Messages in this thread | | | Date | Wed, 8 Aug 2007 09:47:48 +0100 | From | Alan Cox <> | Subject | Re: [PATCH] serial inter-character timeout usage with async io |
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> A Linux program is connected via serial port to some other serial device > using asynchronous I/O and the other serial device sends a 150 byte > sequence to the Linux program. The Linux program will receive 18 > intermediate SIGIOs (one for each 8-byte threshold interrupt generated > by the UART) followed by 1 final inter-character timeout (when the UART > FIFO contains the last 6 bytes). The program upon each SIGIO would > read() 8 bytes and do some parsing of the data buffer and realize that > the whole sequence had not yet been received. Repeat 17 more times in > this example.
That seems a particularly odd way to implement block I/O. Just use a thread for this and the VMIN/VTIME functionality in the n_tty layer - that is why it is there.
> I agree. However, the inter-character timeout is present (to the best of > my knowledge and google's) in all serial UARTs from the 16550A onward > (starting around 1994 and Windows 3.1). Before that, the IIR timeout
Almost all our drivers are not 16550A. A large part of the serial world is now USB and current PCs (especially laptops) often don't include any 16550A devices at all.
Your changes seem to be - hardware specific, not supportable by many devices, and designed to improve a particularly crazy way of handling the I/O in the first place. That doesn't make a good candidate for the upstream kernel.
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