[PATCH] serial/8250: Increase number of serial ports to 32

[PATCH] serial/8250: Increase number of serial ports to 32

[Yegor Yefremov]

This will make sure that multiple serial port cards can be
used out of the box. Otherwise the user must pass
nr_uarts parameter, that will be often forgotten and increases
support requests for serial card vendors.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

Index: b/drivers/serial/Kconfig
===================================================================
--- a/drivers/serial/Kconfig	2010-11-10 03:53:21.000000000 +0100
+++ b/drivers/serial/Kconfig	2010-11-10 14:32:54.000000000 +0100
@@ -119,7 +119,7 @@
 config SERIAL_8250_NR_UARTS
 	int "Maximum number of 8250/16550 serial ports"
 	depends on SERIAL_8250
-	default "4"
+	default "32"
 	help
 	  Set this to the number of serial ports you want the driver
 	  to support.  This includes any ports discovered via ACPI or
@@ -130,7 +130,7 @@
 	int "Number of 8250/16550 serial ports to register at runtime"
 	depends on SERIAL_8250
 	range 0 SERIAL_8250_NR_UARTS
-	default "4"
+	default "32"
 	help
 	  Set this to the maximum number of serial ports you want
 	  the kernel to register at boot time.  This can be overridden

Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Greg KH]

On Wed, Nov 10, 2010 at 02:54:39PM +0100, Yegor Yefremov wrote:
> This will make sure that multiple serial port cards can be
> used out of the box. Otherwise the user must pass
> nr_uarts parameter, that will be often forgotten and increases
> support requests for serial card vendors.

Has this really happened in the past?  What is the downside of changing
this option that has been around for many years now?  Also note that
multi-port serial cards are more rare these days than they used to be so
changing this seems a bit pointless now.

thanks,

greg k-h

Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Yegor Yefremov]

Am 10.11.2010 17:08, schrieb Greg KH:
> On Wed, Nov 10, 2010 at 02:54:39PM +0100, Yegor Yefremov wrote:
>> This will make sure that multiple serial port cards can be
>> used out of the box. Otherwise the user must pass
>> nr_uarts parameter, that will be often forgotten and increases
>> support requests for serial card vendors.
> Has this really happened in the past?

It is still the case. The most requests that we get are "the card doesn't function under Ubuntu...". After examining dmesg one could see that 8250 driver is initialized with 4 UARTS.

There are also lots of questions and bugs concerning this subject. Like this one: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/125524. I even found some entries from 2010:
http://www.gnulinux.in/forum/4-port-serial-card-installation-fedora-11

> What is the downside of changing
> this option that has been around for many years now?  Also note that
> multi-port serial cards are more rare these days than they used to be so
> changing this seems a bit pointless now.

I can say that those cards are still selling. They're not dead.

The downside is that those card are not working out of the box and users not experienced in Linux often miss this parameter. Also some Live Linuxes like Ubuntu (perhaps I missed something) don't provide command line parameter, so you have to reload the driver with proper parameter.

I understand that it is somehow a responsibility of distribution maintainers to properly configure the kernel, but I hope that if vanilla kernel would increase default value, then they will also follow.

Best regards,
Yegor

Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Greg KH]

On Wed, Nov 10, 2010 at 06:02:39PM +0100, Yegor Yefremov wrote:
> Am 10.11.2010 17:08, schrieb Greg KH:
> > On Wed, Nov 10, 2010 at 02:54:39PM +0100, Yegor Yefremov wrote:
> >> This will make sure that multiple serial port cards can be
> >> used out of the box. Otherwise the user must pass
> >> nr_uarts parameter, that will be often forgotten and increases
> >> support requests for serial card vendors.
> > Has this really happened in the past?
> 
> It is still the case. The most requests that we get are "the card
> doesn't function under Ubuntu...". After examining dmesg one could see
> that 8250 driver is initialized with 4 UARTS.
> 
> There are also lots of questions and bugs concerning this subject.
> Like this one:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/125524. I even
> found some entries from 2010:
> http://www.gnulinux.in/forum/4-port-serial-card-installation-fedora-11

Then get the distro to change the default setting of their kernels.

> > What is the downside of changing
> > this option that has been around for many years now?  Also note that
> > multi-port serial cards are more rare these days than they used to be so
> > changing this seems a bit pointless now.
> 
> I can say that those cards are still selling. They're not dead.
> 
> The downside is that those card are not working out of the box and
> users not experienced in Linux often miss this parameter. Also some
> Live Linuxes like Ubuntu (perhaps I missed something) don't provide
> command line parameter, so you have to reload the driver with proper
> parameter.
> 
> I understand that it is somehow a responsibility of distribution
> maintainers to properly configure the kernel, but I hope that if
> vanilla kernel would increase default value, then they will also
> follow.

