Re: [RCF PATCH,v2,2/2] pwm: imx: Configure output to GPIO in disabled state

Uwe Kleine-König
2018-10-14T20:25:06Z

Hello,

On Fri, Oct 12, 2018 at 06:08:54PM +0200, Uwe Kleine-König wrote:
> > >> + if (PTR_ERR(imx_chip->pwm_gpiod) == -EPROBE_DEFER) {
> > >
> > > You must not use PTR_ERR on a value that might not contain an error
> > > pointer.
> >
> > OK, thank you for valuable info.
> > So it seems like the I2C folks are in troubles as well:
> >
> > https://elixir.bootlin.com/linux/latest/source/drivers/i2c/busses/i2c-imx.c#L996
>
> correct. I cannot find this documented though.

I found in LDD3[1], chapter 11 on page 295:

If you need the actual error code, it can be extracted with:

long PTR_ERR(const void *ptr);

You should use PTR_ERR only on a value for which IS_ERR returns a true
value; any other value is a valid pointer.

That is probably where I have my claim from. There is no further
explanation though, so I'll post a patch adding a comment to the
definition of PTR_ERR to find out if there is a relevant reason.

Best regards
Uwe

[1] https://lwn.net/Kernel/LDD3/

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