linux-kernel - Re: [V4, 2/3] powerpc/opal: Add #define to get rc from an ASYNC_COMP opal

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Date:	Tue, 28 Jun 2016 21:58:28 +1000 (AEST)
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Suraj Jitindar Singh <sjitindarsingh@...il.com>,
	linuxppc-dev@...ts.ozlabs.org
Cc:	robh@...nel.org, arnd@...db.de, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, paulus@...ba.org,
	sjitindarsingh@...il.com
Subject: Re: [V4, 2/3] powerpc/opal: Add #define to get rc from an ASYNC_COMP opal_msg

On Tue, 2016-28-06 at 04:40:56 UTC, Suraj Jitindar Singh wrote:
> An opal_msg of type OPAL_MSG_ASYNC_COMP contains the return code in the
> params[1] struct member. However this isn't intuitive or obvious when
> reading the code and requires that a user look at the skiboot
> documentation or opal-api.h to verify this.
> 
> Add a #define to get the return code from an opal_msg and update call
> sites accordingly.

Thanks for cleaning this up.

Two gripes though :)

>  arch/powerpc/include/asm/opal-api.h            | 4 ++++

opal-api.h is supposed to be a subset of the skiboot version.

So something like this should go in the kernel's opal.h, which has all the
kernel prototypes etc. which aren't part of the OPAL API. I think this routine
should fall under that.

> diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
> index 9bb8ddf..7433cf0 100644
> --- a/arch/powerpc/include/asm/opal-api.h
> +++ b/arch/powerpc/include/asm/opal-api.h
> @@ -387,6 +387,10 @@ struct opal_msg {
>  	__be64 params[8];
>  };
>  
> +#define GET_OPAL_MSG_ASYNC_COMP_RC(msg)	(msg.msg_type == OPAL_MSG_ASYNC_COMP ? \
> +					be64_to_cpu(msg.params[1]) : \
> +					OPAL_PARAMETER)
> +

You forgot the 7th commandment!

 "Never use a #define when a static inline would work"

:)

A few reasons:
  - it's less shouty.
  - you get type checking.
  - you don't have to wrap lines with \
    etc.

cheers