linux-kernel - RE: [PATCH v4 16/18] staging: r8188eu: hal: Clean up rtw_read*() and rtw

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Date:   Tue, 14 Sep 2021 14:33:24 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'Fabio M. De Francesco'" <fmdefrancesco@...il.com>,
        Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Straube <straube.linux@...il.com>
CC:     Pavel Skripkin <paskripkin@...il.com>
Subject: RE: [PATCH v4 16/18] staging: r8188eu: hal: Clean up rtw_read*() and
 rtw_write*()

From: Fabio M. De Francesco
> Sent: 13 September 2021 19:10
...
> +	u16 address = (u16)(addr & 0xffff);
> 
> -	usbctrl_vendorreq(pintfhdl, wvalue, &data, 1, REALTEK_USB_VENQT_READ);
> +	usbctrl_vendorreq(intfhdl, address, &data, 1, REALTEK_USB_VENQT_READ);

You really don't need the (u16) cast or the '& 0xffff'.
The assignment will just truncate.

But do you even need to truncate the value at all?
It rather depends on what happens inside usbctrl_vendorreq()
and whether the parameter to this code is already constrained.

I think modern gcc are better, but I have seen code where
the '& 0xffff' masked the value, then the (u16) masked the
value and finally the low 16 bits were written into a structure.

(Oh the other patches are now readable - a lot of junk down the pan.)

	David

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