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From: Jiri Slaby <jirislaby@kernel.org>
To: Joe Perches <joe@perches.com>, gregkh@linuxfoundation.org
Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 34/35] tty: make tty_get_byte_size available
Date: Thu, 6 May 2021 09:19:32 +0200	[thread overview]
Message-ID: <949f77aa-2429-3fe9-9163-5a7b2c5c499a@kernel.org> (raw)
In-Reply-To: <ef1bd57095e941560530be43806791966a6735ad.camel@perches.com>

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

  reply	other threads:[~2021-05-06  7:19 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-05  9:18 [PATCH 00/35] tty cleanup for 5.14 Jiri Slaby
2021-05-05  9:18 ` [PATCH 01/35] tty: remove broken r3964 line discipline Jiri Slaby
2021-05-05  9:26   ` Greg KH
2021-05-05  9:18 ` [PATCH 02/35] n_tty: remove n_tty_receive_char wrapper Jiri Slaby
2021-05-05  9:18 ` [PATCH 03/35] n_tty: remove n_tty_receive_char_fast Jiri Slaby
2021-05-05  9:18 ` [PATCH 04/35] n_tty: drop n_tty_receive_buf_fast Jiri Slaby
2021-05-05  9:18 ` [PATCH 05/35] n_tty: drop parmrk_dbl from n_tty_receive_char Jiri Slaby
2021-05-05  9:18 ` [PATCH 06/35] n_tty: move lnext handling Jiri Slaby
2021-05-05  9:19 ` [PATCH 07/35] n_tty: make n_tty_receive_char_special return void Jiri Slaby
2021-05-05  9:19 ` [PATCH 08/35] n_tty: do only one cp dereference in n_tty_receive_buf_standard Jiri Slaby
2021-05-05  9:19 ` [PATCH 09/35] n_tty: invert TTY_NORMAL condition " Jiri Slaby
2021-05-05  9:19 ` [PATCH 10/35] n_tty: remove superfluous return from n_tty_receive_signal_char Jiri Slaby
2021-05-05  9:19 ` [PATCH 11/35] tty: make fp of tty_ldisc_ops::receive_buf{,2} const Jiri Slaby
2021-05-05  9:19 ` [PATCH 12/35] tty: cumulate and document tty_struct::flow* members Jiri Slaby
2021-05-05  9:19 ` [PATCH 13/35] tty: cumulate and document tty_struct::ctrl* members Jiri Slaby
2021-05-05  9:19 ` [PATCH 14/35] tty: set tty_ldisc_ops::num statically Jiri Slaby
2021-05-05  9:19 ` [PATCH 15/35] n_gsm: use goto-failpaths in gsm_init Jiri Slaby
2021-05-05  9:19 ` [PATCH 16/35] tty: make tty_ldisc_ops a param in tty_unregister_ldisc Jiri Slaby
2021-05-05  9:19 ` [PATCH 17/35] tty: drop tty_ldisc_ops::refcount Jiri Slaby
2021-05-05  9:19 ` [PATCH 18/35] tty: no checking of tty_unregister_ldisc Jiri Slaby
2021-05-05  9:19 ` [PATCH 19/35] tty: return void from tty_unregister_ldisc Jiri Slaby
2021-05-05  9:19 ` [PATCH 20/35] ti-st: use goto-failpath in st_core_init Jiri Slaby
2021-05-05  9:19 ` [PATCH 21/35] ti-st: use tty_write_room Jiri Slaby
2021-05-05  9:19 ` [PATCH 22/35] tty: make tty_operations::write_room return uint Jiri Slaby
2021-05-05  9:25   ` Geert Uytterhoeven
2021-05-05 10:34   ` Anton Ivanov
2021-05-05 10:43   ` David Sterba
2021-05-05 11:53   ` Max Filippov
2021-05-05 12:15   ` Alex Elder
2021-05-10 11:27   ` Laurentiu Tudor
2021-05-05  9:19 ` [PATCH 23/35] USB: serial: make usb_serial_driver::write_room " Jiri Slaby
2021-05-19  9:07   ` Johan Hovold
2021-05-05  9:19 ` [PATCH 24/35] tty: make tty_buffer_space_avail " Jiri Slaby
2021-05-05  9:19 ` [PATCH 25/35] tty: remove tty_operations::chars_in_buffer for non-buffering Jiri Slaby
2021-05-05 11:51   ` Max Filippov
2021-05-06  5:47   ` Jiri Slaby
2021-05-06  5:56     ` Greg KH
2021-05-05  9:19 ` [PATCH 26/35] tty: make tty_operations::chars_in_buffer return uint Jiri Slaby
2021-05-05 10:34   ` Anton Ivanov
2021-05-05 10:43   ` David Sterba
2021-05-05  9:19 ` [PATCH 27/35] serial: make usb_serial_driver::chars_in_buffer " Jiri Slaby
2021-05-19  9:09   ` Johan Hovold
2021-05-05  9:19 ` [PATCH 28/35] nozomi: simplify ntty_chars_in_buffer Jiri Slaby
2021-05-05  9:19 ` [PATCH 29/35] USB: serial: digi_acceleport, simplify digi_chars_in_buffer Jiri Slaby
2021-05-19  9:11   ` Johan Hovold
2021-05-05  9:19 ` [PATCH 30/35] tty: remove empty tty_operations::flush_buffer Jiri Slaby
2021-05-05  9:19 ` [PATCH 31/35] tty: remove empty tty_operations::set_termios Jiri Slaby
2021-05-05 10:34   ` Anton Ivanov
2021-05-05  9:19 ` [PATCH 32/35] isdn: capi, remove optional tty ops Jiri Slaby
2021-05-05  9:19 ` [PATCH 33/35] isdn: capi, drop useless pr_debugs Jiri Slaby
2021-05-05  9:19 ` [PATCH 34/35] tty: make tty_get_byte_size available Jiri Slaby
2021-05-06  7:16   ` Joe Perches
2021-05-06  7:19     ` Jiri Slaby [this message]
     [not found]     ` <CAHp75Vfq6ABW7ukwaKmZOF2DszmuHD28S=wcLcFowvRdXTnWmg@mail.gmail.com>
2021-05-06  8:31       ` Jiri Slaby
2021-05-06  9:33         ` Andy Shevchenko
2021-05-06  8:35       ` Joe Perches
2021-05-10  7:00   ` [PATCH v2 " Jiri Slaby
2021-05-10  9:47     ` Johan Hovold
2021-05-13  7:24       ` Jiri Slaby
2021-05-13  9:41         ` Johan Hovold
2021-05-05  9:19 ` [PATCH 35/35] tty: make use of tty_get_byte_size Jiri Slaby
2021-05-10  9:59   ` Johan Hovold
2021-05-13 15:04 ` [PATCH 00/35] tty cleanup for 5.14 Greg KH
2021-05-13 16:20   ` Johan Hovold
2021-05-13 16:29     ` Greg KH
2021-05-14  8:11       ` Johan Hovold
2021-06-10  9:02 ` [PATCH v3 1/4] tty: make tty_get_{char,frame}_size available Jiri Slaby
2021-06-10  9:02   ` [PATCH v3 2/4] mxs-auart: redefine AUART_LINECTRL_WLEN to accept bits count Jiri Slaby
2021-06-10  9:02   ` [PATCH v3 3/4] cypress_m8: switch data_bits to real character bits Jiri Slaby
2021-06-10  9:02   ` [PATCH v3 4/4] tty: make use of tty_get_{char,frame}_size Jiri Slaby
2021-06-10 15:15     ` Alex Elder

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