linux-kernel - Re: [PATCH v3] serial: make uart_console_write->putchar()'s character an unsigned char

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Message-ID: <20220302175242.ejiaf36vszr4xvou@pengutronix.de>
Date:   Wed, 2 Mar 2022 18:52:42 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     gregkh@...uxfoundation.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
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Subject: Re: [PATCH v3] serial: make uart_console_write->putchar()'s
 character an unsigned char

On Wed, Mar 02, 2022 at 08:27:32AM +0100, Jiri Slaby wrote:
> Currently, uart_console_write->putchar's second parameter (the
> character) is of type int. It makes little sense, provided uart_console_write()
> accepts the input string as "const char *s" and passes its content -- the
> characters -- to putchar(). So switch the character's type to unsigned
> char.
> 
> We don't use char as that is signed on some platforms. That would cause
> troubles for drivers which (implicitly) cast the char to u16 when
> writing to the device. Sign extension would happen in that case and the
> value written would be completely different to the provided char. DZ is
> an example of such a driver -- on MIPS, it uses u16 for dz_out in
> dz_console_putchar().

I always thought this was bigger than 8bit for hardware that supports
wider characters. But if that's the case that's completely unsupported,
there isn't even CS9.

So

Acked-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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