Re: [PATCH 1/3] serial: Add Goldfish TTY driver

[Yao Zi <me@ziyao.cc>]

On Sun, Dec 21, 2025 at 12:28:49AM +0800, Kuan-Wei Chiu wrote:
> Hi Yao,
> 
> On Fri, Dec 19, 2025 at 03:14:03AM +0000, Yao Zi wrote:
> > On Thu, Dec 18, 2025 at 06:52:50PM +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 <visitorckw@gmail.com>
> > > ---
> > >  MAINTAINERS                      |   6 ++
> > >  drivers/serial/Kconfig           |   8 +++
> > >  drivers/serial/Makefile          |   1 +
> > >  drivers/serial/serial_goldfish.c | 112 +++++++++++++++++++++++++++++++
> > >  include/goldfish_tty.h           |  18 +++++
> > >  5 files changed, 145 insertions(+)
> > >  create mode 100644 drivers/serial/serial_goldfish.c
> > >  create mode 100644 include/goldfish_tty.h

...

> For reference, here is the planned update for v2:
> 
> 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));
> 	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;
> }

Thanks for the explanation, this version looks fine to me.

> Regards,
> Kuan-Wei

Regards,
Yao Zi

> > > +}
> > 
> > Best regards,
> > Yao Zi
> > 
> > [1]: https://lore.kernel.org/u-boot/20251212142859.GQ303283@bill-the-cat