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

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Date:	Sat, 7 Nov 2015 10:32:39 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	"Matwey V. Kornilov" <matwey@....msu.ru>
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

On 11/07/2015 07:39 AM, Matwey V. Kornilov wrote:
> 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?

Well, the entire serial core is a 'consistent' API but yet we
still report to user-space what the port type is. Same with lspci
and lsusb.

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)
>>>
>>
> 
> 
> 

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