linux-kernel - Re: [PATCH] pinctrl: zynq: Use define directive for PIN_CONFIG_IO

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Message-ID: <68ae935a-aec3-915c-bfe6-d69bfb93d702@xilinx.com>
Date:   Wed, 7 Nov 2018 09:46:12 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>
CC:     Michal Simek <michal.simek@...inx.com>,
        <linux-gpio@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] pinctrl: zynq: Use define directive for
 PIN_CONFIG_IO_STANDARD

On 01. 11. 18 1:57, Nathan Chancellor wrote:
> Clang warns when one enumerated type is implicitly converted to another:
> 
> drivers/pinctrl/pinctrl-zynq.c:985:18: warning: implicit conversion from
> enumeration type 'enum zynq_pin_config_param' to different enumeration
> type 'enum pin_config_param' [-Wenum-conversion]
>         {"io-standard", PIN_CONFIG_IOSTANDARD, zynq_iostd_lvcmos18},
>         ~               ^~~~~~~~~~~~~~~~~~~~~
> drivers/pinctrl/pinctrl-zynq.c:990:16: warning: implicit conversion from
> enumeration type 'enum zynq_pin_config_param' to different enumeration
> type 'enum pin_config_param' [-Wenum-conversion]
>         = { PCONFDUMP(PIN_CONFIG_IOSTANDARD, "IO-standard", NULL, true),
>             ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/pinctrl/pinconf-generic.h:163:11: note: expanded from
> macro 'PCONFDUMP'
>         .param = a, .display = b, .format = c, .has_arg = d     \
>                  ^
> 2 warnings generated.

This is interesting. I have never tried to use llvm for building the
kernel. Do you have any description how this can be done?


> 
> It is expected that pinctrl drivers can extend pin_config_param because
> of the gap between PIN_CONFIG_END and PIN_CONFIG_MAX so this conversion
> isn't an issue. Most drivers that take advantage of this define the
> PIN_CONFIG variables as constants, rather than enumerated values. Do the
> same thing here so that Clang no longer warns.
> 
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  drivers/pinctrl/pinctrl-zynq.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/pinctrl/pinctrl-zynq.c b/drivers/pinctrl/pinctrl-zynq.c
> index a0daf27042bd..57046c221756 100644
> --- a/drivers/pinctrl/pinctrl-zynq.c
> +++ b/drivers/pinctrl/pinctrl-zynq.c
> @@ -972,14 +972,11 @@ enum zynq_io_standards {
>  };
>  
>  /**
> - * enum zynq_pin_config_param - possible pin configuration parameters

This is wrong. kernel-doc is reporting issue with it.

drivers/pinctrl/pinctrl-zynq.c:975: warning: Cannot understand  *
@PIN_CONFIG_IOSTANDARD: if the pin can select an IO standard, the
argument to
 on line 975 - I thought it was a doc line
1 warnings


>   * @PIN_CONFIG_IOSTANDARD: if the pin can select an IO standard, the argument to
>   *	this parameter (on a custom format) tells the driver which alternative
>   *	IO standard to use.
>   */
> -enum zynq_pin_config_param {
> -	PIN_CONFIG_IOSTANDARD = PIN_CONFIG_END + 1,
> -};
> +#define PIN_CONFIG_IOSTANDARD		(PIN_CONFIG_END + 1)
>  
>  static const struct pinconf_generic_params zynq_dt_params[] = {
>  	{"io-standard", PIN_CONFIG_IOSTANDARD, zynq_iostd_lvcmos18},
> 

This change is fine.

Thanks,
Michal