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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-01-19 00:31:30 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-01-21 03:48:47 +0300 |
| commit | 3b830a9c34d5897be07176ce4e6f2d75e2c8cfd7 (patch) | |
| tree | c0fbc7f3ff3d7525c548911e1132c4c130111af5 /include/linux/tty_ldisc.h | |
| parent | 9bb48c82aced07698a2d08ee0f1475a6c4f6b266 (diff) | |
| download | linux-3b830a9c34d5897be07176ce4e6f2d75e2c8cfd7.tar.xz | |
tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer
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 <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/tty_ldisc.h')
| -rw-r--r-- | include/linux/tty_ldisc.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h index b1e6043e9917..572a07976116 100644 --- a/include/linux/tty_ldisc.h +++ b/include/linux/tty_ldisc.h @@ -185,7 +185,8 @@ struct tty_ldisc_ops { void (*close)(struct tty_struct *); void (*flush_buffer)(struct tty_struct *tty); ssize_t (*read)(struct tty_struct *tty, struct file *file, - unsigned char __user *buf, size_t nr); + unsigned char *buf, size_t nr, + void **cookie, unsigned long offset); ssize_t (*write)(struct tty_struct *tty, struct file *file, const unsigned char *buf, size_t nr); int (*ioctl)(struct tty_struct *tty, struct file *file, |