linux-kernel - Re: [PATCH 16/36] sh: dma-sysfs: move to use bus_get_dev

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Date:   Mon, 13 Mar 2023 19:48:44 +0100
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     rafael@...nel.org, Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org
Subject: Re: [PATCH 16/36] sh: dma-sysfs: move to use bus_get_dev_root()

Hi Greg!

On Mon, 2023-03-13 at 19:28 +0100, Greg Kroah-Hartman wrote:
> Direct access to the struct bus_type dev_root pointer is going away soon
> so replace that with a call to bus_get_dev_root() instead, which is what
> it is there for.
> 
> Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> Cc: Rich Felker <dalias@...c.org>
> Cc: linux-sh@...r.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
> Note, this is a patch that is a prepatory cleanup as part of a larger
> series of patches that is working on resolving some old driver core
> design mistakes.  It will build and apply cleanly on top of 6.3-rc2 on
> its own, but I'd prefer if I could take it through my driver-core tree
> so that the driver core changes can be taken through there for 6.4-rc1.
> 
>  arch/sh/drivers/dma/dma-sysfs.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/sh/drivers/dma/dma-sysfs.c b/arch/sh/drivers/dma/dma-sysfs.c
> index 8ef318150f84..431bc18f0a41 100644
> --- a/arch/sh/drivers/dma/dma-sysfs.c
> +++ b/arch/sh/drivers/dma/dma-sysfs.c
> @@ -45,13 +45,19 @@ static DEVICE_ATTR(devices, S_IRUGO, dma_show_devices, NULL);
>  
>  static int __init dma_subsys_init(void)
>  {
> +	struct device *dev_root;
>  	int ret;
>  
>  	ret = subsys_system_register(&dma_subsys, NULL);
>  	if (unlikely(ret))
>  		return ret;
>  
> -	return device_create_file(dma_subsys.dev_root, &dev_attr_devices);
> +	dev_root = bus_get_dev_root(&dma_subsys);
> +	if (dev_root) {
> +		ret = device_create_file(dev_root, &dev_attr_devices);
> +		put_device(dev_root);
> +	}
> +	return ret;
>  }
>  postcore_initcall(dma_subsys_init);
>  

After acking this, I noticed that if bus_get_dev_root() fails, "ret" remains
set to the value by subsys_system_register() which might confuse the caller
thinking that dma_subsys_init() succeeded unless I am missing something?

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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