Re: [PATCH v2 1/3] tty: Introduce UART_CAP_HW485

Peter Hurley
2015-11-07T15:32:48Z

On 11/07/2015 07:39 AM, Matwey V. Kornilov wrote:
> 2015-11-07 15:22 GMT+03:00 Peter Hurley <peter@hurleysoftware.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@sai.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)
>>>
>>
>
>
>