffer` is cleared. Signed-off-by: Carlos López <carlos.lopezr4096@gmail.com>
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Summary of the PR
The FIFO Control Register (FCR) controls the behavior of the receive and transmit FIFO buffers of the device. The current implementation does not emulate this register, as FIFO buffers are always enabled. However, there are two bits in this register that control flushing of said FIFOS. The transmission FIFO is already flushed by the current implementation on every write, but the receive FIFO is not. This is problematic, as some driver implementations (e.g. FreeBSD's) rely on being able to clear this buffer via the corresponding bit.
Implement the correct behavior when a driver sets this bit by clearing
in_buffer. Since there is no more data in the receive FIFO, the data-ready bit in the Line Status Register (LSR) must be cleared as well, in case it was set.Add a test for this new feature as well.
Fixes #83
Requirements
git commit -s), and the commitmessage has max 60 characters for the summary and max 75 characters for each
description line.
test.
Release" section of CHANGELOG.md (if no such section exists, please create one).
N/AAny newly addedunsafecode is properly documented.