| Message ID | 20210505091928.22010-35-jslaby@suse.cz |
|---|---|
| State | Superseded |
| Headers | show |
| Series | None | expand |
On Wed, 2021-05-05 at 11:19 +0200, Jiri Slaby wrote: > Many tty drivers contain code to compute bits count depending on termios > cflags. So extract this code from serial core to a separate tty helper > function called tty_get_byte_size. [] > diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c [] > +/** > + * tty_get_byte_size - get size of a byte > + * @cflag: termios cflag value > + * @account_flags: account for start and stop bits, second stop bit (if > + * set), and parity (if set) > + * > + * Get the size of a byte in bits depending on @cflag. Depending on > + * @account_flags parameter, the result also accounts start and stop bits, > + * the second stop bit, and parity bit. > + */ > +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) > +{ > + unsigned char bits = account_flags ? 2 : 0; > + > + /* byte size and parity */ > + switch (cflag & CSIZE) { > + case CS5: > + bits += 5; > + break; > + case CS6: > + bits += 6; > + break; > + case CS7: > + bits += 7; > + break; > + case CS8: > + default: > + bits += 8; > + break; > + } > + > + if (account_flags && (cflag & CSTOPB)) > + bits++; > + > + if (account_flags && (cflag & PARENB)) > + bits++; > + > + return bits; > +} > +EXPORT_SYMBOL_GPL(tty_get_byte_size); Perhaps clearer not testing account_flags multiple times. unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) { unsigned char bits; /* byte size and parity */ switch (cflag & CSIZE) { case CS5: bits = 5; break; case CS6: bits = 6; break; case CS7: bits = 7; break; case CS8: default: bits = 8; break; } if (account_flags) { bits += 2; /* start/stop bits */ if (cflag & CSTOPB) bits++; if (cflag & PARENB) bits++; } return bits; }
On 06. 05. 21, 9:16, Joe Perches wrote: > On Wed, 2021-05-05 at 11:19 +0200, Jiri Slaby wrote: >> Many tty drivers contain code to compute bits count depending on termios >> cflags. So extract this code from serial core to a separate tty helper >> function called tty_get_byte_size. > [] >> diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c > [] >> +/** >> + * tty_get_byte_size - get size of a byte >> + * @cflag: termios cflag value >> + * @account_flags: account for start and stop bits, second stop bit (if >> + * set), and parity (if set) >> + * >> + * Get the size of a byte in bits depending on @cflag. Depending on >> + * @account_flags parameter, the result also accounts start and stop bits, >> + * the second stop bit, and parity bit. >> + */ >> +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) >> +{ >> + unsigned char bits = account_flags ? 2 : 0; >> + >> + /* byte size and parity */ >> + switch (cflag & CSIZE) { >> + case CS5: >> + bits += 5; >> + break; >> + case CS6: >> + bits += 6; >> + break; >> + case CS7: >> + bits += 7; >> + break; >> + case CS8: >> + default: >> + bits += 8; >> + break; >> + } >> + >> + if (account_flags && (cflag & CSTOPB)) >> + bits++; >> + >> + if (account_flags && (cflag & PARENB)) >> + bits++; >> + >> + return bits; >> +} >> +EXPORT_SYMBOL_GPL(tty_get_byte_size); > > Perhaps clearer not testing account_flags multiple times. Right. Originally, I had account_start_stop, account_stop, and account_parity parameters. But they were either all false or all true. So I unified them to account_flags, but the code remained overly complex. > unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) > { > unsigned char bits; > > /* byte size and parity */ > switch (cflag & CSIZE) { > case CS5: > bits = 5; > break; > case CS6: > bits = 6; > break; > case CS7: > bits = 7; > break; > case CS8: > default: > bits = 8; > break; > } > > if (account_flags) { > bits += 2; /* start/stop bits */ > > if (cflag & CSTOPB) > bits++; > > if (cflag & PARENB) > bits++; > } > > return bits; > } > > thanks, -- js suse labs
On 06. 05. 21, 10:24, Andy Shevchenko wrote: > if (!account_flags) > return bits; > > ? So I have: unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) { unsigned char bits; switch (cflag & CSIZE) { case CS5: bits = 5; break; case CS6: bits = 6; break; case CS7: bits = 7; break; case CS8: default: bits = 8; break; } if (!account_flags) return bits; if (cflag & CSTOPB) bits++; if (cflag & PARENB) bits++; return bits + 2; } thanks, -- js suse labs
On Thu, 2021-05-06 at 11:24 +0300, Andy Shevchenko wrote: > On Thursday, May 6, 2021, Joe Perches <joe@perches.com> wrote: [] > > Perhaps clearer not testing account_flags multiple times. > > > > unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) > > { > > unsigned char bits; > > > > /* byte size and parity */ nit: byte size, the parity bit is tested later. > > switch (cflag & CSIZE) { > > case CS5: > > bits = 5; > > break; > > case CS6: > > bits = 6; > > break; > > case CS7: > > bits = 7; > > break; > > case CS8: > > default: > > bits = 8; > > break; > > } > > > > if (account_flags) { > > > > if (!account_flags) > return bits; > > ? <shrug> six vs half dozen: 2 level indentation vs early return. I don't think 2 level indentation is too many. > > bits += 2; /* start/stop bits */ > > > > if (cflag & CSTOPB) > > bits++; > > > > if (cflag & PARENB) > > bits++; > > } Maybe comment each test as CSTOPB and PARENB aren't completely obvious.
