Re: [PATCH 1/2] serial: 8250: Allow port registration without UPF_BOOT_AUTOCONF

Esben Haabendal
2019-04-26T17:10:16Z

Andy Shevchenko <andriy.shevchenko@linux.intel.com> writes:

> On Fri, Apr 26, 2019 at 10:40:37AM +0200, Esben Haabendal wrote:
>> With serial8250_register_8250_port() forcing UPF_BOOT_AUTOCONF bit on, it
>> is not possible to register a port without having
>> serial8250_request_std_resource() called.
>>
>> For adding a 8250 port to an MFD device, this is problematic, as the
>> request_mem_region() call will fail, as the MFD device (and rightly so)
>> has requested the region. For this case, the 8250 port should accept
>> having passed mapbase and membase, and just use that.
>
> You need to simple set port type and use UPF_FIXED_TYPE.
> No need for this patch.

The reason for this patch is to be able to do exactly that (set port
type and UPF_FIXED_TYPE) without having UPF_BOOT_AUTOCONF added.

In the current serial8250_register_8250_port() there is:

uart->port.flags = up->port.flags | UPF_BOOT_AUTOCONF;

So, even though I set UPF_FIXED_TYPE, I get
UPF_FIXED_TYPE|UPF_BOOT_AUTOCONF. So I need this patch.

I think it is unfortunate that UPF_BOOT_AUTOCONF is or'ed to flags like
that, but changing that will surely break stuff.

/Esben

>
>>
>> Signed-off-by: Esben Haabendal <esben@geanix.com>
>> ---
>> drivers/tty/serial/8250/8250_core.c | 36 +++++++++++++++++++++---------------
>> include/linux/serial_8250.h | 2 ++
>> 2 files changed, 23 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
>> index e441221..ddbb0a0 100644
>> --- a/drivers/tty/serial/8250/8250_core.c
>> +++ b/drivers/tty/serial/8250/8250_core.c
>> @@ -957,20 +957,8 @@ static void serial_8250_overrun_backoff_work(struct work_struct *work)
>> spin_unlock_irqrestore(&port->lock, flags);
>> }
>>
>> -/**
>> - * serial8250_register_8250_port - register a serial port
>> - * @up: serial port template
>> - *
>> - * Configure the serial port specified by the request. If the
>> - * port exists and is in use, it is hung up and unregistered
>> - * first.
>> - *
>> - * The port is then probed and if necessary the IRQ is autodetected
>> - * If this fails an error is returned.
>> - *
>> - * On success the port is ready to use and the line number is returned.
>> - */
>> -int serial8250_register_8250_port(struct uart_8250_port *up)
>> +int __serial8250_register_8250_port(struct uart_8250_port *up,
>> + unsigned int extra_flags)
>> {
>> struct uart_8250_port *uart;
>> int ret = -ENOSPC;
>> @@ -993,7 +981,7 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>> uart->port.fifosize = up->port.fifosize;
>> uart->port.regshift = up->port.regshift;
>> uart->port.iotype = up->port.iotype;
>> - uart->port.flags = up->port.flags | UPF_BOOT_AUTOCONF;
>> + uart->port.flags = up->port.flags | extra_flags;
>> uart->bugs = up->bugs;
>> uart->port.mapbase = up->port.mapbase;
>> uart->port.mapsize = up->port.mapsize;
>> @@ -1086,6 +1074,24 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>>
>> return ret;
>> }
>> +
>> +/**
>> + * serial8250_register_8250_port - register a serial port
>> + * @up: serial port template
>> + *
>> + * Configure the serial port specified by the request. If the
>> + * port exists and is in use, it is hung up and unregistered
>> + * first.
>> + *
>> + * The port is then probed and if necessary the IRQ is autodetected
>> + * If this fails an error is returned.
>> + *
>> + * On success the port is ready to use and the line number is returned.
>> + */
>> +int serial8250_register_8250_port(struct uart_8250_port *up)
>> +{
>> + return __serial8250_register_8250_port(up, UPF_BOOT_AUTOCONF);
>> +}
>> EXPORT_SYMBOL(serial8250_register_8250_port);
>>
>> /**
>> diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
>> index 5a655ba..9d1fe2e 100644
>> --- a/include/linux/serial_8250.h
>> +++ b/include/linux/serial_8250.h
>> @@ -145,6 +145,8 @@ static inline struct uart_8250_port *up_to_u8250p(struct uart_port *up)
>> return container_of(up, struct uart_8250_port, port);
>> }
>>
>> +extern int __serial8250_register_8250_port(struct uart_8250_port *,
>> + unsigned int);
>> int serial8250_register_8250_port(struct uart_8250_port *);
>> void serial8250_unregister_port(int line);
>> void serial8250_suspend_port(int line);
>> --
>> 2.4.11
>>