linux-kernel - Re: [PATCH 1/3] i3c: master: Add inline i3c_master_readsl and i3c_master

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Message-ID: <aFWrSHg2M1lq8kGt@lizhi-Precision-Tower-5810>
Date: Fri, 20 Jun 2025 14:41:12 -0400
From: Frank Li <Frank.li@....com>
To: Jorge Marques <jorge.marques@...log.com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Przemysław Gaj <pgaj@...ence.com>,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] i3c: master: Add inline i3c_master_readsl and
 i3c_master_writesl

On Fri, Jun 20, 2025 at 06:54:59PM +0200, Jorge Marques wrote:
> The i3c abstraction excepts u8 buffers, but some controllers have a bus
> width of 32-bits and don't support flagging valid bytes, so it is
> required to read/write long words and to use memcpy on the remainder of
> the number of bytes by 32-bits to not write/read outside the buffer
> bounds.
>
> Signed-off-by: Jorge Marques <jorge.marques@...log.com>
> ---
>  include/linux/i3c/master.h | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>
> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
> index c67922ece617d6320c0c7e4838c2e7edda8c19f5..11401f2acb42e4d3a60df33b7c794d8a0360cdc2 100644
> --- a/include/linux/i3c/master.h
> +++ b/include/linux/i3c/master.h

suggest move to drivers/i3c/internals.h becaue only master drivers use it.

> @@ -674,6 +674,42 @@ i3c_master_get_bus(struct i3c_master_controller *master)
>  	return &master->bus;
>  }
>
> +/**
> + * i3c_master_writesl- Write bytes to long memory region from byte array
> + * @addr: Register to write to
> + * @bytes: Pointer to the data bytes to write
> + * @nbytes: Number of bytes to write
> + */
> +static inline void i3c_master_writesl(void __iomem *addr, const u8 *bytes,
> +				      int nbytes)

const void *bytes

> +{
> +writesl(addr, bytes, nbytes / 4);

fix indention

Frank

> +	if (nbytes & 3) {
> +		u32 tmp = 0;
> +
> +		memcpy(&tmp, bytes + (nbytes & ~3), nbytes & 3);
> +		writel(tmp, addr);
> +	}
> +}
> +
> +/**
> + * i3c_master_readsl - Read bytes from long memory region to byte array
> + * @addr: Register to read from
> + * @bytes: Pointer to the buffer to store read bytes
> + * @nbytes: Number of bytes to read
> + */
> +static inline void i3c_master_readsl(const void __iomem *addr, u8 *bytes,
> +				     int nbytes)
> +{
> +readsl(addr, bytes, nbytes / 4);
> +	if (nbytes & 3) {
> +		u32 tmp;
> +
> +		tmp = readl(addr);
> +		memcpy(bytes + (nbytes & ~3), &tmp, nbytes & 3);
> +	}
> +}
> +
>  struct i3c_generic_ibi_pool;
>
>  struct i3c_generic_ibi_pool *
>
> --
> 2.49.0
>
>