Re: [PATCHv7 1/4] pwm: Add Freescale FTM PWM driver support

[Thierry Reding]

On Tue, Dec 17, 2013 at 01:04:35PM +0000, Russell King - ARM Linux wrote:
> On Tue, Dec 17, 2013 at 01:54:35PM +0100, Tomasz Figa wrote:
> > On Tuesday 17 of December 2013 13:45:06 Thierry Reding wrote:
> > > I fail to see how that would eliminate the problem with the types. That
> > > said I don't actually see sparse complaining about any type mismatches.
> > > That's probably because the various macros implicitly cast to u32.
> > 
> > Well, in BE variant you would read the register using __raw_readl() into
> > a __be32 and then get an u32 from be32_to_cpu() and return it. Similarly
> > for writes
> 
> __raw_readl() returns a u32, so you'll get a warning trying to assign a
> u32 to a __be32.

If sparse doesn't complain about the original code here, does that mean
we have a bug that should be fixed?

> We do have ioread32() and ioread32be() which do the appropriate conversion,
> as well as the write versions too.  They both include the barrier if you're
> overly concerned about that.

A few years ago GregKH commented in response to a patch that ioread*()
weren't supposed to be used for memory-mapped only devices. The original
purpose apparently was to allow drivers to work with both I/O and
memory-mapped devices.

Thierry

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