[S] Change in flashrom[main]: serial: Fix sp_flush_incoming for serprog TCP connections

[Stanislav Ponomarev (Code Review)]

Attention is currently required from: Stanislav Ponomarev.

Hello Anastasia Klimchuk, build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/flashrom/+/79112?usp=email

to look at the new patch set (#3).

Change subject: serial: Fix sp_flush_incoming for serprog TCP connections
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serial: Fix sp_flush_incoming for serprog TCP connections

During the development of an esp32 serprog-compatible SPI programmer,
and implementation of the TCP over Wi-Fi for serprog,
I discovered that sp_flush_incoming() silently fails
if the underlying sp_fd descriptor is a TCP socket.

This patch adds a check for this case - tcflush returns ENOTTY,
meaning tcflush is not supported for not terminal objects,
in this case a fallback serialport_read_nonblock loop is used.

TESTED=esp32-serprog, TCP-over-WiFi mode, ~90% connection attempts fail to synchronize without patch; no synchronization issues with patch applied.

Signed-off-by: Stanislav Ponomarev

Change-Id: I9724a2fcd4a41dede2c15f83877efa6c3b0b7fae
---
M serial.c
1 file changed, 20 insertions(+), 2 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/12/79112/3