I doubt it as they would never notice that the value changed at all
(they run 'make oldconfig').  So please just work with the distros that
you are having problems with to get the value changed.

thanks,

greg k-h

Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Matt Schulte]

On Wed, Nov 10, 2010 at 10:08 AM, Greg KH <greg@kroah.com> wrote:
> On Wed, Nov 10, 2010 at 02:54:39PM +0100, Yegor Yefremov wrote:
>> This will make sure that multiple serial port cards can be
>> used out of the box. Otherwise the user must pass
>> nr_uarts parameter, that will be often forgotten and increases
>> support requests for serial card vendors.
>
> Has this really happened in the past?  What is the downside of changing
> this option that has been around for many years now?  Also note that
> multi-port serial cards are more rare these days than they used to be so
> changing this seems a bit pointless now.
>

Multiport serial cards are not dead, we still sell bunches.  This is
one of those problems that really frustrates our customers.  They want
their ports to show up by default and the only way to do it is to
recompile the kernel or modify the boot line.  A lot of my customers
don't like the 82510.nr_uarts work around in grub and so we have to
hold their hands while they figure out how to recompile the kernel
with support for more ports.  I think the default number of ports
should definitely be changed from 4 to at least 8, maybe even 16 or
32.

Matt Schulte
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Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Greg KH]

On Wed, Nov 10, 2010 at 01:10:51PM -0600, Matt Schulte wrote:
> On Wed, Nov 10, 2010 at 10:08 AM, Greg KH <greg@kroah.com> wrote:
> > On Wed, Nov 10, 2010 at 02:54:39PM +0100, Yegor Yefremov wrote:
> >> This will make sure that multiple serial port cards can be
> >> used out of the box. Otherwise the user must pass
> >> nr_uarts parameter, that will be often forgotten and increases
> >> support requests for serial card vendors.
> >
> > Has this really happened in the past? ?What is the downside of changing
> > this option that has been around for many years now? ?Also note that
> > multi-port serial cards are more rare these days than they used to be so
> > changing this seems a bit pointless now.
> >
> 
> Multiport serial cards are not dead, we still sell bunches.  This is
> one of those problems that really frustrates our customers.  They want
> their ports to show up by default and the only way to do it is to
> recompile the kernel or modify the boot line.  A lot of my customers
> don't like the 82510.nr_uarts work around in grub and so we have to
> hold their hands while they figure out how to recompile the kernel
> with support for more ports.  I think the default number of ports
> should definitely be changed from 4 to at least 8, maybe even 16 or
> 32.

Why not work with the distros to get it changed?  If we change the
default within the kernel, it's still not going to change what they are
using at all, so you will still be having the same problem you are
today.

thanks,

greg k-h

Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Matt Schulte]

On Wed, Nov 10, 2010 at 1:28 PM, Greg KH <greg@kroah.com> wrote:
> On Wed, Nov 10, 2010 at 01:10:51PM -0600, Matt Schulte wrote:
>> On Wed, Nov 10, 2010 at 10:08 AM, Greg KH <greg@kroah.com> wrote:
>> > On Wed, Nov 10, 2010 at 02:54:39PM +0100, Yegor Yefremov wrote:
>> >> This will make sure that multiple serial port cards can be
>> >> used out of the box. Otherwise the user must pass
>> >> nr_uarts parameter, that will be often forgotten and increases
>> >> support requests for serial card vendors.
>> >
>> > Has this really happened in the past? ?What is the downside of changing
>> > this option that has been around for many years now? ?Also note that
>> > multi-port serial cards are more rare these days than they used to be so
>> > changing this seems a bit pointless now.
>> >
>>
>> Multiport serial cards are not dead, we still sell bunches.  This is
>> one of those problems that really frustrates our customers.  They want
>> their ports to show up by default and the only way to do it is to
>> recompile the kernel or modify the boot line.  A lot of my customers
>> don't like the 82510.nr_uarts work around in grub and so we have to
>> hold their hands while they figure out how to recompile the kernel
>> with support for more ports.  I think the default number of ports
>> should definitely be changed from 4 to at least 8, maybe even 16 or
>> 32.
>
> Why not work with the distros to get it changed?  If we change the
> default within the kernel, it's still not going to change what they are
> using at all, so you will still be having the same problem you are
> today.

