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

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Message-ID: <20170327124105.rapd3sd3zjf3um2x@dell>
Date:   Mon, 27 Mar 2017 13:41:05 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] mfd: core: Preserve PLATFORM_DEVID_NONE

On Sun, 26 Mar 2017, Andy Shevchenko wrote:

> 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.

I'd be happy to review any proposal you put forward. :)

> > > 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;
> > > > 
> > > > 
> > 
> > 
> 

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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