Re: [PATCH v4] serial: make uart_console_write->putchar()'s character an unsigned char

From: Neil Armstrong
Date: Thu Mar 03 2022 - 03:12:17 EST

On 03/03/2022 09:08, 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: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Cc: Tobias Klauser <tklauser@xxxxxxxxxx>
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: Florian Fainelli <f.fainelli@xxxxxxxxx>
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>
---
[v2] make it unsigned
[v3] fix also sunsab
[v4] fix also sunplus (added quite recently)

drivers/tty/goldfish.c | 2 +-
drivers/tty/hvc/hvc_dcc.c | 2 +-
drivers/tty/serial/21285.c | 2 +-
drivers/tty/serial/8250/8250_early.c | 2 +-
drivers/tty/serial/8250/8250_ingenic.c | 2 +-
drivers/tty/serial/8250/8250_port.c | 2 +-
drivers/tty/serial/altera_jtaguart.c | 4 ++--
drivers/tty/serial/altera_uart.c | 2 +-
drivers/tty/serial/amba-pl010.c | 2 +-
drivers/tty/serial/amba-pl011.c | 6 +++---
drivers/tty/serial/apbuart.c | 2 +-
drivers/tty/serial/ar933x_uart.c | 2 +-
drivers/tty/serial/arc_uart.c | 2 +-
drivers/tty/serial/atmel_serial.c | 2 +-
drivers/tty/serial/bcm63xx_uart.c | 2 +-
drivers/tty/serial/clps711x.c | 2 +-
drivers/tty/serial/digicolor-usart.c | 2 +-
drivers/tty/serial/dz.c | 2 +-
drivers/tty/serial/earlycon-arm-semihost.c | 2 +-
drivers/tty/serial/earlycon-riscv-sbi.c | 2 +-
drivers/tty/serial/fsl_linflexuart.c | 4 ++--
drivers/tty/serial/fsl_lpuart.c | 4 ++--
drivers/tty/serial/imx.c | 2 +-
drivers/tty/serial/imx_earlycon.c | 2 +-
drivers/tty/serial/ip22zilog.c | 2 +-
drivers/tty/serial/lantiq.c | 2 +-
drivers/tty/serial/liteuart.c | 2 +-
drivers/tty/serial/lpc32xx_hs.c | 2 +-
drivers/tty/serial/meson_uart.c | 2 +-
drivers/tty/serial/milbeaut_usio.c | 2 +-
drivers/tty/serial/mps2-uart.c | 4 ++--
drivers/tty/serial/mvebu-uart.c | 4 ++--
drivers/tty/serial/mxs-auart.c | 2 +-
drivers/tty/serial/omap-serial.c | 4 ++--
drivers/tty/serial/owl-uart.c | 2 +-
drivers/tty/serial/pch_uart.c | 2 +-
drivers/tty/serial/pic32_uart.c | 2 +-
drivers/tty/serial/pmac_zilog.c | 2 +-
drivers/tty/serial/pxa.c | 2 +-
drivers/tty/serial/qcom_geni_serial.c | 2 +-
drivers/tty/serial/rda-uart.c | 2 +-
drivers/tty/serial/sa1100.c | 2 +-
drivers/tty/serial/samsung_tty.c | 4 ++--
drivers/tty/serial/sb1250-duart.c | 2 +-
drivers/tty/serial/sccnxp.c | 2 +-
drivers/tty/serial/serial_core.c | 2 +-
drivers/tty/serial/serial_txx9.c | 2 +-
drivers/tty/serial/sh-sci.c | 2 +-
drivers/tty/serial/sifive.c | 4 ++--
drivers/tty/serial/sprd_serial.c | 4 ++--
drivers/tty/serial/st-asc.c | 2 +-
drivers/tty/serial/stm32-usart.c | 2 +-
drivers/tty/serial/sunplus-uart.c | 5 +++--
drivers/tty/serial/sunsab.c | 2 +-
drivers/tty/serial/sunsu.c | 2 +-
drivers/tty/serial/sunzilog.c | 4 ++--
drivers/tty/serial/uartlite.c | 4 ++--
drivers/tty/serial/vr41xx_siu.c | 2 +-
drivers/tty/serial/vt8500_serial.c | 2 +-
drivers/tty/serial/xilinx_uartps.c | 2 +-
drivers/tty/serial/zs.c | 2 +-
include/linux/serial_core.h | 2 +-
62 files changed, 77 insertions(+), 76 deletions(-)


[...]

--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -516,7 +516,7 @@ static void meson_uart_enable_tx_engine(struct uart_port *port)
writel(val, port->membase + AML_UART_CONTROL);
}
-static void meson_console_putchar(struct uart_port *port, int ch)
+static void meson_console_putchar(struct uart_port *port, unsigned char ch)
{
if (!port->membase)
return;

[...]
Acked-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx> # meson_serial