linux-kernel - Re: [PATCH 03/21] ata: libahci_platform: Explicitly set rc on devres

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Message-ID: <19912886-4032-633e-e4a7-ef47ae389ffd@opensource.wdc.com>
Date:   Tue, 29 Mar 2022 17:20:18 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Rob Herring <robh+dt@...nel.org>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 03/21] ata: libahci_platform: Explicitly set rc on
 devres_alloc failure

On 3/24/22 09:16, Serge Semin wrote:
> It's better for readability and maintainability to explicitly assign an
> error number to the variable used then as a return value from the method
> on the cleanup-on-error path. So adding new code in the method we won't
> have to think whether the overridden rc-variable is set afterward in case
> of an error. Saving one line of code doesn't worth it especially seeing
> the rest of the ahci_platform_get_resources() function errors handling
> blocks do explicitly write errno to rc.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> ---
>  drivers/ata/libahci_platform.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
> index 18296443ccba..1bd2f1686239 100644
> --- a/drivers/ata/libahci_platform.c
> +++ b/drivers/ata/libahci_platform.c
> @@ -389,7 +389,7 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>  	struct ahci_host_priv *hpriv;
>  	struct clk *clk;
>  	struct device_node *child;
> -	int i, enabled_ports = 0, rc = -ENOMEM, child_nodes;
> +	int i, enabled_ports = 0, rc = 0, child_nodes;

You I did say that I do not like this. Especially considering that this
function uses rc only in the case of an error return. Having it uselessly
initialized to 0 does not make sense and goes against your goal of
avoiding problems in case it is not set in an error path. returning
"ERR_PTR(0)" is the same as returning NULL, which defeats the purpose of
using ERR_PTR/PTR_ERR.

Please drop this patch.

>  	u32 mask_port_map = 0;
>  
>  	if (!devres_open_group(dev, NULL, GFP_KERNEL))
> @@ -397,8 +397,10 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>  
>  	hpriv = devres_alloc(ahci_platform_put_resources, sizeof(*hpriv),
>  			     GFP_KERNEL);
> -	if (!hpriv)
> +	if (!hpriv) {
> +		rc = -ENOMEM;
>  		goto err_out;
> +	}
>  
>  	devres_add(dev, hpriv);
>  


-- 
Damien Le Moal
Western Digital Research