linux-kernel - Re: [PATCH v7 3/7] drivers/i2c: Add port structure to FSI algorithm

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Date:   Thu, 31 May 2018 09:21:25 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Eddie James <eajames@...ux.vnet.ibm.com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Edward A. James" <eajames@...ibm.com>
Subject: Re: [PATCH v7 3/7] drivers/i2c: Add port structure to FSI algorithm

On Thu, May 31, 2018 at 1:34 AM, Benjamin Herrenschmidt
<benh@...nel.crashing.org> wrote:
> On Thu, 2018-05-31 at 00:27 +0300, Andy Shevchenko wrote:
>> On Wed, May 30, 2018 at 6:47 PM, Eddie James <eajames@...ux.vnet.ibm.com> wrote:
>> > On 05/29/2018 06:19 PM, Andy Shevchenko wrote:
>> > > On Wed, May 30, 2018 at 1:24 AM, Eddie James <eajames@...ux.vnet.ibm.com>
>> > > wrote:

>> > > Isn't below somehow repeats of_i2c_register_devices() ?
>> > > Why not to use it?

>> > Because I need to assign all these port structure fields. Also looks like
>> > of_i2c_register_devices creates new devices; I just want an adapter for each
>> > port.
>>
>> Hmm... Wolfram, what is your opinion on this design?
>
> Andy, I don't understand your issue.
>
> of_i2c_register_devices() is about discovering the i2c devices below a
> given bus. This is not what is happening here.
>
> This is a driver for a master that supports multiple busses, so it the
> above loop creates all the busses.

My issue here, that it feels like a lot of duplication with existing approaches.
Though, it might be a right thing to do at the end. So, let's just
assume maintainer will give their point of view.

>> > > > +                       devm_kfree(dev, port);
>> > >
>> > > This hurts my eyes. Why?!
>> > What would you suggest instead?
>>
>> You even didn't wait for answer, why to ask then?
>
> Please stop being so rude.

OK.

>> Moreover, you didn't answer to my question. Why are you doing that
>> call implicitly?
>
> "implicitly" ? What's implicit here ? This is just pretty standard
> cleanup after failure, you are being very cryptic here.
>
> Please state precisely what it is you dislike with that code instead of
> expecting us to guess and being nasty about it. Eddie was a genuine
> question, he doesn't see what you think is "hurtful to the eyes" in the
> code you quoted.

In 99% cases when someone calls devm_kfree() it means wrong choice of
devm_k*alloc() in the first place.
So, with explanation given why it's done in this way I would rather
suggest to switch to plain k*alloc() / kfree().

Or do we really care about few hundreds of bytes wasted?

-- 
With Best Regards,
Andy Shevchenko