linux-kernel - Re: [PATCH 1/1] [RFC] uartclk from serial

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Message-ID: <CAEB7QLCgUJzq+7nqDoBLp8hRpKXAxhajPFnMEZ82MfzesUqZ6A@mail.gmail.com>
Date:	Wed, 15 Aug 2012 19:09:05 +0200
From:	Tomas Hlavacek <tmshlvck@...il.com>
To:	Marek Vasut <marek.vasut@...il.com>
Cc:	gregkh@...uxfoundation.org, alan@...ux.intel.com,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] [RFC] uartclk from serial_core exposed to sysfs

Hello Marek,

On Tue, Aug 14, 2012 at 2:50 PM, Marek Vasut <marek.vasut@...il.com> wrote:
> Dear Tomas Hlavacek,
>
>> +static ssize_t get_attr_uartclk(struct device *dev,
>> +             struct device_attribute *attr, char *buf)
>> +{
>> +     int ret;
>> +
>> +     struct uart_state *state = (struct uart_state *)(dev_get_drvdata(dev));
>
> You don't need this cast here.

Yes, you are right. Thanks.

>
>> +     mutex_lock(&state->port.mutex);
>> +     ret = snprintf(buf, PAGE_SIZE, "%d\n", state->uart_port->uartclk);
>
> Do you really need such a large buffer (PAGE_SIZE) ?

Well no, but I believe that I get the buffer of length equal to
PAGE_SIZE anyway. Documentation/filesystems/sysfs.txt says so on line
179.

>
>> +     mutex_unlock(&state->port.mutex);
>> +     return ret;
>> +}
>> +
>> +static ssize_t set_attr_uartclk(struct device *dev,
>> +             struct device_attribute *attr, const char *buf, size_t count)
>> +{
>> +     struct uart_state *state = (struct uart_state *)(dev_get_drvdata(dev));
>> +     unsigned int val;
>> +     int ret;
>> +
>> +     ret = kstrtouint(buf, 10, &val);
>> +     if (ret)
>> +             return ret;
>> +
>> +     mutex_lock(&state->port.mutex);
>> +
>> +     /*
>> +      * Check value: baud_base has to be more than 9600
>> +      * and uartclock = baud_base * 16 .
>> +      */
>> +     if (val >= 153600)
>> +             state->uart_port->uartclk = val;
>
> This magic value here would use some documentation.

OK. Do you think this would be sufficient comment?:

/*
 * Check value: baud_base does not make sense to be set below 9600
 * and since uartclock = (baud_base * 16) it has to be equal or greater than
 * 9600 * 16 = 153600.
 */

PATCHv2 follows.

Tomas


-- 
Tomáš Hlaváček <tmshlvck@...il.com>
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