linux-kernel - Re: [PATCH] usb: core: Remove unnecessary memset()

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Message-ID: <Pine.LNX.4.44L0.1812101503110.1562-100000@iolanthe.rowland.org>
Date:   Mon, 10 Dec 2018 15:06:11 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Suwan Kim <suwan.kim027@...il.com>
cc:     gregkh@...uxfoundation.org, <linux-usb@...r.kernel.org>,
        <mathias.nyman@...ux.intel.com>, <heikki.krogerus@...ux.intel.com>,
        <linux-kernel@...r.kernel.org>, <balbi@...nel.org>
Subject: Re: [PATCH] usb: core: Remove unnecessary memset()

On Tue, 4 Dec 2018, Suwan Kim wrote:

> register_root_hub() calls memset() setting usb_dev->bus->devmap.
> devicemap to 0 during hcd probe function (usb_hcd_pci_probe). But
> in previous function which is also the procedure of usb_hcd_pci_probe(),
> usb_bus_init() already initialized bus->devmap calling memset().
> Furthermore, register_root_hub() is called only once in kernel.
> So, calling memset() which resets usb_bus->devmap.devicemap in
> register_root_hub() is redundant.
> 
> Signed-off-by: Suwan Kim <suwan.kim027@...il.com>
> ---
>  drivers/usb/core/hcd.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 487025d31d44..015b126ce455 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -1074,8 +1074,6 @@ static int register_root_hub(struct usb_hcd *hcd)
>  
>  	usb_dev->devnum = devnum;
>  	usb_dev->bus->devnum_next = devnum + 1;
> -	memset (&usb_dev->bus->devmap.devicemap, 0,
> -			sizeof usb_dev->bus->devmap.devicemap);
>  	set_bit (devnum, usb_dev->bus->devmap.devicemap);
>  	usb_set_device_state(usb_dev, USB_STATE_ADDRESS);

Acked-by: Alan Stern <stern@...land.harvard.edu>