On Thu, May 6, 2021 at 11:31 AM Jiri Slaby <jirislaby@kernel.org> wrote: > > On 06. 05. 21, 10:24, Andy Shevchenko wrote: > > if (!account_flags) > > return bits; > > > > ? > > So I have: Good to me, feel free to add Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> to this variant. > unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) > { > unsigned char bits; > > switch (cflag & CSIZE) { > case CS5: > bits = 5; > break; > case CS6: > bits = 6; > break; > case CS7: > bits = 7; > break; > case CS8: > default: > bits = 8; > break; > } > > if (!account_flags) > return bits; > > if (cflag & CSTOPB) > bits++; > if (cflag & PARENB) > bits++; > > return bits + 2; > } > > thanks, > -- > js > suse labs -- With Best Regards, Andy Shevchenko
On Mon, May 10, 2021 at 09:00:54AM +0200, Jiri Slaby wrote: > Many tty drivers contain code to compute bits count depending on termios > cflags. So extract this code from serial core to a separate tty helper > function called tty_get_byte_size. > > In the next patch, call to this new function will replace many copies of > this code. > > [v2] simplified the code flow as suggested by Joe and Andy > > Signed-off-by: Jiri Slaby <jslaby@suse.cz> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Cc: Joe Perches <joe@perches.com> > --- > drivers/tty/serial/serial_core.c | 30 +++-------------------- > drivers/tty/tty_ioctl.c | 42 ++++++++++++++++++++++++++++++++ > include/linux/tty.h | 2 ++ > 3 files changed, 47 insertions(+), 27 deletions(-) > > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > index d29329eb52f4..b3fc2b02a705 100644 > --- a/drivers/tty/serial/serial_core.c > +++ b/drivers/tty/serial/serial_core.c > @@ -334,39 +334,15 @@ void > uart_update_timeout(struct uart_port *port, unsigned int cflag, > unsigned int baud) > { > - unsigned int bits; > + unsigned int size; > > - /* byte size and parity */ > - switch (cflag & CSIZE) { > - case CS5: > - bits = 7; > - break; > - case CS6: > - bits = 8; > - break; > - case CS7: > - bits = 9; > - break; > - default: > - bits = 10; > - break; /* CS8 */ > - } > - > - if (cflag & CSTOPB) > - bits++; > - if (cflag & PARENB) > - bits++; > - > - /* > - * The total number of bits to be transmitted in the fifo. > - */ > - bits = bits * port->fifosize; > + size = tty_get_byte_size(cflag, true) * port->fifosize; > > /* > * Figure the timeout to send the above number of bits. > * Add .02 seconds of slop > */ > - port->timeout = (HZ * bits) / baud + HZ/50; > + port->timeout = (HZ * size) / baud + HZ/50; > } > > EXPORT_SYMBOL(uart_update_timeout); > diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c > index aa9ecc8be990..13acc3decd87 100644 > --- a/drivers/tty/tty_ioctl.c > +++ b/drivers/tty/tty_ioctl.c > @@ -300,6 +300,48 @@ int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b) > } > EXPORT_SYMBOL(tty_termios_hw_change); > > +/** > + * tty_get_byte_size - get size of a byte > + * @cflag: termios cflag value > + * @account_flags: account for start and stop bits, second stop bit (if > + * set), and parity (if set) > + * > + * Get the size of a byte in bits depending on @cflag. Depending on > + * @account_flags parameter, the result also accounts start and stop bits, > + * the second stop bit, and parity bit. > + */ > +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) > +{ > + unsigned char bits; > + > + switch (cflag & CSIZE) { > + case CS5: > + bits = 5; > + break; > + case CS6: > + bits = 6; > + break; > + case CS7: > + bits = 7; > + break; > + case CS8: > + default: > + bits = 8; > + break; > + } > + > + if (!account_flags) > + return bits; > + > + if (cflag & CSTOPB) > + bits++; > + if (cflag & PARENB) > + bits++; > + > + return bits + 2; > +} > +EXPORT_SYMBOL_GPL(tty_get_byte_size); This should really be two functions rather than passing a bool argument. I think naming them tty_get_word_size() and tty_get_frame_size() would be much more clear than than "byte size" + flag. I realise that the serial-driver interface only uses a cflag argument, but I think we should consider passing a pointer to the termios structure instead. Johan
