linux-kernel - Re: [PATCH] media: hantro: fix compatible string deprecation warning

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Message-ID: <0da188fa-efd8-62d0-2ea6-5a8e0c286cb5@arm.com>
Date:   Tue, 17 May 2022 17:46:35 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>,
        ezequiel@...guardiasur.com.ar, p.zabel@...gutronix.de,
        mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: hantro: fix compatible string deprecation warning

On 2022-05-17 15:35, Martin Kepplinger wrote:
> of_device_is_compatible() in the end uses strlen of the string
> for comparison, so in this case, the condition is true even if
> the requested string "nxp,imx8mq-vpu-g1" is being used. The first
> chars containing "nxp,imx8mq-vpu" are the same.

Have you seen this go wrong in practice? AFAICS, unless you're on SPARC, 
which seems somewhat unlikely for an i.MX8 peripheral, of_compat_cmp() 
should map to strcasecmp(), which should do the right thing :/

Robin.

> Fix this by encoding what the comment says.
> 
> Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
> ---
> 
> This is more of a bugreport as the solution doesn't look very elegant
> to me. I'm happy for advice.
> 
> thanks,
>                             martin
> 
> 
>   drivers/staging/media/hantro/hantro_drv.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/media/hantro/hantro_drv.c b/drivers/staging/media/hantro/hantro_drv.c
> index ac232b5f7825..014fab637df0 100644
> --- a/drivers/staging/media/hantro/hantro_drv.c
> +++ b/drivers/staging/media/hantro/hantro_drv.c
> @@ -923,10 +923,11 @@ static int hantro_probe(struct platform_device *pdev)
>   
>   	/*
>   	 * Support for nxp,imx8mq-vpu is kept for backwards compatibility
> -	 * but it's deprecated. Please update your DTS file to use
> -	 * nxp,imx8mq-vpu-g1 or nxp,imx8mq-vpu-g2 instead.
> +	 * but it's deprecated.
>   	 */
> -	if (of_device_is_compatible(pdev->dev.of_node, "nxp,imx8mq-vpu"))
> +	if ((of_device_is_compatible(pdev->dev.of_node, "nxp,imx8mq-vpu")) &&
> +	    (!of_device_is_compatible(pdev->dev.of_node, "nxp,imx8mq-vpu-g1")) &&
> +	    (!of_device_is_compatible(pdev->dev.of_node, "nxp,imx8mq-vpu-g2")))
>   		dev_warn(&pdev->dev, "%s compatible is deprecated\n",
>   			 match->compatible);
>