Re: [PATCH V3 5/9] tracing/trace: Add a generic function to read/write u64 values from tracefs

From: Daniel Bristot de Oliveira <bristot@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Phil Auld <pauld@redhat.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Kate Carcia <kcarcia@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Alexandre Chartre <alexandre.chartre@oracle.com>,
	Clark Willaims <williams@redhat.com>,
	John Kacur <jkacur@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH V3 5/9] tracing/trace: Add a generic function to read/write u64 values from tracefs
Date: Fri, 4 Jun 2021 18:34:02 +0200	[thread overview]
Message-ID: <59726959-bc86-8760-580d-3d4ceee45dad@redhat.com> (raw)
In-Reply-To: <20210604121802.192caa07@oasis.local.home>

On 6/4/21 6:18 PM, Steven Rostedt wrote:
> On Fri, 4 Jun 2021 18:05:06 +0200
> Daniel Bristot de Oliveira <bristot@redhat.com> wrote:
> 
>>
>> The reason for this patch is that hwlat, osnoise, and timerlat have "u64 config"
>> options that are read/write via tracefs "files." In the previous version, I had
>> multiple functions doing basically the same thing:
>>
>> A write function that:
>> 	read a u64 from user-space
>> 	get a lock,
>> 	check for min/max acceptable values
>> 		save the value
>> 	release the lock.
>>
>> and a read function that:
>> 	write the config value to the "read" buffer.
>>
>> And so, I tried to come up with a way to avoid code duplication.
>>
>> question: are only the names that are bad? (I agree that they are bad) or do you
>> think that the overall idea is bad? :-)
>>
>> Suggestions?
> 
> I don't think the overall idea is bad, if it is what I think you are
> doing. I just don't believe you articulated what you are doing.

I see!

> It has nothing to do with 64 bit reads and writes, but instead has to
> do with reading and writing values that depend on each other for what
> is acceptable.

yeah, that is a better (starting point for an) explanation.

> Perhaps have it called trace_min_max_write() and trace_min_max_read(),
> and document what it is used for.

I will do that!

-- Daniel

> -- Steve
> 