On 10. 05. 21, 11:47, Johan Hovold wrote: >> --- a/drivers/tty/tty_ioctl.c >> +++ b/drivers/tty/tty_ioctl.c >> @@ -300,6 +300,48 @@ int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b) ... >> +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) >> +{ >> + unsigned char bits; >> + >> + switch (cflag & CSIZE) { >> + case CS5: >> + bits = 5; >> + break; >> + case CS6: >> + bits = 6; >> + break; >> + case CS7: >> + bits = 7; >> + break; >> + case CS8: >> + default: >> + bits = 8; >> + break; >> + } >> + >> + if (!account_flags) >> + return bits; >> + >> + if (cflag & CSTOPB) >> + bits++; >> + if (cflag & PARENB) >> + bits++; >> + >> + return bits + 2; >> +} >> +EXPORT_SYMBOL_GPL(tty_get_byte_size); > > This should really be two functions rather than passing a bool argument. > > I think naming them > > tty_get_word_size() > > and > > tty_get_frame_size() > > would be much more clear than than "byte size" + flag. Maybe I am screwed, but word means exactly 2B here. So instead, I would go for: s/word/char/ -- might be confused with C's char, 1B, or maybe not -- or s/word/data/ -- more generic and generally used in serial terminology. > I realise that the serial-driver interface only uses a cflag argument, > but I think we should consider passing a pointer to the termios > structure instead. That's impossible as termios is not always at hand. Examples are: pch_uart_startup -> uart_update_timeout sunsab_console_setup -> sunsab_convert_to_sab -> uart_update_timeout sunsu_kbd_ms_init -> sunsu_change_speed -> uart_update_timeout Let me document that in the commit. thanks, -- js suse labs
On Thu, May 13, 2021 at 09:24:03AM +0200, Jiri Slaby wrote: > On 10. 05. 21, 11:47, Johan Hovold wrote: > >> --- a/drivers/tty/tty_ioctl.c > >> +++ b/drivers/tty/tty_ioctl.c > >> @@ -300,6 +300,48 @@ int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b) > ... > >> +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) > >> +{ > >> + unsigned char bits; > >> + > >> + switch (cflag & CSIZE) { > >> + case CS5: > >> + bits = 5; > >> + break; > >> + case CS6: > >> + bits = 6; > >> + break; > >> + case CS7: > >> + bits = 7; > >> + break; > >> + case CS8: > >> + default: > >> + bits = 8; > >> + break; > >> + } > >> + > >> + if (!account_flags) > >> + return bits; > >> + > >> + if (cflag & CSTOPB) > >> + bits++; > >> + if (cflag & PARENB) > >> + bits++; > >> + > >> + return bits + 2; > >> +} > >> +EXPORT_SYMBOL_GPL(tty_get_byte_size); > > > > This should really be two functions rather than passing a bool argument. > > > > I think naming them > > > > tty_get_word_size() > > > > and > > > > tty_get_frame_size() > > > > would be much more clear than than "byte size" + flag. > > Maybe I am screwed, but word means exactly 2B here. No, not in this context. Some UART datasheets use "word" and "word length", while others use "character length" or "data bits" (and variations thereof). > So instead, I would > go for: > s/word/char/ -- might be confused with C's char, 1B, or maybe not -- or > s/word/data/ -- more generic and generally used in serial terminology. But "data size" it not very precise. I'd go for either tty_get_word_size() or tty_get_char_size(), and tty_get_frame_size() or possibly tty_get_data_bits(), and tty_get_frame_bits() Since posix and the termios interface use "CSIZE" (even if that "C" is ambiguous) and our man pages use "character size" perhaps we should stick with that and