Re: Serial Driver Name Question (kernels 2.4.x)

Andrew Morton
2002-01-03T04:45:32Z

Ivan Passos wrote:
>
> (Please CC your answer to me, as I'm not a subscriber of this list.)
>
> Hello,
>
> By looking at tty_io.c:_tty_make_name(), it seems that the TTY
> subsystem in the Linux 2.4.x kernel series expects driver.name to be
> in the form "ttyX%d", even if you're not using devfs. I say that
> because as of now the definition in serial.c for this variable is:
>
> #if defined(CONFIG_DEVFS_FS)
> serial_driver.name = "tts/%d";
> #else
> serial_driver.name = "ttyS";
> #endif
>
> , when it seems it should be:
>
> #if defined(CONFIG_DEVFS_FS)
> serial_driver.name = "tts/%d";
> #else
> serial_driver.name = "ttyS%d";
> #endif
>

I don't think so. Some quick grepping indicates that _all_
tty drivers currently use the "ttyS" equivalent if !CONFIG_DEVFS.

Instead, it appears that someone broke tty_name(). Here's the
2.2 kernel's version:

char *tty_name(struct tty_struct *tty, char *buf)
{
if (tty)
sprintf(buf, "%s%d", tty->driver.name, TTY_NUMBER(tty));
else
strcpy(buf, "NULL tty");
return buf;
}

And that's much more sensible. The tty has a name associated with
what it is (eg "ttyS") - correlates with major number, probably.
And it has an instance number.

Which is cleaner, IMO, than embedding printf control strings
in the driver name.

--- linux-2.4.18-pre1/drivers/char/tty_io.c Wed Dec 26 11:47:40 2001
+++ linux-akpm/drivers/char/tty_io.c Wed Jan 2 20:39:53 2002
@@ -194,7 +194,7 @@ _tty_make_name(struct tty_struct *tty, c
if (!tty) /* Hmm. NULL pointer. That's fun. */
strcpy(buf, "NULL tty");
else
- sprintf(buf, name,
+ sprintf(buf, "%s%d", name,
idx + tty->driver.name_base);

return buf;

Does this look (and work) OK to you?

-