Don't you think changing it here would eventually propagate down the
chain to all of the distros?  Or do you think they would ignore the
change up here?

Matt Schulte
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Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Greg KH]

On Wed, Nov 10, 2010 at 03:28:24PM -0600, Matt Schulte wrote:
> On Wed, Nov 10, 2010 at 1:28 PM, Greg KH <greg@kroah.com> wrote:
> > On Wed, Nov 10, 2010 at 01:10:51PM -0600, Matt Schulte wrote:
> >> On Wed, Nov 10, 2010 at 10:08 AM, Greg KH <greg@kroah.com> wrote:
> >> > On Wed, Nov 10, 2010 at 02:54:39PM +0100, Yegor Yefremov wrote:
> >> >> This will make sure that multiple serial port cards can be
> >> >> used out of the box. Otherwise the user must pass
> >> >> nr_uarts parameter, that will be often forgotten and increases
> >> >> support requests for serial card vendors.
> >> >
> >> > Has this really happened in the past? ?What is the downside of changing
> >> > this option that has been around for many years now? ?Also note that
> >> > multi-port serial cards are more rare these days than they used to be so
> >> > changing this seems a bit pointless now.
> >> >
> >>
> >> Multiport serial cards are not dead, we still sell bunches. ?This is
> >> one of those problems that really frustrates our customers. ?They want
> >> their ports to show up by default and the only way to do it is to
> >> recompile the kernel or modify the boot line. ?A lot of my customers
> >> don't like the 82510.nr_uarts work around in grub and so we have to
> >> hold their hands while they figure out how to recompile the kernel
> >> with support for more ports. ?I think the default number of ports
> >> should definitely be changed from 4 to at least 8, maybe even 16 or
> >> 32.
> >
> > Why not work with the distros to get it changed? ?If we change the
> > default within the kernel, it's still not going to change what they are
> > using at all, so you will still be having the same problem you are
> > today.
> 
> Don't you think changing it here would eventually propagate down the
> chain to all of the distros?  Or do you think they would ignore the
> change up here?

Speaking as someone who has maintained a distro kernel for a long time
now, it would be totally ignored as it would never show up on their
radar.  Only new options get questioned (i.e. ones that show up when
running 'make oldconfig'), old ones are left alone.

sorry,

greg k-h

Re: [PATCH] serial/8250: Increase number of serial ports to 32

[Yegor Yefremov]

>>>> This will make sure that multiple serial port cards can be
>>>> used out of the box. Otherwise the user must pass
>>>> nr_uarts parameter, that will be often forgotten and increases
>>>> support requests for serial card vendors.
>>> Has this really happened in the past?
>> It is still the case. The most requests that we get are "the card
>> doesn't function under Ubuntu...". After examining dmesg one could see
>> that 8250 driver is initialized with 4 UARTS.
>>
>> There are also lots of questions and bugs concerning this subject.
>> Like this one:
>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/125524. I even
>> found some entries from 2010:
>> http://www.gnulinux.in/forum/4-port-serial-card-installation-fedora-11
> Then get the distro to change the default setting of their kernels.
>
>>> What is the downside of changing
>>> this option that has been around for many years now?  Also note that
>>> multi-port serial cards are more rare these days than they used to be so
>>> changing this seems a bit pointless now.
>> I can say that those cards are still selling. They're not dead.
>>
>> The downside is that those card are not working out of the box and
>> users not experienced in Linux often miss this parameter. Also some
>> Live Linuxes like Ubuntu (perhaps I missed something) don't provide
>> command line parameter, so you have to reload the driver with proper
>> parameter.
>>
>> I understand that it is somehow a responsibility of distribution
>> maintainers to properly configure the kernel, but I hope that if
>> vanilla kernel would increase default value, then they will also
>> follow.
> I doubt it as they would never notice that the value changed at all
> (they run 'make oldconfig').  So please just work with the distros that
> you are having problems with to get the value changed.

I just want to summarize  the effort of increasing the number of run-time UARTs.

openSUSE and Ubuntu both accepted this change without long discussion:
https://bugzilla.novell.com/show_bug.cgi?id=652954
https://bugs.launchpad.net/ubuntu/+bug/675453

ReHat/Fedora rejected the change without really acceptable reason: https://bugzilla.redhat.com/show_bug.cgi?id=657530

By Debian is the question still in discussion: http://lists.debian.org/debian-kernel/2010/11/msg00211.html

Uwe pointed to the discussion about making 8250 UART detection dynamically: http://lists.debian.org/debian-kernel/2010/11/msg00286.html.

Yegor