linux-kernel - Re: [PATCH -next] usb: host: drop pointless static qualifier

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Date:   Wed, 23 Jan 2019 11:09:30 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     YueHaibing <yuehaibing@...wei.com>
cc:     geoff@...radead.org, <gregkh@...uxfoundation.org>,
        <benh@...nel.crashing.org>, <paulus@...ba.org>,
        <mpe@...erman.id.au>, <linux-kernel@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH -next] usb: host: drop pointless static qualifier

On Wed, 23 Jan 2019, YueHaibing wrote:

> There is no need to have the 'dummy_mask' variable static since new
> value always be assigned before use it.
> 
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  drivers/usb/host/ehci-ps3.c | 2 +-
>  drivers/usb/host/ohci-ps3.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/host/ehci-ps3.c b/drivers/usb/host/ehci-ps3.c
> index 454d8c6..91cee02 100644
> --- a/drivers/usb/host/ehci-ps3.c
> +++ b/drivers/usb/host/ehci-ps3.c
> @@ -86,7 +86,7 @@ static int ps3_ehci_probe(struct ps3_system_bus_device *dev)
>  	int result;
>  	struct usb_hcd *hcd;
>  	unsigned int virq;
> -	static u64 dummy_mask;
> +	u64 dummy_mask;
>  
>  	if (usb_disabled()) {
>  		result = -ENODEV;
> diff --git a/drivers/usb/host/ohci-ps3.c b/drivers/usb/host/ohci-ps3.c
> index 395f9d3..a1c1bdf 100644
> --- a/drivers/usb/host/ohci-ps3.c
> +++ b/drivers/usb/host/ohci-ps3.c
> @@ -69,7 +69,7 @@ static int ps3_ohci_probe(struct ps3_system_bus_device *dev)
>  	int result;
>  	struct usb_hcd *hcd;
>  	unsigned int virq;
> -	static u64 dummy_mask;
> +	u64 dummy_mask;
>  
>  	if (usb_disabled()) {
>  		result = -ENODEV;

No.  You need to read the code and understand how a variable is used
before you decide to modify it.

In this case, a suitable approach would be to change the declaration 
so that it says:

	status u64 dummy_mask = DMA_BIT_MASK(32);

and remove the line that does the assignment dynamically.

Alan Stern