linux-kernel - Re: Re: [PATCH V6] serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers

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Message-ID: <535A226E.7000608@hitachi.com>
Date:	Fri, 25 Apr 2014 17:53:02 +0900
From:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Stephen Warren <swarren@...dia.com>,
	Alan <gnomes@...rguk.ukuu.org.uk>,
	Jingoo Han <jg1.han@...sung.com>, linux-kernel@...r.kernel.org,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	linux-serial@...r.kernel.org, yrl.pp-manager.tt@...achi.com,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Aaron Sierra <asierra@...-inc.com>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: Re: [PATCH V6] serial/uart/8250: Add tunable RX interrupt
 trigger I/F of FIFO buffers

Hi Greg,

Thank you for your review.

(2014/04/25 8:11), Greg Kroah-Hartman wrote:
> On Thu, Apr 17, 2014 at 03:06:44PM +0900, Yoshihiro YUNOMAE wrote:
[snip]
>> +static DEVICE_ATTR(rx_int_trig, S_IRUSR | S_IWUSR | S_IRGRP,
>> +		   serial8250_get_attr_rx_int_trig,
>> +		   serial8250_set_attr_rx_int_trig);
>> +
>
> As you are adding a new sysfs attribute, you have to add a
> Documentation/ABI/ entry as well.

I added this attribute to /sys/dev/char/*, so the documentation
may be sysfs-dev. However, any other attributes are not written
at all. Should I add this description to it or is there another
file?

>> +static struct attribute *serial8250_dev_attrs[] = {
>> +	&dev_attr_rx_int_trig.attr,
>> +	NULL,
>> +	};
>> +
>> +static struct attribute_group serial8250_dev_attr_group = {
>> +	.attrs = serial8250_dev_attrs,
>> +	};
>
> What's wrong with the macro to create a group?

I'll explain about this below.

>> +
>> +static void register_dev_spec_attr_grp(struct uart_8250_port *up)
>> +{
>> +	const struct serial8250_config *conf_type = &uart_config[up->port.type];
>> +
>> +	if (conf_type->rxtrig_bytes[0])
>> +		up->port.dev_spec_attr_group = &serial8250_dev_attr_group;
>> +}
>> +
>>   static void serial8250_config_port(struct uart_port *port, int flags)
>>   {
>>   	struct uart_8250_port *up =
>> @@ -2708,6 +2848,9 @@ static void serial8250_config_port(struct uart_port *port, int flags)
>>   	if ((port->type == PORT_XR17V35X) ||
>>   	   (port->type == PORT_XR17D15X))
>>   		port->handle_irq = exar_handle_irq;
>> +
>> +	register_dev_spec_attr_grp(up);
>> +	up->fcr = uart_config[up->port.type].fcr;
>>   }
>>
>>   static int
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index 2cf5649..41ac44b 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -2548,15 +2548,16 @@ static struct attribute *tty_dev_attrs[] = {
>>   	NULL,
>>   	};
>>
>> -static const struct attribute_group tty_dev_attr_group = {
>> +static struct attribute_group tty_dev_attr_group = {
>>   	.attrs = tty_dev_attrs,
>>   	};
>>
>> -static const struct attribute_group *tty_dev_attr_groups[] = {
>> -	&tty_dev_attr_group,
>> -	NULL
>> -	};
>> -
>> +static void make_uport_attr_grps(struct uart_port *uport)
>> +{
>> +	uport->attr_grps[0] = &tty_dev_attr_group;
>> +	if (uport->dev_spec_attr_group)
>> +		uport->attr_grps[1] = uport->dev_spec_attr_group;
>> +}
>>
>>   /**
>>    *	uart_add_one_port - attach a driver-defined port structure
>> @@ -2607,12 +2608,15 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
>>
>>   	uart_configure_port(drv, state, uport);
>>
>> +	make_uport_attr_grps(uport);
>> +
>>   	/*
>>   	 * Register the port whether it's detected or not.  This allows
>>   	 * setserial to be used to alter this port's parameters.
>>   	 */
>>   	tty_dev = tty_port_register_device_attr(port, drv->tty_driver,
>> -			uport->line, uport->dev, port, tty_dev_attr_groups);
>> +			uport->line, uport->dev, port,
>> +			(const struct attribute_group **)uport->attr_grps);
>
> If you have to cast that hard, something is wrong here, why are you
> doing that?

The attribute group in serial layer was defined as constant
because serial layer has only common sysfs I/F. However, I want to
change sysfs I/F for specific devices. So, I deleted 'const' from the
definition of the attribute group in serial layer in order to make the
attribute group be changeable. On the other hand, to pass the attribute
group to tty layer, the group must be const because the 5th variable of
tty_port_register_device_attr() is an attribute group with 'const', so
I implemented like this. Although I investigated again,
tty_port_register_device_attr() is used only here, and
tty_register_device_attr() called by the function is called from 2
locations (the one of them passes NULL in the 5th variable).
Therefore, we can delete 'const' for those functions, I think.
How do you think about this?

Thank you,
Yoshihiro YUNOMAE

-- 
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@...achi.com


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