linux-kernel - Re: [PATCH 4/4] printk: Add a device attribute for the per-console loglevel

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Date:   Mon, 4 Mar 2019 17:06:30 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Calvin Owens <calvinowens@...com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH 4/4] printk: Add a device attribute for the per-console
 loglevel

On (03/01/19 16:48), Calvin Owens wrote:
> +static ssize_t loglevel_store(struct device *dev, struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	struct console *con = container_of(dev, struct console, dev);
> +	ssize_t ret;
> +	int tmp;
> +
> +	ret = kstrtoint(buf, 10, &tmp);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (tmp < LOGLEVEL_EMERG)
> +		return -ERANGE;
> +
> +	/*
> +	 * Mimic the behavior of /dev/kmsg with respect to minimum_loglevel.
> +	 */
> +	if (tmp < minimum_console_loglevel)
> +		tmp = minimum_console_loglevel;
> +
> +	con->level = tmp;
> +	return ret;
> +}
> +
> +static DEVICE_ATTR_RW(loglevel);
> +
> +static struct attribute *console_sysfs_attrs[] = {
> +	&dev_attr_loglevel.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(console_sysfs);
> +
>  static struct bus_type console_subsys = {
>  	.name = "console",
> +	.dev_groups = console_sysfs_groups,
>  };

Do we really need to change this dynamically? Console options are
traditionally static (boot param or DT). Can we also be happy with
the static per-console loglevel?

	-ss