linux-kernel - Re: [PATCH v2 1/3] tty: Introduce UART_CAP

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Message-ID: <CAJs94EZ7ivHR0RQt2AfUy-6OmeeUNyQQ3izT5fzwmM5R8Kpf8Q@mail.gmail.com>
Date:	Sat, 7 Nov 2015 15:39:50 +0300
From:	"Matwey V. Kornilov" <matwey@....msu.ru>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>, jslaby@...e.com,
	linux-serial@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] tty: Introduce UART_CAP_HW485

2015-11-07 15:22 GMT+03:00 Peter Hurley <peter@...leysoftware.com>:
> On 11/07/2015 05:09 AM, Matwey V. Kornilov wrote:
>> Introduce new capability UART_CAP_HW485 to mark 8250 UARTs which have
>> hardware support of line direction control.
>
> Since capabilities are not exported to user-space, how will user-space
> know if the port only provides emulated 485 (eg., where only HW485 is
> acceptable)?

I cannot imagine the case when user really has to care about
implementation details.
In both cases the user will be provided with the consistent API
(TIOCGRS485/TIOCSRS485 ioctls) resulting into the same behavior.
Could you please expand your question?

>
> Regards,
> Peter Hurley
>
>> Signed-off-by: Matwey V. Kornilov <matwey@....msu.ru>
>> ---
>> Changes since v1:
>>  - Commit message has been wrapped
>>
>>  drivers/tty/serial/8250/8250.h         | 1 +
>>  drivers/tty/serial/8250/8250_fintek.c  | 1 +
>>  drivers/tty/serial/8250/8250_lpc18xx.c | 1 +
>>  drivers/tty/serial/8250/8250_pci.c     | 1 +
>>  4 files changed, 4 insertions(+)
>>
>> diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
>> index d54dcd8..92a4f47 100644
>> --- a/drivers/tty/serial/8250/8250.h
>> +++ b/drivers/tty/serial/8250/8250.h
>> @@ -69,6 +69,7 @@ struct serial8250_config {
>>       unsigned int    flags;
>>  };
>>
>> +#define UART_CAP_HW485       (1 << 7)        /* UART has hardware direction control for RS485 */
>>  #define UART_CAP_FIFO        (1 << 8)        /* UART has FIFO */
>>  #define UART_CAP_EFR (1 << 9)        /* UART has EFR */
>>  #define UART_CAP_SLEEP       (1 << 10)       /* UART has IER sleep */
>> diff --git a/drivers/tty/serial/8250/8250_fintek.c b/drivers/tty/serial/8250/8250_fintek.c
>> index 8947439..f2831a8 100644
>> --- a/drivers/tty/serial/8250/8250_fintek.c
>> +++ b/drivers/tty/serial/8250/8250_fintek.c
>> @@ -208,6 +208,7 @@ fintek_8250_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
>>       uart.port.iobase = pnp_port_start(dev, 0);
>>       uart.port.iotype = UPIO_PORT;
>>       uart.port.rs485_config = fintek_8250_rs485_config;
>> +     uart.capabilities = UART_CAP_HW485;
>>
>>       uart.port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
>>       if (pnp_irq_flags(dev, 0) & IORESOURCE_IRQ_SHAREABLE)
>> diff --git a/drivers/tty/serial/8250/8250_lpc18xx.c b/drivers/tty/serial/8250/8250_lpc18xx.c
>> index 99cd478..9d30276 100644
>> --- a/drivers/tty/serial/8250/8250_lpc18xx.c
>> +++ b/drivers/tty/serial/8250/8250_lpc18xx.c
>> @@ -175,6 +175,7 @@ static int lpc18xx_serial_probe(struct platform_device *pdev)
>>       uart.port.private_data = data;
>>       uart.port.rs485_config = lpc18xx_rs485_config;
>>       uart.port.serial_out = lpc18xx_uart_serial_out;
>> +     uart.capabilities = UART_CAP_HW485;
>>
>>       uart.dma = &data->dma;
>>       uart.dma->rxconf.src_maxburst = 1;
>> diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
>> index 4097f3f..c7c0ae9 100644
>> --- a/drivers/tty/serial/8250/8250_pci.c
>> +++ b/drivers/tty/serial/8250/8250_pci.c
>> @@ -1599,6 +1599,7 @@ static int pci_fintek_setup(struct serial_private *priv,
>>       port->port.iotype = UPIO_PORT;
>>       port->port.iobase = iobase;
>>       port->port.rs485_config = pci_fintek_rs485_config;
>> +     port->capabilities = UART_CAP_HW485;
>>
>>       data = devm_kzalloc(&pdev->dev, sizeof(u8), GFP_KERNEL);
>>       if (!data)
>>
>



-- 
With best regards,
Matwey V. Kornilov.
Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia
119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382
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