linux-kernel - Re: [PATCH] firmware: arm_scmi: Use {get,put}_unaligned

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Message-ID: <1565184971.5048.8.camel@pengutronix.de>
Date:   Wed, 07 Aug 2019 15:36:11 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Sudeep Holla <sudeep.holla@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] firmware: arm_scmi: Use {get,put}_unaligned_le32
 accessors

Hi Sudeep,

On Wed, 2019-08-07 at 14:00 +0100, Sudeep Holla wrote:
> Instead of type-casting the {tx,rx}.buf all over the place while
> accessing them to read/write __le32 from/to the firmware, let's use
> the nice existing {get,put}_unaligned_le32 accessors to hide all the
> type cast ugliness.
> 
> Suggested-by: Philipp Zabel <p.zabel@...gutronix.de>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  drivers/firmware/arm_scmi/base.c    |  2 +-
>  drivers/firmware/arm_scmi/clock.c   | 10 ++++------
>  drivers/firmware/arm_scmi/common.h  |  2 ++
>  drivers/firmware/arm_scmi/perf.c    |  8 ++++----
>  drivers/firmware/arm_scmi/power.c   |  6 +++---
>  drivers/firmware/arm_scmi/reset.c   |  2 +-
>  drivers/firmware/arm_scmi/sensors.c | 12 +++++-------
>  7 files changed, 20 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c
> index 204390297f4b..f804e8af6521 100644
> --- a/drivers/firmware/arm_scmi/base.c
> +++ b/drivers/firmware/arm_scmi/base.c
[...]
> @@ -204,14 +204,12 @@ scmi_clock_rate_get(const struct scmi_handle *handle, u32 clk_id, u64 *value)
>  	if (ret)
>  		return ret;
>  
> -	*(__le32 *)t->tx.buf = cpu_to_le32(clk_id);
> +	put_unaligned_le32(clk_id, t->tx.buf);
>  
>  	ret = scmi_do_xfer(handle, t);
>  	if (!ret) {
> -		__le32 *pval = t->rx.buf;
> -
> -		*value = le32_to_cpu(*pval);
> -		*value |= (u64)le32_to_cpu(*(pval + 1)) << 32;
> +		*value = get_unaligned_le32(t->rx.buf);
> +		*value |= (u64)get_unaligned_le32(t->rx.buf + 1) << 32;

Isn't t->rx.buf a void pointer? If I am not mistaken, you'd either have
to keep the pval local variables, or cast to (__le32 *) before doing
pointer arithmetic.

regards
Philipp