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

[Vladimir Zapolskiy]

On 3/2/22 9:27 AM, 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.
>
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> Acked-by: Richard Genoud <richard.genoud@xxxxxxxxx> [atmel_serial]
> Acked-by: Florian Fainelli <f.fainelli@xxxxxxxxx> [bcm63xx_uart]
> Acked-by: Tobias Klauser <tklauser@xxxxxxxxxx> [altera_*]
> Cc: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxx>
> Cc: Vineet Gupta <vgupta@xxxxxxxxxx>
> Cc: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
> Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
> Cc: Ludovic Desroches <ludovic.desroches@xxxxxxxxxxxxx>
> Cc: bcm-kernel-feedback-list@xxxxxxxxxxxx
> Cc: Alexander Shiyan <shc_work@xxxxxxx>
> Cc: Baruch Siach <baruch@xxxxxxxxxx>
> Cc: "Maciej W. Rozycki" <macro@xxxxxxxxxxx>
> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
> Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
> Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> Cc: Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx>
> Cc: Fabio Estevam <festevam@xxxxxxxxx>
> Cc: NXP Linux Team <linux-imx@xxxxxxx>
> Cc: Karol Gugala <kgugala@xxxxxxxxxxxx>
> Cc: Mateusz Holenko <mholenko@xxxxxxxxxxxx>
> Cc: Vladimir Zapolskiy <vz@xxxxxxxxx>
> Cc: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Cc: Kevin Hilman <khilman@xxxxxxxxxxxx>
> Cc: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
> Cc: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> Cc: Taichi Sugaya <sugaya.taichi@xxxxxxxxxxxxx>
> Cc: Takao Orito <orito.takao@xxxxxxxxxxxxx>
> Cc: Liviu Dudau <liviu.dudau@xxxxxxx>
> Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: "Andreas Färber" <afaerber@xxxxxxx>
> Cc: Manivannan Sadhasivam <mani@xxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: Andy Gross <agross@xxxxxxxxxx>
> Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxx>
> Cc: Orson Zhai <orsonzhai@xxxxxxxxx>
> Cc: Baolin Wang <baolin.wang7@xxxxxxxxx>
> Cc: Chunyan Zhang <zhang.lyra@xxxxxxxxx>
> Cc: Patrice Chotard <patrice.chotard@xxxxxxxxxxx>
> Cc: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>
> Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Peter Korsgaard <peter@xxxxxxxxxxxxx>
> Cc: Michal Simek <michal.simek@xxxxxxxxxx>
> ---

[snip]

> diff --git a/drivers/tty/serial/lpc32xx_hs.c b/drivers/tty/serial/lpc32xx_hs.c
> index 54437a087aa0..93140cac1ca1 100644
> --- a/drivers/tty/serial/lpc32xx_hs.c
> +++ b/drivers/tty/serial/lpc32xx_hs.c
> @@ -122,7 +122,7 @@ static void wait_for_xmit_ready(struct uart_port *port)
>   	}
>   }
>   
> -static void lpc32xx_hsuart_console_putchar(struct uart_port *port, int ch)
> +static void lpc32xx_hsuart_console_putchar(struct uart_port *port, unsigned char ch)
>   {
>   	wait_for_xmit_ready(port);
>   	writel((u32)ch, LPC32XX_HSUART_FIFO(port->membase));

for NXP LPC32xx HS UART:

Acked-by: Vladimir Zapolskiy <vz@xxxxxxxxx>

--
Best wishes,
Vladimir