Re: [PATCH] RS485: fix inconsistencies in the meaning of some variables
From: Claudio Scordino
Date: Tue Nov 08 2011 - 10:45:54 EST
Il 08/11/2011 16:02, Nicolas Ferre ha scritto:
> On 11/08/2011 11:48 AM, Claudio Scordino :
>> Il 08/11/2011 10:30, Nicolas Ferre ha scritto:
>>> On 11/04/2011 09:19 AM, Claudio Scordino :
>>>> Hi Alan, Hi Greg,
>>>>
>>>> it seems that the crisv10.c and the atmel_serial.c serial
>>>> drivers interpret the fields of the serial_rs485 structure in a
>>>> different
>>>> way.
>>>>
>>>> In particular, it seems that crisv10.c uses SER_RS485_RTS_AFTER_SEND and
>>>> SER_RS485_RTS_ON_SEND for the _logic value_ of the RTS pin;
>>>> atmel_serial.c, instead, uses these values to know if a _delay_ must be
>>>> set before and after sending.
>>>
>>> It seems sensible, but, on the other hand, I fear that this is a big
>>> change in the user interface: If people are already relying on this for
>>> their application, this can be difficult to understand the change. Can't
>>> we imagine an smoother migration path?
>>>
>>> It seems from de6f86ce5 that 16C950 may also use rs485 mode (with
>>> another signal that RTS BTW)...
>>>
>>> See comments online...
>>>
>>>> This patch makes the usage of these variables consistent across all
>>>> drivers and fixes the Documentation as well.
>>>> In particular, SER_RS485_RTS_AFTER_SEND and SER_RS485_RTS_ON_SEND will
>>>> be used to set the logic value of the RTS pin (as in the crisv10.c
>>>> driver); the delay is understood by looking only at the value of
>>>> delay_rts_before_send and delay_rts_after_send.
>>>>
>>>> Best regards,
>>>>
>>>> Claudio
>>>>
>>>>
>>>> Subject: RS485: fix inconsistencies in the meaning of some variables
>>>> From: Claudio Scordino<claudio@xxxxxxxxxxxxxxx>
>>>>
>>>> The crisv10.c and the atmel_serial.c serial drivers interpret the fields
>>>> of the serial_rs485 structure in a different way.
>>>> In particular, crisv10.c uses SER_RS485_RTS_AFTER_SEND and
>>>> SER_RS485_RTS_ON_SEND for the voltage of the RTS pin; atmel_serial.c,
>>>> instead,
>>>> uses these values to know if a delay must be set before and after
>>>> sending.
>>>> This patch makes the usage of these variables consistent across all
>>>> drivers and
>>>> fixes the Documentation as well.
>>>>> From now on, SER_RS485_RTS_AFTER_SEND and SER_RS485_RTS_ON_SEND
>>>> will be used to
>>>> set the voltage of the RTS pin (as in the crisv10.c driver); the
>>>> delay will be
>>>> understood by looking only at the value of delay_rts_before_send and
>>>> delay_rts_after_send.
>>>
>>> Ok, but don't you think that the flags names are not so much
>>> self-explanatory for this new meaning?
>>>
>>> What about:
>>> SER_RS485_RTS_LEVEL_DURING_SEND
>>> SER_RS485_RTS_VALUE_DURING_SEND (maybe too vague?)
>>> SER_RS485_RTS_LOGICAL_VALUE_DURING_SEND (maybe too long?)
>>>
>>> Moreover, can't we just use one property for this? I mean, if RTS
>>> logical value is high during the sending of data, can it mean that RTS
>>> will be low before and after? And the other way around: if the signal is
>>> low during data send, will it be high before and after?
>>>
>>> Here again, changing the user interface is not a good idea, so I fear
>>> that it can be a show stopper.
>>
>> Hi Nicolas,
>>
>> I understand, but honestly I do not agree.
>>
>> The current state is inconsistent, and leaving the status quo can only
>> bring to more issues in the future (because it is not clear if the
>> interface should be used either as in the Cris or in the Atmel driver).
>> That's why I think it should be fixed ASAP (before further drivers start
>> using it).
>>
>> The modifications that I have proposed are very minimal, and most
>> user-space code should continue to work without any difference. Any Cris
>> user-space code will continue to work, because we didn't change the
>> behavior of the driver. For Atmel user-space code, instead, the behavior
>> of the driver changes only if flags are not set and delay variables
>> contain a value different than 0 (which, hopefully, is not a very common
>> situation).
