linux-kernel - Re: [PATCH] serial: amba-pl011: prefer dma_mapping

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Message-ID: <87a51ce68c.fsf@BLaptop.bootlin.com>
Date: Mon, 27 Oct 2025 16:04:19 +0100
From: Gregory CLEMENT <gregory.clement@...tlin.com>
To: Miaoqian Lin <linmq006@...il.com>, Russell King <linux@...linux.org.uk>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby
 <jirislaby@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
 <mingo@...nel.org>, Arnd Bergmann <arnd@...db.de>, Nam Cao
 <namcao@...utronix.de>, Toshiyuki Sato <fj6611ie@...jp.fujitsu.com>,
 Miroslav Ondra <ondra@...ter.cz>, linux-kernel@...r.kernel.org,
 linux-serial@...r.kernel.org
Cc: linmq006@...il.com, stable@...r.kernel.org
Subject: Re: [PATCH] serial: amba-pl011: prefer dma_mapping_error() over
 explicit address checking

Miaoqian Lin <linmq006@...il.com> writes:

> Check for returned DMA addresses using specialized dma_mapping_error()
> helper which is generally recommended for this purpose by
> Documentation/core-api/dma-api.rst:
>
>   "In some circumstances dma_map_single(), ...
> will fail to create a mapping. A driver can check for these errors
> by testing the returned DMA address with dma_mapping_error()."
>
> Found via static analysis and this is similar to commit fa0308134d26
> ("ALSA: memalloc: prefer dma_mapping_error() over explicit address checking")
>
> Fixes: 58ac1b379979 ("ARM: PL011: Fix DMA support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>


Reviewed-by: Gregory CLEMENT <gregory.clement@...tlin.com>

Thanks,

Gregory


> ---
>  drivers/tty/serial/amba-pl011.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> index 22939841b1de..7f17d288c807 100644
> --- a/drivers/tty/serial/amba-pl011.c
> +++ b/drivers/tty/serial/amba-pl011.c
> @@ -628,7 +628,7 @@ static int pl011_dma_tx_refill(struct uart_amba_port *uap)
>  	dmatx->len = count;
>  	dmatx->dma = dma_map_single(dma_dev->dev, dmatx->buf, count,
>  				    DMA_TO_DEVICE);
> -	if (dmatx->dma == DMA_MAPPING_ERROR) {
> +	if (dma_mapping_error(dma_dev->dev, dmatx->dma)) {
>  		uap->dmatx.queued = false;
>  		dev_dbg(uap->port.dev, "unable to map TX DMA\n");
>  		return -EBUSY;
> -- 
> 2.39.5 (Apple Git-154)
>

-- 
Grégory CLEMENT, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com