use: tty_get_char_size(), and tty_get_frame_size() That should be clear enough for everyone. > > I realise that the serial-driver interface only uses a cflag argument, > > but I think we should consider passing a pointer to the termios > > structure instead. > > That's impossible as termios is not always at hand. Examples are: > pch_uart_startup -> uart_update_timeout > sunsab_console_setup -> sunsab_convert_to_sab -> uart_update_timeout > sunsu_kbd_ms_init -> sunsu_change_speed -> uart_update_timeout > > Let me document that in the commit. Sounds good. Johan
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index d29329eb52f4..b3fc2b02a705 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -334,39 +334,15 @@ void uart_update_timeout(struct uart_port *port, unsigned int cflag, unsigned int baud) { - unsigned int bits; + unsigned int size; - /* byte size and parity */ - switch (cflag & CSIZE) { - case CS5: - bits = 7; - break; - case CS6: - bits = 8; - break; - case CS7: - bits = 9; - break; - default: - bits = 10; - break; /* CS8 */ - } - - if (cflag & CSTOPB) - bits++; - if (cflag & PARENB) - bits++; - - /* - * The total number of bits to be transmitted in the fifo. - */ - bits = bits * port->fifosize; + size = tty_get_byte_size(cflag, true) * port->fifosize; /* * Figure the timeout to send the above number of bits. * Add .02 seconds of slop */ - port->timeout = (HZ * bits) / baud + HZ/50; + port->timeout = (HZ * size) / baud + HZ/50; } EXPORT_SYMBOL(uart_update_timeout); diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c index aa9ecc8be990..72d036917b14 100644 --- a/drivers/tty/tty_ioctl.c +++ b/drivers/tty/tty_ioctl.c @@ -300,6 +300,47 @@ int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b) } EXPORT_SYMBOL(tty_termios_hw_change); +/** + * tty_get_byte_size - get size of a byte + * @cflag: termios cflag value + * @account_flags: account for start and stop bits, second stop bit (if + * set), and parity (if set) + * + * Get the size of a byte in bits depending on @cflag. Depending on + * @account_flags parameter, the result also accounts start and stop bits, + * the second stop bit, and parity bit. + */ +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags) +{ + unsigned char bits = account_flags ? 2 : 0; + + /* byte size and parity */ + switch (cflag & CSIZE) { + case CS5: + bits += 5; + break; + case CS6: + bits += 6; + break; + case CS7: + bits += 7; + break; + case CS8: + default: + bits += 8; + break; + } + + if (account_flags && (cflag & CSTOPB)) + bits++; + + if (account_flags && (cflag & PARENB)) + bits++; + + return bits; +} +EXPORT_SYMBOL_GPL(tty_get_byte_size); + /** * tty_set_termios - update termios values * @tty: tty to update diff --git a/include/linux/tty.h b/include/linux/tty.h index 5cf6b2e7331b..a14b4588368c 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -496,6 +496,8 @@ static inline speed_t tty_get_baud_rate(struct tty_struct *tty) return tty_termios_baud_rate(&tty->termios); } +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags); + extern void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old); extern int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b); extern int tty_set_termios(struct tty_struct *tty, struct ktermios *kt);
Many tty drivers contain code to compute bits count depending on termios cflags. So extract this code from serial core to a separate tty helper function called tty_get_byte_size. In the next patch, call to this new function will replace many copies of this code. Signed-off-by: Jiri Slaby <jslaby@suse.cz> --- drivers/tty/serial/serial_core.c | 30 +++-------------------- drivers/tty/tty_ioctl.c | 41 ++++++++++++++++++++++++++++++++ include/linux/tty.h | 2 ++ 3 files changed, 46 insertions(+), 27 deletions(-)