[PATCH] TTY: export NR_LDISC and N_* line discipline numbers to user-space

[PATCH] TTY: export NR_LDISC and N_* line discipline numbers to user-space

[Florian Fainelli]

From: Florian Fainelli <ffainelli@freebox.fr>

Since commit (4564f9e5: consolidate line discipline number definitions)
the patch moved all line discipline number from a per-architecture termios.h
to a shared one: tty.h. However, prior to this consolidation work, the
line discipline numbers were outside of an ifdef __KERNEL__/endif block
so these numbers used to be exported to user-space.

Since such numbers are kernel ABI anyway, and tty.h is already included
for user- space header processing, just move these relevant defines
outside of the ifdef __KERNEL__/endif block in include/linux/tty.h.

CC: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Florian Fainelli <ffainelli@freebox.fr>
---
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 9f469c7..272dc9a 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -5,24 +5,6 @@
  * 'tty.h' defines some structures used by tty_io.c and some defines.
  */
 
-#ifdef __KERNEL__
-#include <linux/fs.h>
-#include <linux/major.h>
-#include <linux/termios.h>
-#include <linux/workqueue.h>
-#include <linux/tty_driver.h>
-#include <linux/tty_ldisc.h>
-#include <linux/mutex.h>
-
-#include <asm/system.h>
-
-
-/*
- * (Note: the *_driver.minor_start values 1, 64, 128, 192 are
- * hardcoded at present.)
- */
-#define NR_UNIX98_PTY_DEFAULT	4096      /* Default maximum for Unix98 ptys */
-#define NR_UNIX98_PTY_MAX	(1 << MINORBITS) /* Absolute limit */
 #define NR_LDISCS		30
 
 /* line disciplines */
@@ -51,6 +33,25 @@
 #define N_GSM0710	21	/* GSM 0710 Mux */
 #define N_TI_WL		22	/* for TI's WL BT, FM, GPS combo chips */
 
+#ifdef __KERNEL__
+#include <linux/fs.h>
+#include <linux/major.h>
+#include <linux/termios.h>
+#include <linux/workqueue.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_ldisc.h>
+#include <linux/mutex.h>
+
+#include <asm/system.h>
+
+
+/*
+ * (Note: the *_driver.minor_start values 1, 64, 128, 192 are
+ * hardcoded at present.)
+ */
+#define NR_UNIX98_PTY_DEFAULT	4096      /* Default maximum for Unix98 ptys */
+#define NR_UNIX98_PTY_MAX	(1 << MINORBITS) /* Absolute limit */
+
 /*
  * This character is the same as _POSIX_VDISABLE: it cannot be used as
  * a c_cc[] character, but indicates that a particular special character
-- 
1.7.4.1

Re: [PATCH] TTY: export NR_LDISC and N_* line discipline numbers to user-space

[Greg KH]

On Tue, May 24, 2011 at 10:43:03AM +0200, Florian Fainelli wrote:
> From: Florian Fainelli <ffainelli@freebox.fr>
> 
> Since commit (4564f9e5: consolidate line discipline number definitions)
> the patch moved all line discipline number from a per-architecture termios.h
> to a shared one: tty.h. However, prior to this consolidation work, the
> line discipline numbers were outside of an ifdef __KERNEL__/endif block
> so these numbers used to be exported to user-space.
> 
> Since such numbers are kernel ABI anyway, and tty.h is already included
> for user- space header processing, just move these relevant defines
> outside of the ifdef __KERNEL__/endif block in include/linux/tty.h.

Any reason you didn't copy _any_ of the people who signed off on that
patch, or the original author of that patch?

Anyway, this is been this way for four years, since the 2.6.21 kernel
release.  Since no one has noticed, or complained, since then, how much
a problem is this really?

