linux-kernel - RE: [PATCH 0/4] serial: 8250: Fixes for Oxford Semiconductor 950 UARTs

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Message-ID: <aff02581e694421eba04afc2fc3644df@AcuMS.aculab.com>
Date:   Tue, 15 Jun 2021 21:45:31 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'Maciej W. Rozycki'" <macro@...am.me.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Jiri Slaby <jirislaby@...nel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 0/4] serial: 8250: Fixes for Oxford Semiconductor 950
 UARTs

From: Maciej W. Rozycki
> Sent: 15 June 2021 18:13
...
>  As I have noted above there is a data type signedness difference between
> `mcr_mask' and UART_MCR_CLKSEL.  So we have the value of 0x80 (128).
> Once bitwise-complemented it becomes 0xffffff7f (-129).  Once assigned to
> `mcr_mask' however it becomes 0x7f (127), which is considered an unsafe
> conversion between signed and unsigned integers by GCC, which is why the
> compiler complains about it.

Blame the iso C standards committee for making integer promotions
'value preserving' instead of 'sign preserving' as they were in K&R C.

Try using ^ 0xffu instead of ~.

	David

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