[i2c] [PATCH] of/i2c: don't pass -1 to irq_dispose_mapping, otherwise kernel will oops

[Wolfram Sang]

On Fri, Jul 11, 2008 at 11:15:02PM +0400, Anton Vorontsov wrote:

> > Nope, it was a bug in the i2c documentation fixed recently:
> 
> Nope? I'm looking into i2c-core.c:
> 
> .. i2c_new_device(...)
> {
> 	client->irq = info->irq;
> 
> Core will blindly pass irq, so clients should ensure that irq contains
> correct value. And as far as there is no common scheme of checking that
> "there is no irq specified", the most safe option is -1.

I wonder if -1 is really the safest; even kernel functions related to
irqs are not consistent if "irq" is int or unsigned int. So, -1 could
cause subtle signedness defects.

The whole "no irq" mess really needs to be cleared generally. It just
disturbed me that i2c_core was imposing -1, whilst some other subsystem
may have chosen 0. IMHO, subsystems like i2c should pass irqs
transparently. This is why I submitted the patch for i2c documentation.

All the best,

   Wolfram

-- 
  Dipl.-Ing. Wolfram Sang | http://www.pengutronix.de
 Pengutronix - Linux Solutions for Science and Industry
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