linux-kernel - Re: [Patch v3 1/2] arm: kernel: Add SMC structure parameter

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Date:   Thu, 19 Jan 2017 14:40:08 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Andy Gross <andy.gross@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, lorenzo.pieralisi@....com,
        linux-arm-msm@...r.kernel.org, will.deacon@....com,
        linux-kernel@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Kevin Hilman <khilman@...libre.com>
Subject: Re: [Patch v3 1/2] arm: kernel: Add SMC structure parameter

On Wed, Jan 11, 2017 at 04:31:57PM -0600, Andy Gross wrote:
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index b5abfda..3e28d08 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -72,19 +72,33 @@ struct arm_smccc_res {
>  };
>  
>  /**
> - * arm_smccc_smc() - make SMC calls
> + * struct arm_smccc_quirk - Contains quirk information
> + * id contains quirk identification
> + * state contains the quirk specific information

Given that this is a kerneldoc comment, it should really conform to the
kerneldoc requirements - see Documentation/kernel-doc-nano-HOWTO.txt:

/**
 * struct arm_smccc_quirk - Contains quirk information
 * @id: quirk identification
 * @state: the quirk specific information

> + */
> +struct arm_smccc_quirk {
> +	int	id;
> +	union {
> +		unsigned long a6;
> +	} state;
> +};
> +
> +/**
> + * __arm_smccc_smc() - make SMC calls
>   * @a0-a7: arguments passed in registers 0 to 7
>   * @res: result values from registers 0 to 3
> + * @quirk: optional quirk structure
>   *
>   * This function is used to make SMC calls following SMC Calling Convention.
>   * The content of the supplied param are copied to registers 0 to 7 prior
>   * to the SMC instruction. The return values are updated with the content
> - * from register 0 to 3 on return from the SMC instruction.
> + * from register 0 to 3 on return from the SMC instruction.  An optional
> + * quirk structure provides vendor specific behavior.

It's quite odd to have the result buried in the middle of arguments
passed to a function, but I guess for the sake of simplicity in the
assembly code that's what we need.

Also:

"@quirk points to an arm_smccc_quirk, or NULL when no quirks are required."

And... should this not be const?  Are we expecting anyone to modify
the quirk structure?

Thanks.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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