linux-kernel - Re: [PATCH] serial: 8250: 8250_core: Fix irq name for 8250 serial irq

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Message-ID: <CAHp75Vd7Q_0MZ69kojA_S_A4OOgdD5sR1MKW_NLXrZa6h+3GSA@mail.gmail.com>
Date:   Thu, 16 Mar 2017 22:58:54 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Vignesh R <vigneshr@...com>,
        Jisheng Zhang <jszhang@...vell.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Jiri Slaby <jslaby@...e.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] serial: 8250: 8250_core: Fix irq name for 8250 serial irq

On Thu, Mar 16, 2017 at 4:55 PM, Robin Murphy <robin.murphy@....com> wrote:
> On 16/03/17 13:36, Russell King - ARM Linux wrote:
>> On Thu, Mar 16, 2017 at 05:56:53PM +0530, Vignesh R wrote:
>>> Using dev_name() as irq name during request_irq() might be misleading in
>>> case of serial over PCI. Therefore use a better alternative name for
>>> identifying serial port irqs as "serial" appended with serial_index of
>>> the port. This ensures that "serial" string is always present in irq
>>> name while port index will help in distinguishing b/w different ports.
>>
>> Wouldn't it be better to use the device name (iow, ttySx) rather than
>> "serialx" ?
>>
>> Maybe a helper function in serial_core.c to format the device name into
>> a supplied string, which can be re-used elsewhere, eg, uart_report_port()
>> and uart_suspend_port().  IOW:
>>
>> const char *uart_port_name(char *buf, size_t n, struct uart_driver *drv,
>>                          struct uart_port *port)
>> {
>>       snprintf(buf, n, "%s%d", drv->dev_name,
>>                drv->tty_driver->name_base + port->line);
>>
>>       return buf;
>> }
>>
>> which means you can do this:
>>
>>       char name[16];
>>
>>       request_irq(..., uart_port_name(name, sizeof(name), driver, port), ...)
>>
>> which also avoids the allocation.
>
> ...and makes 'cat /proc/interrupts' particularly fun later:
>
>   8:          0          GICv2  72 Level     � �h       ����V!
>
> Unless a suitably long-lived string already exists somewhere else in the
> serial core, the allocation is unavoidable, although kasprintf() (or its
> devm_ variant) might make matters a little simpler.

What prevents us to create a field in uart_port (uart8250_port?) where
we put the uart_port_name() for future use as long as uart_port is
alive?


-- 
With Best Regards,
Andy Shevchenko