linux-kernel - Re: [PATCH v2] serdev: Replace serdev_device_write_buf with serdev_device

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Message-ID: <CAHp75Vc4HPSnw6XtUO3Sq3hMQFtaGvK2TmvnWX2q5B=ixBjiig@mail.gmail.com>
Date:   Wed, 29 Mar 2017 17:43:53 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     Rob Herring <robh@...nel.org>, Chris Healy <cphealy@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] serdev: Replace serdev_device_write_buf with serdev_device_write

On Wed, Mar 29, 2017 at 5:16 PM, Andrey Smirnov
<andrew.smirnov@...il.com> wrote:
> On Tue, Mar 28, 2017 at 10:07 AM, Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
>> On Tue, Mar 28, 2017 at 7:01 PM, Andrey Smirnov
>> <andrew.smirnov@...il.com> wrote:

>> So, what I would see if no one objects is patch series of two:
>> 1) introduction of new API
>> 2) removing old one.
>>
>> It will benefit for easier review and any potential code anthropologist.
>>
>
> Second version of the patch preserves the old API an just
> re-implements it in terms of a new one. I am not sure I see the
> benefit in splitting it into two patches, but I'll leave it up to Rob
> to decide.

Sure. At least I posted benefits I see from splitting.

+ bisectability (in case we have to revert your new API by some reason
it will be easier, hope will be not the case, though...)

>>> +       } while (count &&
>>> +                (timeout = wait_for_completion_timeout(&serdev->write_comp,
>>> +                                                       timeout)));
>>
>> So, would it be better to support interrupts here and return a
>> corresponding error code to the user?
>>
>
> I don't have a use-case for that and as far as I can tell, neither SPI
> nor I2C slave device API offer such functionality universally, so I am
> inclined to say no. Since the change from wait_for_completion to
> wait_for_completion_timeout was made per Rob's request, I'd leave it
> up to him to decided about this change as well.

OK.

>> Besides that question, readability might be better if you use
>> temporary variable and pack above on one line:
>>
>> unsigned long to = timeout;
>>
>> } while (count && (to = ...(to)));
>>
>
> Even if you shorten 'timeout' to 'to', formatted as a single line,
> it'd still exceed line length limitations.

How many? If we are talking about 2-3 characters, that's okay to leave
them on one line.

>>> + * @write_lock Mutext used to esure exclusive access to the bus when
>>> + *             writing data with serdev_device_write()
>>
>> checkpatch.pl has integrated spellchecker AFAIU.
>
> My bad, forgot to enable it as a git hook, will fix.
>
>> Moreover, can you try harder to make that description shorter?
>>
>
> I am all ears for suggestions alternative phrasing, otherwise, no,
> that's about as hard as I try.

First of all, "used to" is (closer) equivalent to was.
Second, Mutex is one letter longer than Lock (here is important that
is just a kind of lock).
Third, "exclusive" is implied by Mutex / Lock word.
Fourth, "access to the bus when writing data" too verbose.

So, my suggestion is (two variants):
a) "Lock to serialize bus access when writing data."
b) "Lock to serialize access when writing data with serdev_device_write()."

-- 
With Best Regards,
Andy Shevchenko