>
> Ok then. I was fearing that, with Atmel driver, someone can set
> SER_RS485_RTS_AFTER_SEND to tell that the delay is needed but not
> necessarily that the signal level is "high".
>
> But you are right telling that this inconstancy should be addressed.
>
>> That's the reason why I preferred to not change the names of
>> the variables, even if better names would be desirable.
>
> 100% agree with this.
>
>> If you want, I can re-format the patch according to you suggestions,
>
> Yes
>
>> remove formatted lines
>
> Yes
Hi all,
please find below a better formatted patch.
Best regards,
Claudio
Subject: RS485: fix inconsistencies in the meaning of some variables
From: Claudio Scordino <claudio@xxxxxxxxxxxxxxx>
The crisv10.c and the atmel_serial.c serial drivers intepret the fields of the
serial_rs485 structure in a different way.
In particular, crisv10.c uses SER_RS485_RTS_AFTER_SEND and
SER_RS485_RTS_ON_SEND for the voltage of the RTS pin; atmel_serial.c, instead,
uses these values to know if a delay must be set before and after sending.
This patch makes the usage of these variables consistent across all drivers and
fixes the Documentation as well.
>From now on, SER_RS485_RTS_AFTER_SEND and SER_RS485_RTS_ON_SEND will be used to
set the voltage of the RTS pin (as in the crisv10.c driver); the delay will be
understood by looking only at the value of delay_rts_before_send and
delay_rts_after_send.
Signed-off-by: Claudio Scordino <claudio@xxxxxxxxxxxxxxx>
Signed-off-by: Darron Black <darron@xxxxxxxxxxx>
---
Documentation/serial/serial-rs485.txt | 14 +++++++++++---
drivers/tty/serial/atmel_serial.c | 16 +++-------------
drivers/tty/serial/crisv10.c | 10 ++--------
include/linux/serial.h | 14 ++++++++------
4 files changed, 24 insertions(+), 30 deletions(-)
diff --git a/Documentation/serial/serial-rs485.txt b/Documentation/serial/serial-rs485.txt
index 079cb3d..41c8378 100644
--- a/Documentation/serial/serial-rs485.txt
+++ b/Documentation/serial/serial-rs485.txt
@@ -97,15 +97,23 @@
struct serial_rs485 rs485conf;
- /* Set RS485 mode: */
+ /* Enable RS485 mode: */
rs485conf.flags |= SER_RS485_ENABLED;
+ /* Set logical level for RTS pin equal to 1 when sending: */
+ rs485conf.flags |= SER_RS485_RTS_ON_SEND;
+ /* or, set logical level for RTS pin equal to 0 when sending: */
+ rs485conf.flags &= ~(SER_RS485_RTS_ON_SEND);
+
+ /* Set logical level for RTS pin equal to 1 after sending: */
+ rs485conf.flags |= SER_RS485_RTS_AFTER_SEND;
+ /* or, set logical level for RTS pin equal to 0 after sending: */
+ rs485conf.flags &= ~(SER_RS485_RTS_AFTER_SEND);
+
/* Set rts delay before send, if needed: */
- rs485conf.flags |= SER_RS485_RTS_BEFORE_SEND;
rs485conf.delay_rts_before_send = ...;
/* Set rts delay after send, if needed: */
- rs485conf.flags |= SER_RS485_RTS_AFTER_SEND;
rs485conf.delay_rts_after_send = ...;
/* Set this flag if you want to receive data even whilst sending data */
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 4a0f86f..4c823f3 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -228,7 +228,7 @@ void atmel_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf)
if (rs485conf->flags & SER_RS485_ENABLED) {
dev_dbg(port->dev, "Setting UART to RS485\n");
atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
- if (rs485conf->flags & SER_RS485_RTS_AFTER_SEND)
+ if ((rs485conf->delay_rts_after_send) > 0)
UART_PUT_TTGR(port, rs485conf->delay_rts_after_send);
mode |= ATMEL_US_USMODE_RS485;
} else {
@@ -304,7 +304,7 @@ static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