Meaning, why has it taken this long for anyone to notice?

thanks,

greg k-h

Re: [PATCH] TTY: export NR_LDISC and N_* line discipline numbers to user-space

[Florian Fainelli]

Hello,

On Tuesday 24 May 2011 14:40:44 Greg KH wrote:
> On Tue, May 24, 2011 at 10:43:03AM +0200, Florian Fainelli wrote:
> > From: Florian Fainelli <ffainelli@freebox.fr>
> > 
> > Since commit (4564f9e5: consolidate line discipline number definitions)
> > the patch moved all line discipline number from a per-architecture
> > termios.h to a shared one: tty.h. However, prior to this consolidation
> > work, the line discipline numbers were outside of an ifdef
> > __KERNEL__/endif block so these numbers used to be exported to
> > user-space.
> > 
> > Since such numbers are kernel ABI anyway, and tty.h is already included
> > for user- space header processing, just move these relevant defines
> > outside of the ifdef __KERNEL__/endif block in include/linux/tty.h.
> 
> Any reason you didn't copy _any_ of the people who signed off on that
> patch, or the original author of that patch?

No particular reason but my mistake, fixed that.

> 
> Anyway, this is been this way for four years, since the 2.6.21 kernel
> release.  Since no one has noticed, or complained, since then, how much
> a problem is this really?

This is a problem because you may have out of tree drivers using a line 
discpline number, and you do not want your companion user-space application to 
have to use a different line discpline number but the one the kernel should 
provide.

> 
> Meaning, why has it taken this long for anyone to notice?

- long standing user-space applications such as pppd got their N_PPP long ago, 
and do not have to worry about N_PPP being renumbered so they can just define 
it in pppd's sources it won't break

- I started implementing a line discipline driver only a couple of months ago 
and then realized that such ABI should have been exported
--
Florian

Re: [PATCH] TTY: export NR_LDISC and N_* line discipline numbers to user-space

[Greg KH]

On Tue, May 24, 2011 at 03:17:23PM +0200, Florian Fainelli wrote:
> Hello,
> 
> On Tuesday 24 May 2011 14:40:44 Greg KH wrote:
> > On Tue, May 24, 2011 at 10:43:03AM +0200, Florian Fainelli wrote:
> > > From: Florian Fainelli <ffainelli@freebox.fr>
> > > 
> > > Since commit (4564f9e5: consolidate line discipline number definitions)
> > > the patch moved all line discipline number from a per-architecture
> > > termios.h to a shared one: tty.h. However, prior to this consolidation
> > > work, the line discipline numbers were outside of an ifdef
> > > __KERNEL__/endif block so these numbers used to be exported to
> > > user-space.
> > > 
> > > Since such numbers are kernel ABI anyway, and tty.h is already included
> > > for user- space header processing, just move these relevant defines
> > > outside of the ifdef __KERNEL__/endif block in include/linux/tty.h.
> > 
> > Any reason you didn't copy _any_ of the people who signed off on that
> > patch, or the original author of that patch?
> 
> No particular reason but my mistake, fixed that.
> 
> > 
> > Anyway, this is been this way for four years, since the 2.6.21 kernel
> > release.  Since no one has noticed, or complained, since then, how much
> > a problem is this really?
> 
> This is a problem because you may have out of tree drivers using a line 
> discpline number, and you do not want your companion user-space application to 
> have to use a different line discpline number but the one the kernel should 
> provide.
> 
> > 
> > Meaning, why has it taken this long for anyone to notice?
> 
> - long standing user-space applications such as pppd got their N_PPP long ago, 
> and do not have to worry about N_PPP being renumbered so they can just define 
> it in pppd's sources it won't break
> 
> - I started implementing a line discipline driver only a couple of months ago 
> and then realized that such ABI should have been exported

Ok, then it really isn't that important of a change :)

I'll queue it up for the next major merge window after this one, thanks.

greg k-h

Re: [PATCH] TTY: export NR_LDISC and N_* line discipline numbers to user-space

[Florian Fainelli]

