Hi Yao, On Sat, Dec 27, 2025 at 02:07:47AM +0000, Yao Zi wrote: > On Fri, Dec 26, 2025 at 05:53:57PM +0000, Kuan-Wei Chiu wrote: > > Add support for the Google Goldfish TTY serial device. This virtual > > device is commonly used in QEMU virtual machines (such as the m68k > > virt machine) and Android emulators. > > > > The driver implements basic console output and input polling using the > > Goldfish MMIO interface. > > > > Signed-off-by: Kuan-Wei Chiu <[email protected]> > > --- > > Changes in v2: > > - Update SPDX license identifier to GPL-2.0-or-later. > > - Sort header inclusions alphabetically. > > - Move RX buffer into goldfish_tty_priv instead of using a static buffer. > > - Make sure getc only read a single byte at a time. > > > > MAINTAINERS | 6 ++ > > drivers/serial/Kconfig | 8 +++ > > drivers/serial/Makefile | 1 + > > drivers/serial/serial_goldfish.c | 104 +++++++++++++++++++++++++++++++ > > include/goldfish_tty.h | 18 ++++++ > > 5 files changed, 137 insertions(+) > > create mode 100644 drivers/serial/serial_goldfish.c > > create mode 100644 include/goldfish_tty.h > > ... > > > diff --git a/drivers/serial/serial_goldfish.c > > b/drivers/serial/serial_goldfish.c > > new file mode 100644 > > index 00000000000..ce5bff6bf4c > > --- /dev/null > > +++ b/drivers/serial/serial_goldfish.c > > @@ -0,0 +1,104 @@ > > +// SPDX-License-Identifier: GPL-2.0-or-later > > +/* > > + * Copyright (C) 2025, Kuan-Wei Chiu <[email protected]> > > + * Goldfish TTY driver for U-Boot > > + */ > > + > > +#include <asm/io.h> > > +#include <dm.h> > > +#include <goldfish_tty.h> > > +#include <linux/types.h> > > +#include <serial.h> > > + > > +/* Goldfish TTY Register Offsets */ > > +#define GOLDFISH_TTY_PUT_CHAR 0x00 > > +#define GOLDFISH_TTY_BYTES_READY 0x04 > > +#define GOLDFISH_TTY_CMD 0x08 > > +#define GOLDFISH_TTY_DATA_PTR 0x10 > > +#define GOLDFISH_TTY_DATA_LEN 0x14 > > +#define GOLDFISH_TTY_DATA_PTR_HIGH 0x18 > > +#define GOLDFISH_TTY_VERSION 0x20 > > + > > +/* Commands */ > > +#define CMD_WRITE_BUFFER 2 > > +#define CMD_READ_BUFFER 3 > > + > > +struct goldfish_tty_priv { > > + void __iomem *base; > > + u8 rx_buf; > > +}; > > + > > +static int goldfish_serial_getc(struct udevice *dev) > > +{ > > + struct goldfish_tty_priv *priv = dev_get_priv(dev); > > + unsigned long base = (unsigned long)priv->base; > > + unsigned long paddr; > > + u32 count; > > + > > + count = __raw_readl((void *)(base + GOLDFISH_TTY_BYTES_READY)); > > I think it's okay to do pointer arithmetic directly against priv->base > in GNU C, right? In which case void * is treated like char *. > > If I'm correct, variable base could be dropped, and we could avoid some > casts here and below.
Agreed. While standard C doesn't allow it, GNU C does support arithmetic on void *. Doing this directly makes the code look much cleaner. Thanks for the feedback, I will update this in v3. Regards, Kuan-Wei > > > + if (count == 0) > > + return -EAGAIN; > > + > > + paddr = virt_to_phys((void *)&priv->rx_buf); > > + > > + __raw_writel(0, (void *)(base + GOLDFISH_TTY_DATA_PTR_HIGH)); > > + __raw_writel(paddr, (void *)(base + GOLDFISH_TTY_DATA_PTR)); > > + __raw_writel(1, (void *)(base + GOLDFISH_TTY_DATA_LEN)); > > + > > + __raw_writel(CMD_READ_BUFFER, (void *)(base + GOLDFISH_TTY_CMD)); > > + > > + return priv->rx_buf; > > +} > > Regards, > Yao Zi
