Hi, During the review process of my 8250 nbcon series, Petr Mladek mentioned [0] that it was odd that the console driver clears UART_LSR_DR from @read_status_mask but never sets it. Since there is literally zero documentation on the driver-specific fields @read_status_mask and @ignore_status_mask, I embarked on a journey to figure out what these fields are for and how they are supposed to be used. My quest took me back to Linux 1.1.60, where there was the first significant change in the purpose of these fields. That purpose was then reverted in Linux 2.1.8, but some of the pieces were forgotten. Over the years it seems no one really noticed as these bogus pieces hung around and were even expanded upon. And yes, I uncovered a subtle bug that has been around longer than git. This series cleans up the usage for the @read_status_mask field and adds some documentation so that future developers will know what this field is actually for. And the series also fixes the subtle bug. Note that since the 8250 was the original serial driver and was copy/pasted as a basis for many later serial drivers, the issue may exist in other drivers as well. [0] https://lore.kernel.org/lkml/ZyuOX4VVbfAFhMfV@xxxxxxxxxxxxxxx John Ogness (4): serial: 8250: Use @ier bits to determine if Rx is stopped serial: 8250: Do not set UART_LSR_THRE in @read_status_mask serial: 8250: Never adjust UART_LSR_DR in @read_status_mask serial: 8250: Explain the role of @read_status_mask drivers/tty/serial/8250/8250_core.c | 1 - drivers/tty/serial/8250/8250_omap.c | 9 +++++++-- drivers/tty/serial/8250/8250_port.c | 11 ++++++++--- 3 files changed, 15 insertions(+), 6 deletions(-) base-commit: 30691a59c85c48575b04e849f675660fd8060cad -- 2.39.5