dev_dbg(port->dev, "Setting UART to RS485\n");
- if (atmel_port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
+ if ((atmel_port->rs485.delay_rts_after_send) > 0)
UART_PUT_TTGR(port,
atmel_port->rs485.delay_rts_after_send);
mode |= ATMEL_US_USMODE_RS485;
@@ -1228,7 +1228,7 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
dev_dbg(port->dev, "Setting UART to RS485\n");
- if (atmel_port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
+ if ((atmel_port->rs485.delay_rts_after_send) > 0)
UART_PUT_TTGR(port,
atmel_port->rs485.delay_rts_after_send);
mode |= ATMEL_US_USMODE_RS485;
@@ -1447,16 +1447,6 @@ static void __devinit atmel_of_init_port(struct atmel_uart_port *atmel_port,
rs485conf->delay_rts_after_send = rs485_delay[1];
rs485conf->flags = 0;
- if (rs485conf->delay_rts_before_send == 0 &&
- rs485conf->delay_rts_after_send == 0) {
- rs485conf->flags |= SER_RS485_RTS_ON_SEND;
- } else {
- if (rs485conf->delay_rts_before_send)
- rs485conf->flags |= SER_RS485_RTS_BEFORE_SEND;
- if (rs485conf->delay_rts_after_send)
- rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
- }
-
if (of_get_property(np, "rs485-rx-during-tx", NULL))
rs485conf->flags |= SER_RS485_RX_DURING_TX;
diff --git a/drivers/tty/serial/crisv10.c b/drivers/tty/serial/crisv10.c
index b743504..1dfba7b 100644
--- a/drivers/tty/serial/crisv10.c
+++ b/drivers/tty/serial/crisv10.c
@@ -3234,9 +3234,8 @@ rs_write(struct tty_struct *tty,
e100_disable_rx(info);
e100_enable_rx_irq(info);
#endif
- if ((info->rs485.flags & SER_RS485_RTS_BEFORE_SEND) &&
- (info->rs485.delay_rts_before_send > 0))
- msleep(info->rs485.delay_rts_before_send);
+ if (info->rs485.delay_rts_before_send > 0)
+ msleep(info->rs485.delay_rts_before_send);
}
#endif /* CONFIG_ETRAX_RS485 */
@@ -3693,10 +3692,6 @@ rs_ioctl(struct tty_struct *tty,
rs485data.delay_rts_before_send = rs485ctrl.delay_rts_before_send;
rs485data.flags = 0;
- if (rs485data.delay_rts_before_send != 0)
- rs485data.flags |= SER_RS485_RTS_BEFORE_SEND;
- else
- rs485data.flags &= ~(SER_RS485_RTS_BEFORE_SEND);
if (rs485ctrl.enabled)
rs485data.flags |= SER_RS485_ENABLED;
@@ -4531,7 +4526,6 @@ static int __init rs_init(void)
/* Set sane defaults */
info->rs485.flags &= ~(SER_RS485_RTS_ON_SEND);
info->rs485.flags |= SER_RS485_RTS_AFTER_SEND;
- info->rs485.flags &= ~(SER_RS485_RTS_BEFORE_SEND);
info->rs485.delay_rts_before_send = 0;
info->rs485.flags &= ~(SER_RS485_ENABLED);
#endif
diff --git a/include/linux/serial.h b/include/linux/serial.h
index 97ff8e2..3d86517 100644
--- a/include/linux/serial.h
+++ b/include/linux/serial.h
@@ -207,13 +207,15 @@ struct serial_icounter_struct {
struct serial_rs485 {
__u32 flags; /* RS485 feature flags */
-#define SER_RS485_ENABLED (1 << 0)
-#define SER_RS485_RTS_ON_SEND (1 << 1)
-#define SER_RS485_RTS_AFTER_SEND (1 << 2)
-#define SER_RS485_RTS_BEFORE_SEND (1 << 3)
+#define SER_RS485_ENABLED (1 << 0) /* If enabled */
+#define SER_RS485_RTS_ON_SEND (1 << 1) /* Logical level for
+ RTS pin when
+ sending */
+#define SER_RS485_RTS_AFTER_SEND (1 << 2) /* Logical level for
+ RTS pin after sent*/
#define SER_RS485_RX_DURING_TX (1 << 4)
- __u32 delay_rts_before_send; /* Milliseconds */
- __u32 delay_rts_after_send; /* Milliseconds */
+ __u32 delay_rts_before_send; /* Delay before send (milliseconds) */
+ __u32 delay_rts_after_send; /* Delay after send (milliseconds) */
__u32 padding[5]; /* Memory is cheap, new structs
are a royal PITA .. */
};
--
1.7.1
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