Re: [PATCH] tty: serial: samsung: support driver modulization

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Dec 05, 2019 at 04:36:48PM +0100, Krzysztof Kozlowski wrote:
> On Sun, 1 Dec 2019 at 09:05, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Sun, Dec 01, 2019 at 04:59:14PM +0900, Hyunki Koo wrote:
> > > From: Shinbeom Choi <sbeom.choi@samsung.com>
> > >
> > > This commit enables modulization of samsung uart driver.
> > >
> > > There was no way to make use of this driver in other module,
> > > because uart functions were static.
> > >
> > > By exporting required functions, user can use this driver
> > > in other module.
> > >
> > > Signed-off-by: Shinbeom Choi <sbeom.choi@samsung.com>
> > > Signed-off-by: Hyunki Koo <hyunki00.koo@samsung.com>
> > > ---
> > >  drivers/tty/serial/samsung.h     | 32 ++++++++++++
> > >  drivers/tty/serial/samsung_tty.c | 85 +++++++++++++++-----------------
> > >  2 files changed, 73 insertions(+), 44 deletions(-)
> > >
> > > diff --git a/drivers/tty/serial/samsung.h b/drivers/tty/serial/samsung.h
> > > index f93022113f59..25be0962284d 100644
> > > --- a/drivers/tty/serial/samsung.h
> > > +++ b/drivers/tty/serial/samsung.h
> > > @@ -144,4 +144,36 @@ static inline void s3c24xx_clear_bit(struct uart_port *port, int idx,
> > >       local_irq_restore(flags);
> > >  }
> > >
> > > +#if defined(CONFIG_ARCH_EXYNOS)
> > > +#define EXYNOS_COMMON_SERIAL_DRV_DATA                                \
> > > +     .info = &(struct s3c24xx_uart_info) {                   \
> > > +             .name           = "Samsung Exynos UART",        \
> > > +             .type           = PORT_S3C6400,                 \
> > > +             .has_divslot    = 1,                            \
> > > +             .rx_fifomask    = S5PV210_UFSTAT_RXMASK,        \
> > > +             .rx_fifoshift   = S5PV210_UFSTAT_RXSHIFT,       \
> > > +             .rx_fifofull    = S5PV210_UFSTAT_RXFULL,        \
> > > +             .tx_fifofull    = S5PV210_UFSTAT_TXFULL,        \
> > > +             .tx_fifomask    = S5PV210_UFSTAT_TXMASK,        \
> > > +             .tx_fifoshift   = S5PV210_UFSTAT_TXSHIFT,       \
> > > +             .def_clk_sel    = S3C2410_UCON_CLKSEL0,         \
> > > +             .num_clks       = 1,                            \
> > > +             .clksel_mask    = 0,                            \
> > > +             .clksel_shift   = 0,                            \
> > > +     },                                                      \
> > > +     .def_cfg = &(struct s3c2410_uartcfg) {                  \
> > > +             .ucon           = S5PV210_UCON_DEFAULT,         \
> > > +             .ufcon          = S5PV210_UFCON_DEFAULT,        \
> > > +             .has_fracval    = 1,                            \
> > > +     }                                                       \
> > > +
> > > +#endif
> > > +
> > > +int s3c24xx_serial_get_ports(struct s3c24xx_uart_port **ourport, int index);
> > > +int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
> > > +                                 struct platform_device *platdev);
> > > +int s3c24xx_serial_unregister_port(struct platform_device *dev);
> > > +int s3c24xx_serial_suspend(struct device *dev);
> > > +int s3c24xx_serial_resume(struct device *dev);
> > > +int s3c24xx_serial_resume_noirq(struct device *dev);
> > >  #endif
> > > diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> > > index 83fd51607741..15414ecd9008 100644
> > > --- a/drivers/tty/serial/samsung_tty.c
> > > +++ b/drivers/tty/serial/samsung_tty.c
> > > @@ -1735,7 +1735,7 @@ static int s3c24xx_serial_enable_baudclk(struct s3c24xx_uart_port *ourport)
> > >   * initialise a single serial port from the platform device given
> > >   */
> > >
> > > -static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
> > > +int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
> > >                                   struct platform_device *platdev)
> > >  {
> > >       struct uart_port *port = &ourport->port;
> > > @@ -1842,12 +1842,24 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
> > >       /* reset the fifos (and setup the uart) */
> > >       s3c24xx_serial_resetport(port, cfg);
> > >
> > > +     if (!s3c24xx_uart_drv.state) {
> > > +             ret = uart_register_driver(&s3c24xx_uart_drv);
> > > +             if (ret < 0) {
> > > +                     dev_err(port->dev, "Failed to register Samsung UART driver\n");
> > > +                     return ret;
> > > +             }
> > > +     }
> > > +
> > > +     dbg("%s: adding port\n", __func__);
> > > +     uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
> > > +
> > >       return 0;
> > >
> > >  err:
> > >       port->mapbase = 0;
> > >       return ret;
> > >  }
> > > +EXPORT_SYMBOL_GPL(s3c24xx_serial_init_port);
> >
> > Why are you exporting all of these functions?  What other code uses
> > them?  Why are you converting them all to global functions I don't see
> > any other in-kernel callers, so why are those changes needed here?
> >
> > totally confused,
> 
> I cannot find the original email from Hyunki on mailing lists (neither
> LKML nor serial) so this was not even public till Greg replied.

I think it might have been sent in html format.

> Anyway, probably this is for new Android and some out-of-tree usage...
> but it is wrong.

Making the driver be able to be built as a module is a good thing, no
matter what project is causing the work to have happen.

And yes, it's Android :)

thanks,

greg k-h