kernel/linux.git/drivers/tty/n_tty.c, branch v5.15.7

tty: drop tty_ldisc_ops::refcount

2021-05-13T14:57:17+00:00

The refcount is checked only in tty_unregister_ldisc and EBUSY returned if it is nonzero. But none of the tty_unregister_ldisc callers act anyhow if this (or any other) error is returned. So remove tty_ldisc_ops::refcount completely and make tty_unregister_ldisc return 'void' in the next patches. That means we assume tty_unregister_ldisc is not called while the ldisc might be in use. That relies on try_module_get in get_ldops and module_put in put_ldops. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210505091928.22010-18-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

tty: set tty_ldisc_ops::num statically

2021-05-13T14:57:16+00:00

There is no reason to pass the ldisc number to tty_register_ldisc separately. Just set it in the already defined tty_ldisc_ops in all the ldiscs. This simplifies tty_register_ldisc a bit too (no need to set the num member there). Signed-off-by: Jiri Slaby Cc: William Hubbs Cc: Chris Brannon Cc: Kirk Reiser Cc: Samuel Thibault Cc: Marcel Holtmann Cc: Johan Hedberg Cc: Luiz Augusto von Dentz Cc: Dmitry Torokhov Cc: Arnd Bergmann Cc: "David S. Miller" Cc: Jakub Kicinski Cc: Wolfgang Grandegger Cc: Marc Kleine-Budde Cc: Andreas Koensgen Cc: Paul Mackerras Cc: Rodolfo Giometti Cc: Peter Ujfalusi Cc: Liam Girdwood Cc: Mark Brown Cc: Jaroslav Kysela Cc: Takashi Iwai Link: https://lore.kernel.org/r/20210505091928.22010-15-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

tty: cumulate and document tty_struct::ctrl* members

2021-05-13T14:57:16+00:00

Group the ctrl members under a single struct called ctrl. The new struct contains 'pgrp', 'session', 'pktstatus', and 'packet'. 'pktstatus' and 'packet' used to be bits in a bitfield. The struct also contains the lock protecting them to share the same cache line. Note that commit c545b66c6922b (tty: Serialize tcflow() with other tty flow control changes) added a padding to the original bitfield. It was for the bitfield to occupy a whole 64b word to avoid interferring stores on Alpha (cannot we evaporate this arch with weird implications to C code yet?). But it doesn't work as expected as the padding (tty_struct::ctrl_unused) is aligned to a 8B boundary too and occupies some bytes from the next word. So make it reliable by: 1) setting __aligned of the struct -- that aligns the start, and 2) making 'unsigned long unused[0]' as the last member of the struct -- pads the end. Add a kerneldoc comment for this grouped members. Signed-off-by: Jiri Slaby Cc: "David S. Miller" Cc: Jakub Kicinski Cc: netdev@vger.kernel.org Link: https://lore.kernel.org/r/20210505091928.22010-14-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

tty: cumulate and document tty_struct::flow* members

2021-05-13T14:57:16+00:00

Group the flow flags under a single struct called flow. The new struct contains 'stopped' and 'tco_stopped' bools which used to be bits in a bitfield. The struct also contains the lock protecting them to potentially share the same cache line. Note that commit c545b66c6922b (tty: Serialize tcflow() with other tty flow control changes) added a padding to the original bitfield. It was for the bitfield to occupy a whole 64b word to avoid interferring stores on Alpha (cannot we evaporate this arch with weird implications to C code yet?). But it doesn't work as expected as the padding (tty_struct::unused) is aligned to a 8B boundary too and occupies some bytes from the next word. So make it reliable by: 1) setting __aligned of the struct -- that aligns the start, and 2) making 'unsigned long unused[0]' as the last member of the struct -- pads the end. This is also the perfect time to start the documentation of tty_struct where all this lives. So we start by documenting what these bools actually serve for. And why we do all the alignment dances. Only the few up-to-date information from the Theodore's comment made it into this new Kerneldoc comment. Signed-off-by: Jiri Slaby Cc: "David S. Miller" Cc: Jakub Kicinski Cc: Jonathan Corbet Cc: Arnd Bergmann Cc: Ulf Hansson Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Shawn Guo Cc: Sascha Hauer Cc: Vineet Gupta Cc: "Maciej W. Rozycki" Link: https://lore.kernel.org/r/20210505091928.22010-13-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

tty: make fp of tty_ldisc_ops::receive_buf{,2} const

2021-05-13T14:57:16+00:00

Char pointer (cp) passed to tty_ldisc_ops::receive_buf{,2} is const. There is no reason for flag pointer (fp) not to be too. So switch it in the definition and all uses. Signed-off-by: Jiri Slaby Cc: William Hubbs Cc: Chris Brannon Cc: Kirk Reiser Cc: Samuel Thibault Cc: Marcel Holtmann Cc: Johan Hedberg Cc: Luiz Augusto von Dentz Cc: Dmitry Torokhov Cc: Arnd Bergmann Cc: "David S. Miller" Cc: Jakub Kicinski Cc: Wolfgang Grandegger Cc: Marc Kleine-Budde Cc: Andreas Koensgen Cc: Paul Mackerras Cc: Liam Girdwood Cc: Mark Brown Cc: Jaroslav Kysela Cc: Takashi Iwai Cc: Peter Ujfalusi Link: https://lore.kernel.org/r/20210505091928.22010-12-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

n_tty: remove superfluous return from n_tty_receive_signal_char

2021-05-13T14:57:16+00:00

A return at the end of a void-returning function is superfluous. Get rid of it. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210505091928.22010-11-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

n_tty: invert TTY_NORMAL condition in n_tty_receive_buf_standard

2021-05-13T14:57:16+00:00

Handle !TTY_NORMAL as a short path and 'continue' the loop. Do the rest as a normal code flow. This decreases the indentation level by one and makes the code flow more understandable. IOW, we avoid if (cond) { LONG CODE; } else single_line(); by if (!cond) { single_line(); continue; } LONG CODE; While at it, invert also the 'if (!test_bit) A else B' into 'if (test_bit) B else A'. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210505091928.22010-10-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

n_tty: do only one cp dereference in n_tty_receive_buf_standard

2021-05-13T14:57:16+00:00

It might be confusing for readers: there are three distinct dereferences and increments of 'cp' in n_tty_receive_buf_standard. Do it on a single place, along with/before the 'fp' dereference. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210505091928.22010-9-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

n_tty: make n_tty_receive_char_special return void

2021-05-13T14:57:16+00:00

After the previous patch, noone cares about the return value of n_tty_receive_char_special. ldata->lnext is checked instead. So switch return type of n_tty_receive_char_special to void. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210505091928.22010-8-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

n_tty: move lnext handling

2021-05-13T14:57:16+00:00

Move lnext handling from __receive_buf to n_tty_receive_buf_standard. It simplifies the handling as it needs not fetching 'flag' and decrement 'count' in __receive_buf. Instead, all this is left up to the loop in n_tty_receive_buf_standard which already does that. This way, no need to repeat the action when n_tty_receive_char_special returns true -- ldata->lnext is set there in that case, so the 'if (ldata->lnext)' check is sufficient. The next patch will switch n_tty_receive_char_special to return 'void'. The result is much simplified code flow. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20210505091928.22010-7-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman