linux-kernel - Re: [RFC PATCH 01/06] input/rmi4: Public header and documentation

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Date:	Tue, 23 Oct 2012 16:18:25 -0700
From:	Christopher Heiny <cheiny@...aptics.com>
To:	Linus Walleij <linus.walleij@...aro.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jean Delvare <khali@...ux-fr.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Input <linux-input@...r.kernel.org>,
	Allie Xiong <axiong@...aptics.com>,
	Vivian Ly <vly@...aptics.com>,
	Daniel Rosenberg <daniel.rosenberg@...aptics.com>,
	Joerie de Gram <j.de.gram@...il.com>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Naveen Kumar Gaddipati <naveen.gaddipati@...ricsson.com>,
	Alexandra Chin <alexandra.chin@...synaptics.com>
Subject: Re: [RFC PATCH 01/06] input/rmi4: Public header and documentation

On 10/11/2012 08:32 AM, Linus Walleij wrote:
> On Thu, Oct 11, 2012 at 5:41 AM, Christopher Heiny <Cheiny@...aptics.com> wrote:
>> Linus Walleij wrote:
>
>>> But please use arithmetic operators (I think I said this on the last
>>> review):
>>>
>>> dest[0] = src & 0xFF;
>>> dest[1] = src >> 8;
>>>
>>> Doing it the above way makes artithmetic look like maths, and it isn't.
>>> Besides it's done this way in most parts of the kernel and we're
>>> familiar with it.
>>
>> Yes, you mentioned it previously.  I'm somewhat paranoid, though, and
>> don't trust the shift/mask method to work correctly on big-endian
>> machines.  If the shifts can be relied on to behave (I'm guessing the
>> answer is "yes", since you say this idiom is used widely in the
>> kernel), then I'll change it.
>
> If the behaviour was not consistent across different endianness
> it would not be part of the C language specification...
>
> << means shift left in the accumulator or whatever you have.
> It will work the same no matter how bits are laid out in
> memory.

OK, after reviewing the spec I'll accept that.  We'll make the change.

>>>> +static inline ssize_t rmi_store_error(struct device *dev,
>>>> +                       struct device_attribute *attr,
>>>> +                       const char *buf, size_t count)
>>>> +{
>>>> +       dev_warn(dev,
>>>> +                "WARNING: Attempt to write %d characters to read-only
>>>> attribute %s.", +               count, attr->attr.name);
>>>> +       return -EPERM;
>>>> +}
>>>
>>> Here it looks like you're hiding a lot of stuff that should be dev_warn()?
>>> Consider my earlier point about dynamic debug.
>>
>> In previous patch submissions, we always used these warning functions.
>> But in the feedback on those patches, we were asked to just make
>> sysfs show/store NULL if the attribute is write/read only.  However,
>> during their development process, our customers want to see the
>> warnings if the attributes are accessed incorrectly.  So we made
>> these warnings a debug option.
>
> See Dmitry's comment ...
>
> Basically my stance is that you should not lower yourself to the
> level of others not getting the point of your technical solution
> by making unelegant compromises, what
> you should do is to bring them up to your level so they
> understand that your solution is elegant.
>
> Maybe a bit utopist I know...

What's the old saying?  "I want to live in Theory.  Everything is always 
so nice there..."  :-)

Anyway, see my reply to Dmitry a bit ago.  These are no longer needed, 
so we'll drop them.
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