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Date:   Thu, 3 Mar 2022 07:32:59 +0100
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Subject: Re: [PATCH v3] serial: make uart_console_write->putchar()'s character
 an unsigned char
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To:     gregkh@linuxfoundation.org
Cc:     linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
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References: <20220302072732.1916-1-jslaby@suse.cz>
From:   Jiri Slaby <jslaby@suse.cz>
In-Reply-To: <20220302072732.1916-1-jslaby@suse.cz>
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On 02. 03. 22, 8:27, 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().
> 
> Note we do the char -> uchar conversion implicitly in
> uart_console_write(). Provided we do not change size of the data type,
> sign extension does not happen there, so the problem is void.
> 
> This makes the types consistent and unified with the rest of the uart
> layer, which uses unsigned char in most places already. One exception is
> xmit_buf, but that is going to be converted later.

Kbuild seems to serve me this one by one. So this patch is still incomplete:
 > drivers/tty/serial/sunplus-uart.c:526:7: error: incompatible function 
pointer types passing 'void (struct uart_port *, int)' to parameter of 
type 'void (*)(struct uart_port *, unsigned char)'

regards,
-- 
js
suse labs