netdev - Re: [PATCH net-next 1/1] net: wwan: t7xx: Add port for modem logging

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Date:   Fri, 20 May 2022 11:01:31 -0700
From:   "moises.veleta" <moises.veleta@...ux.intel.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        johannes@...solutions.net, ryazanov.s.a@...il.com,
        loic.poulain@...aro.org, m.chetan.kumar@...el.com,
        chandrashekar.devegowda@...el.com, linuxwwan@...el.com,
        haijun.liu@...iatek.com, andriy.shevchenko@...ux.intel.com,
        ilpo.jarvinen@...ux.intel.com, ricardo.martinez@...ux.intel.com,
        sreehari.kancharla@...el.com, dinesh.sharma@...el.com
Subject: Re: [PATCH net-next 1/1] net: wwan: t7xx: Add port for modem logging


On 5/20/22 10:48, Jakub Kicinski wrote:
> On Fri, 20 May 2022 10:42:56 -0700 moises.veleta wrote:
>> On 5/20/22 10:37, Jakub Kicinski wrote:
>>> On Thu, 19 May 2022 11:27:03 -0700 Moises Veleta wrote:
>>>> +	ret = copy_from_user(skb_put(skb, actual_len), buf, actual_len);
>>>> +	if (ret) {
>>>> +		ret = -EFAULT;
>>>> +		goto err_out;
>>>> +	}
>>>> +
>>>> +	ret = t7xx_port_send_skb(port, skb, 0, 0);
>>>> +	if (ret)
>>>> +		goto err_out;
>>> We don't allow using debugfs to pass random data from user space
>>> to firmware in networking. You need to find another way.
>>
>> Can we use debugfs to send an "on" or "off" commands, wherein the driver
>> then sends special command sequences to the the firmware triggering the
>> modem logging on and off?
> On/off for all logging or for particular types of messages?
> If it's for all logging can't the act of opening the debugfs
> file be used as on "on" signal and closing as "off"?
>
> Where do the logging messages go?

It would be "on/off" for all logging.
Yes, opening the debugfs file can be used for "on" and closing for "off" 
without needing to use copy_from_user.

Logging messages would go to the relay interface file for consumption by 
a user application.