linux-kernel - Re: [PATCH v1] mfd: core: Preserve PLATFORM_DEVID

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Date:   Sun, 26 Mar 2017 15:53:35 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] mfd: core: Preserve PLATFORM_DEVID_NONE

On Fri, 2017-03-24 at 11:35 +0000, Lee Jones wrote:
> On Thu, 23 Mar 2017, Andy Shevchenko wrote:
> 
> > On Thu, 2017-03-23 at 11:21 +0000, Lee Jones wrote:
> > > On Thu, 16 Mar 2017, Andy Shevchenko wrote:
> > > 
> > > > There is a potential flaw if cell has id > 0 and is going to be
> > > > registered with PLATFORM_DEVID_NONE.
> > > > 
> > > > Ignore if PLATFORM_DEVID_NONE is supplied.
> > > 
> > > This is a substantial change to a pretty tried and tested piece of
> > > sub-system code.  Can you put some more meat on the bones in the
> > > commit log, and include examples.
> > 
> > Example in pseudo code:
> > 
> > cells = {
> >  [0] = { .id = 0, .name = "moduleX", },
> >  [1] = { .id = 1, .name = "moduleY", },
> >  [2] = { .id = 2, .name = "moduleZ", },
> >  ...
> > };
> > 
> > mfd_add_devices(..., PLATFORM_DEVID_NONE, cells, ARRAY_SIZE(cells),
> > ...);
> > 
> > Output (names of the devices in the drivers):
> > "moduleX"
> > "moduleY.0"
> > "moduleX.1"
> > 
> > Desired output:
> > "moduleX"
> > "moduleY"
> > "moduleZ"
> 
> Then what would be your reason for populating the 'id' attribute?

That's a gray area. If I remember correctly I come to above patch
through looking some incremental change.

I'm fine with no patch applied if this is documented somewhere,
otherwise we might update documentation to cover such cases explicitly.

> 
> > Is it by design?
> > 
> > > 
> > > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.co
> > > > m>
> > > > ---
> > > >  drivers/mfd/mfd-core.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> > > > index c57e407020f1..c9583f895058 100644
> > > > --- a/drivers/mfd/mfd-core.c
> > > > +++ b/drivers/mfd/mfd-core.c
> > > > @@ -149,7 +149,7 @@ static int mfd_add_device(struct device
> > > > *parent,
> > > > int id,
> > > >  	int platform_id;
> > > >  	int r;
> > > >  
> > > > -	if (id == PLATFORM_DEVID_AUTO)
> > > > +	if (id < 0)
> > > >  		platform_id = id;
> > > >  	else
> > > >  		platform_id = id + cell->id;
> > > 
> > > 
> 
> 

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy