kernel.git/drivers/tty/n_tty.c, branch linux-5.13.y

tty: create internal tty.h file

2021-04-15T08:22:17Z

There are a number of functions and #defines in include/linux/tty.h that do not belong there as they are private to the tty core code. Create an initial drivers/tty/tty.h file and copy the odd "tty logging" macros into it to seed the file with some initial things that we know nothing outside of the tty core should be calling. Cc: Tetsuo Handa Cc: Jiri Slaby Link: https://lore.kernel.org/r/20210408125134.3016837-2-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty, set tty_ldisc_ops::owner

2021-03-10T08:34:06Z

Set tty_ldisc_ops::owner to THIS_MODULE. This has no effect currently as n_tty cannot be built as a module. If someone ever tries to modularize tty, we wouldn't manage module's reference count as in other ldiscs. So fix this just in case. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210302062214.29627-9-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

tty: remove TTY_LDISC_MAGIC

2021-03-10T08:34:06Z

First, it is never checked. Second, use of it as a debugging aid is at least questionable. With the current tools, I don't think anyone used this kind of thing for debugging purposes for years. On the top of that, e.g. serdev does not set this field of tty_ldisc_ops at all. So get rid of this legacy. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210302062214.29627-8-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

Merge tag 'tty-5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2021-02-21T05:28:04Z

Pull tty/serial driver updates from Greg KH: "Here is the big set of tty/serial driver changes for 5.12-rc1. Nothing huge, just lots of good cleanups and additions: - n_tty line discipline cleanups - vt core cleanups and reworks to make the code more "modern" - stm32 driver additions - tty led support added to the tty core and led layer - minor serial driver fixups and additions All of these have been in linux-next for a while with no reported issues" * tag 'tty-5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (54 commits) serial: core: Remove BUG_ON(in_interrupt()) check vt_ioctl: Remove in_interrupt() check dt-bindings: serial: imx: Switch to my personal address vt: keyboard, use new API for keyboard_tasklet serial: stm32: improve platform_get_irq condition handling in init_port serial: ifx6x60: Remove driver for deprecated platform tty: fix up iterate_tty_read() EOVERFLOW handling tty: fix up hung_up_tty_read() conversion tty: fix up hung_up_tty_write() conversion tty: teach the n_tty ICANON case about the new "cookie continuations" too tty: teach n_tty line discipline about the new "cookie continuations" tty: clean up legacy leftovers from n_tty line discipline tty: implement read_iter tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer serial: remove sirf prima/atlas driver serial: mxs-auart: Remove serial: mxs-auart: Remove serial_mxs_probe_dt() serial: fsl_lpuart: Use of_device_get_match_data() dt-bindings: serial: renesas,hscif: Add r8a779a0 support tty: serial: Drop unused efm32 serial driver ...

Commit 9bb48c82aced ("tty: implement write_iter") converted the tty

2021-01-25T20:08:07Z

layer to use write_iter. Fix the redirected_tty_write declaration also in n_tty and change the comparisons to use write_iter instead of write. [ Also moved the declaration of redirected_tty_write() to the proper location in a header file. The reason for the bug was the bogus extern declaration in n_tty.c silently not matching the changed definition in tty_io.c, and because it wasn't in a shared header file, there was no cross-checking of the declaration. Sami noticed because Clang's Control Flow Integrity checking ended up incidentally noticing the inconsistent declaration. - Linus ] Fixes: 9bb48c82aced ("tty: implement write_iter") Signed-off-by: Sami Tolvanen Signed-off-by: Linus Torvalds

Merge branch 'tty-splice' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into tty-next

2021-01-21T08:40:55Z

Fixes both the "splice/sendfile to a tty" and "splice/sendfile from a tty" regression from 5.10. * 'tty-splice' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux: tty: teach the n_tty ICANON case about the new "cookie continuations" too tty: teach n_tty line discipline about the new "cookie continuations" tty: clean up legacy leftovers from n_tty line discipline tty: implement read_iter tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer tty: implement write_iter

tty: teach the n_tty ICANON case about the new "cookie continuations" too

2021-01-21T00:48:49Z

The ICANON case is a bit messy, since it has to look for the line ending, and has special code to then suppress line ending characters if they match the __DISABLED_CHAR. So it actually looks up the line ending even past the point where it knows it won't copy it to the result buffer. That said, apart from all those odd legacy N_TTY ICANON cases, the actual "should we continue copying" logic isn't really all that complicated or different from the non-canon case. In fact, the lack of "wait for at least N characters" arguably makes the repeat case slightly simpler. It really just boils down to "there's more of the line to be copied". So add the necessarily trivial logic, and now the N_TTY case will give long result lines even when in canon mode. Signed-off-by: Linus Torvalds

tty: teach n_tty line discipline about the new "cookie continuations"

2021-01-21T00:48:48Z

With the conversion to do the tty ldisc read operations in small chunks, the n_tty line discipline became noticeably slower for throughput oriented loads, because rather than read things in up to 2kB chunks, it would return at most 64 bytes per read() system call. The cost is mainly all in the "do system calls over and over", not really in the new "copy to an extra kernel buffer". This can be fixed by teaching the n_tty line discipline about the "cookie continuation" model, which the chunking code supports because things like hdlc need to be able to handle packets up to 64kB in size. Doing that doesn't just get us back to the old performace, but to much better performance: my stupid "copy 10MB of data over a pty" test program is now almost twice as fast as it used to be (going down from 0.1s to 0.054s). This is entirely because it now creates maximal chunks (which happens to be "one byte less than one page" due to how we do the circular tty buffers). NOTE! This case only handles the simpler non-icanon case, which is the one where people may care about throughput. I'm going to do the icanon case later too, because while performance isn't a major issue for that, there may be programs that think they'll always get a full line and don't like the 64-byte chunking for that reason. Such programs are arguably buggy (signals etc can cause random partial results from tty reads anyway), and good programs will handle such partial reads, but expecting everybody to write "good programs" has never been a winning policy for the kernel.. Signed-off-by: Linus Torvalds

tty: clean up legacy leftovers from n_tty line discipline

2021-01-21T00:48:48Z

Back when the line disciplines did their own direct user accesses, they had to deal with the data copy possibly failing in the middle. Now that the user copy is done by the tty_io.c code, that failure case no longer exists. Remove the left-over error handling code that cannot trigger. Signed-off-by: Linus Torvalds

tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer

2021-01-21T00:48:47Z

The tty line discipline .read() function was passed the final user pointer destination as an argument, which doesn't match the 'write()' function, and makes it very inconvenient to do a splice method for ttys. This is a conversion to use a kernel buffer instead. NOTE! It does this by passing the tty line discipline ->read() function an additional "cookie" to fill in, and an offset into the cookie data. The line discipline can fill in the cookie data with its own private information, and then the reader will repeat the read until either the cookie is cleared or it runs out of data. The only real user of this is N_HDLC, which can use this to handle big packets, even if the kernel buffer is smaller than the whole packet. Cc: Christoph Hellwig Cc: Greg Kroah-Hartman Cc: Al Viro Signed-off-by: Linus Torvalds