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

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Date:   Mon, 20 Mar 2017 17:54:57 +0530
From:   Vignesh R <vigneshr@...com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>
CC:     Robin Murphy <robin.murphy@....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 Friday 17 March 2017 02:28 AM, Andy Shevchenko wrote:
> 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?
> 

Thanks for the suggestions. I will explore adding a field to uart_port
struct and provide a corresponding helper function uart_port_name() and
come up with a patch.


-- 
Regards
Vignesh