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

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Message-ID: <20170316133632.GV21222@n2100.armlinux.org.uk>
Date:   Thu, 16 Mar 2017 13:36:32 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Vignesh R <vigneshr@...com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jisheng Zhang <jszhang@...vell.com>,
        linux-kernel@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-serial@...r.kernel.org, Jiri Slaby <jslaby@...e.com>,
        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 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.  8250 device names are always "ttyS"
plus a number, so 16 characters (including NULL terminator) should be
more than sufficient, and that's most likely true of all serial drivers.
(The longest device name I'm aware of is ttyAMA plus a small integer
for PL011 ports.)

-- 
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