On Tuesday 24 May 2011 15:33:53 Greg KH wrote:
> On Tue, May 24, 2011 at 03:17:23PM +0200, Florian Fainelli wrote:
> > Hello,
> > 
> > On Tuesday 24 May 2011 14:40:44 Greg KH wrote:
> > > On Tue, May 24, 2011 at 10:43:03AM +0200, Florian Fainelli wrote:
> > > > From: Florian Fainelli <ffainelli@freebox.fr>
> > > > 
> > > > Since commit (4564f9e5: consolidate line discipline number
> > > > definitions) the patch moved all line discipline number from a
> > > > per-architecture termios.h to a shared one: tty.h. However, prior to
> > > > this consolidation work, the line discipline numbers were outside of
> > > > an ifdef
> > > > __KERNEL__/endif block so these numbers used to be exported to
> > > > user-space.
> > > > 
> > > > Since such numbers are kernel ABI anyway, and tty.h is already
> > > > included for user- space header processing, just move these relevant
> > > > defines outside of the ifdef __KERNEL__/endif block in
> > > > include/linux/tty.h.
> > > 
> > > Any reason you didn't copy _any_ of the people who signed off on that
> > > patch, or the original author of that patch?
> > 
> > No particular reason but my mistake, fixed that.
> > 
> > > Anyway, this is been this way for four years, since the 2.6.21 kernel
> > > release.  Since no one has noticed, or complained, since then, how much
> > > a problem is this really?
> > 
> > This is a problem because you may have out of tree drivers using a line
> > discpline number, and you do not want your companion user-space
> > application to have to use a different line discpline number but the one
> > the kernel should provide.
> > 
> > > Meaning, why has it taken this long for anyone to notice?
> > 
> > - long standing user-space applications such as pppd got their N_PPP long
> > ago, and do not have to worry about N_PPP being renumbered so they can
> > just define it in pppd's sources it won't break
> > 
> > - I started implementing a line discipline driver only a couple of months
> > ago and then realized that such ABI should have been exported
> 
> Ok, then it really isn't that important of a change :)
> 
> I'll queue it up for the next major merge window after this one, thanks.

Thanks!
--
Florian

Re: [PATCH] TTY: export NR_LDISC and N_* line discipline numbers to user-space

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 1699 bytes --]

Am 24.05.2011 15:17 schrieb Florian Fainelli:
> On Tuesday 24 May 2011 14:40:44 Greg KH wrote:
>> On Tue, May 24, 2011 at 10:43:03AM +0200, Florian Fainelli wrote:
>>> From: Florian Fainelli <ffainelli@freebox.fr>
>>>
>>> Since commit (4564f9e5: consolidate line discipline number definitions)
>>> the patch moved all line discipline number from a per-architecture
>>> termios.h to a shared one: tty.h. However, prior to this consolidation
>>> work, the line discipline numbers were outside of an ifdef
>>> __KERNEL__/endif block so these numbers used to be exported to
>>> user-space.
>>>
>>> Since such numbers are kernel ABI anyway, and tty.h is already included
>>> for user- space header processing, just move these relevant defines
>>> outside of the ifdef __KERNEL__/endif block in include/linux/tty.h.
[...]
>> Meaning, why has it taken this long for anyone to notice?
> 
> - long standing user-space applications such as pppd got their N_PPP long ago, 
> and do not have to worry about N_PPP being renumbered so they can just define 
> it in pppd's sources it won't break

Also, I just checked on openSUSE 11.2, which comes with kernel
release is 2.6.27, and it still defines the LD numbers in
/usr/include/bits/ioctl-types.h (included from sys/ioctl.h).
I guess other distributions are doing the same, so their users
wouldn't notice the change.

Anyway, the patch is fine by me. Feel free to add:

Acked-by: Tilman Schmidt <tilman@imap.cc>

Thanks,
Tilman

-- 
Tilman Schmidt                    E-Mail: tilman@imap.cc
Bonn, Germany
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