linux-kernel - Re: Converting DEVICE_ATTR to DEVICE_ATTR_{RO,RW,WO} and changing function names at the same time

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Date:   Thu, 22 Dec 2016 16:45:45 +0100 (CET)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Guenter Roeck <linux@...ck-us.net>
cc:     cocci@...teme.lip6.fr, Greg KH <gregkh@...uxfoundation.org>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Converting DEVICE_ATTR to DEVICE_ATTR_{RO,RW,WO} and changing
 function names at the same time



On Thu, 22 Dec 2016, Guenter Roeck wrote:

> On 12/22/2016 04:29 AM, Julia Lawall wrote:
> >
> >
> > On Wed, 21 Dec 2016, Guenter Roeck wrote:
> >
> > > Hi Julia,
> > >
> > > On Wed, Dec 21, 2016 at 08:39:38PM +0100, Julia Lawall wrote:
> > > >
> > > >
> > > > On Wed, 21 Dec 2016, Guenter Roeck wrote:
> > > >
> > > > > Hi Julia,
> > > > >
> > > > > On Wed, Dec 21, 2016 at 03:05:37PM +0100, Julia Lawall wrote:
> > > > > > A solution is below: the semantic patch, an explanation of the
> > > > > > semantic
> > > > > > patch, and the results.  I have only tried to compile the results
> > > > > > (make
> > > > > > drivers/hwmon/).  Two affected files were not considered for
> > > > > > compilation:
> > > > > >
> > > > > > drivers/hwmon/vexpress-hwmon.o
> > > > > > drivers/hwmon/jz4740-hwmon.o
> > >
> > > I compile tested those two patches. If possible please drop
> > > vexpress-hwmon.c
> > > from the patch series; the changes in that file don't add any value.
> > >
> > > I compile tested all files, and reviewed the patch. It all looks good.
> > > Please submit the series.
> > >
> > > Again, thanks a lot for your help!
> >
> > I have sent the patches.  I adjusted the semantic patch so that the
> > indentation of function parameters/arguments would only change if the
> > length of the function name changes.
> >
> > Do you think this could be of more general interest in the Linux kernel?
> > Since the semantic patch works pretty well, I could add it to the
> > scripts/coccinelle directory?  Previously, however, I got some negative
> > feedback about this change, because people felt that the new names hid the
> > actual behavior, so I didn't pursue it.
> >
>
> I do think it would add a lot of value, if for nothing else as an excellent
> example
> of what can be done with coccinelle.
>
> I actually liked the name changes. I think it is a good idea if the function
> name
> reflects the sysfs attribute it serves (isn't that exactly what it does, ie
> its
> behavior ?). But, as you have experienced, some people inadvertently did not
> like
> it. Given that, I am not sure if it is worth adding it to the kernel source
> tree.
> Maybe you could submit it as RFC so it is at least on record.
>
> Anyway, for SENSOR_DEVICE_ATTR(), I'll have to be a bit more flexible since
> the function _will_ be reused. I'll need something like
> 	SENSOR_DEVICE_ATTR_{RO,RW,WO}(attr, func, param)

Chosen at random,

static SENSOR_DEVICE_ATTR_2(sf2_point4_fan1, S_IRUGO | S_IWUSR,
                        show_sf2_point, store_sf2_point, 4, 1);

should become

static SENSOR_DEVICE_ATTR_2_RW(sf2_point4_fan1, sf2_point, 4, 1); ?

And the functions should be renamed with show and store at the end?

> Maybe Greg would be open to something like
> DEVICE_ATTR_FUNC_{RO,RW,WO}(attr,func)
> to accommodate the "I want my own function name" crowd ? That would also solve
> the case where the function is reused for multiple attributes.

Actually, it was the DEVICE_ATTR_{RO,RW,WO} that wasn't liked.  It doesn't
show the exact permission numbers.  The fact that not all DEVICE_ATTR uses
can be changed due to function reuse is awkward, though.  Greg, do you
have any thoughts about that?

Currently, there are around 1100 calls to DEVICE_ATTR_{RO,RW,WO}.

julia