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SubjectRe: [PATCH] console_print: change the function api to make it have printk style interface
On Tue, 25 Aug 2009 16:47:49 -0700 Anirban Sinha wrote:

> Hi Folks:
>
> I bumped into this function in printk.c a while back. As I started using
> it, I wondered if we could enhance it with printk style interface that
> could make it somewhat more useful.
>
> One straightforward thing to do here would perhaps be to define this as
> a macro. Something like this:
>
> #define console_print(fmt,msg...) printk(KERN_EMERG fmt,##msg)
>
> However, there might be some important reason why this was not done. I
> do not know.
> Anyway, keeping the existing code of using a proper C function and
> exporting the symbol, here's a patch that enhances the function to use
> prink style interface. To the best of my knowledge, I do not think it
> will break existing code that uses this function. I did a grep through
> the kernel code and didn't look like this call was used in lot of other
> places. I have also built the kernel locally with this change and looks
> like at least for mips, it does not break our build.
>
> CCing Linus for his opinion.
>
> Cheers,
>
> Ani
>
>
> Signed-off-by: Anirban Sinha <asinha@zeugmasystems.com>
> ---
> drivers/char/serial167.c | 2 +-
> include/linux/tty.h | 2 +-
> kernel/printk.c | 14 ++++++++++++--
> 3 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/serial167.c b/drivers/char/serial167.c
> index 51e7a46..029aa0d 100644
> --- a/drivers/char/serial167.c
> +++ b/drivers/char/serial167.c
> @@ -171,7 +171,7 @@ static int startup(struct cyclades_port *);
> static void cy_throttle(struct tty_struct *);
> static void cy_unthrottle(struct tty_struct *);
> static void config_setup(struct cyclades_port *);
> -extern void console_print(const char *);
> +extern int console_print(const char *, ...);

Drop that. Add
#include <linux/tty.h>
if it's not already #included.


> #ifdef CYCLOM_SHOW_STATUS
> static void show_status(int);
> #endif
> diff --git a/include/linux/tty.h b/include/linux/tty.h
> index e8c6c91..eb3e4fe 100644
> --- a/include/linux/tty.h
> +++ b/include/linux/tty.h
> @@ -519,7 +519,7 @@ extern int pcxe_open(struct tty_struct *tty, struct
> file *filp);
>
> /* printk.c */
>
> -extern void console_print(const char *);
> +extern int console_print(const char *, ...);

Make that prototype be like printk, with the __attribute__ ((format (printf, 1, 2))):


int printk(const char * fmt, ...)
__attribute__ ((format (printf, 1, 2)));


>
> /* vt.c */
>
> diff --git a/kernel/printk.c b/kernel/printk.c
> index b4d97b5..729b0ff 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -1060,9 +1060,19 @@ void __sched console_conditional_schedule(void)
> }
> EXPORT_SYMBOL(console_conditional_schedule);
>
> -void console_print(const char *s)
> +int console_print(const char *fmt, ...)
> {
> - printk(KERN_EMERG "%s", s);
> + va_list args;
> + int r;
> + char _fmt[1024] = KERN_EMERG;
> +
> + strncat(_fmt, fmt,sizeof(_fmt)- sizeof(KERN_EMERG));
> +
> + va_start(args, fmt);
> + r = vprintk(_fmt, args);
> + va_end(args);
> +
> + return r;
> }
> EXPORT_SYMBOL(console_print);
>
> --


---
~Randy
LPC 2009, Sept. 23-25, Portland, Oregon
http://linuxplumbersconf.org/2009/


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