Bug 657530

Summary: serial/8250: Increase number of serial ports detected to 32
Product: [Fedora] Fedora Reporter: Yegor Yefremov <yegorslists>
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED WONTFIX QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: low    
Version: 14CC: dougsland, gansalmon, itamar, jonathan, kernel-maint, kmcmartin, madhu.chinakonda
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OS: Linux   
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Last Closed: 2010-12-09 23:37:11 UTC Type: ---
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Description Yegor Yefremov 2010-11-26 11:09:20 UTC 
Description of problem:

Both CONFIG_SERIAL_8250_NR_UARTS and CONFIG_SERIAL_8250_RUNTIME_UARTS should be
increased to at least 32 in order to support multi port serial cards out of the
box. This will cover at least the situation, where two 8 port cards are used
simultaneously and there is still some room for internal ports or the other
card.

This bug report was created after initial discussion on the linux-serial
mailings list: http://www.spinics.net/lists/linux-serial/msg03020.html

Version-Release number of selected component (if applicable):


How reproducible: 
Always

Steps to Reproduce:
1. insert 8 port serial card based on 8250 UART family
2.
3.
  
Actual results:
only some ports will be detected

Expected results:
all 8 ports must be detected

Additional info:

see already accepted changed in Ubuntu and openSUSE
https://bugzilla.novell.com/show_bug.cgi?id=652954
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/675453
Comment 1 Kyle McMartin 2010-12-09 23:37:11 UTC 
RUNTIME_UARTS will not be increased, as it can be increased with a parameter and isn't necessary for virtually all users.

NR_UARTS is already 32.
Comment 2 Yegor Yefremov 2010-12-10 09:29:28 UTC 
The advantage of such approach is that multiple interface cards can be used at once without user intervention. This would reduce the support effort much, cause this is the most frequent user question: "Why not all ports are detected?". Then we have to point them to this problem and teach them how to make changes in various bootloaders. And this costs time and resources.  

And I don't see any disadvantages in increasing CONFIG_SERIAL_8250_RUNTIME_UARTS. As you already stated NR_UARTS is already 32, so memory is already "wasted". The RUNTIME value cares about registering this amount of ports and if the number of real ports is lower than RUNTIME_UARTS, only those real ports will be installed. So I don't see how it can affect other users.

Have you read this thread (http://www.spinics.net/lists/linux-serial/msg03020.html) completely? After my request to change the default values upstream, Greg Kroah-Hartman made following suggestion:

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

And then the reason:

"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."

If you're still unsure about this lets discuss it on the linux-serial mailingslist.
Comment 3 Kyle McMartin 2010-12-10 14:49:40 UTC 
It's a pointless change for virtually all users. If you don't like it, make the 8250 driver suck less.