Re: [systemd-devel] [PATCHv2] tty: Set correct tty name in 'active' sysfs attribute
On Thu, Feb 6, 2014 at 5:29 PM, Greg Kroah-Hartman gre...@linuxfoundation.org wrote: On Thu, Feb 06, 2014 at 04:44:20PM +0100, Hannes Reinecke wrote: On 02/06/2014 04:29 PM, Greg Kroah-Hartman wrote: On Thu, Feb 06, 2014 at 03:27:43PM +0100, Hannes Reinecke wrote: The 'active' sysfs attribute should refer to the currently active tty devices the console is running on, not the currently active console. That's not what Documentation/ABI/sysfs-tty says: Shows the list of currently configured console devices, like 'tty1 ttyS0'. The last entry in the file is the active device connected to /dev/console. The file supports poll() to detect virtual console switches. The problem is indeed with 'console devices'. There is no such thing; you only have tty devices where the console is running on. The console structure doesn't refer to any device in sysfs, only the tty the console is running on has. That sentance doesn't make sense. So we need to print out the tty names in 'active', not the console names. But that doesn't match the documentation. What exactly are you trying to fix here? What is the problem that the current file has that is broken? And as you are changing what this file means, what will break if the information in the file changes? systemd is using the 'active' sysfs attribute to figure out on which _tty_ device to start a getty on. As soon as the console name and the tty name are different you have no means of figuring out which _device_ to open. AFAICS the console 'device' (ie the current entry in 'active') doesn't have _any_ equivalent in sysfs; it just so happens that for most console drivers the tty driver name is identical. But this is not a requirement, and fails for drivers which have a different device for the console and the tty. EG on S/390 the 3270 tty has the devices /dev/3270/tty1 but the console driver announces the name 'tty3270'. So as per current rules the 'active' attribute contains tty32700 which correct as per documentation, but doesn't have _any_ equivalent in sysfs. Martin has the grubby details here. But of course, the documentation should be updated to match the new behavior. Ok, care to send an updated version, that fixes the Documentation as well? If Kay agrees that this is the correct solution, I'll be glad to take it. Sounds good to me. The intention clearly was to point to the device in use, which we can find then. I would not expect problems with this change. For common uses it is the same name already and nothing visibly should change, and for the ones where it isn't the same, I expect it is not too useful to find the driver name. Thanks, Kay ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] [PATCHv2] tty: Set correct tty name in 'active' sysfs attribute
On 02/06/2014 04:29 PM, Greg Kroah-Hartman wrote: On Thu, Feb 06, 2014 at 03:27:43PM +0100, Hannes Reinecke wrote: The 'active' sysfs attribute should refer to the currently active tty devices the console is running on, not the currently active console. That's not what Documentation/ABI/sysfs-tty says: Shows the list of currently configured console devices, like 'tty1 ttyS0'. The last entry in the file is the active device connected to /dev/console. The file supports poll() to detect virtual console switches. The problem is indeed with 'console devices'. There is no such thing; you only have tty devices where the console is running on. The console structure doesn't refer to any device in sysfs, only the tty the console is running on has. That sentance doesn't make sense. So we need to print out the tty names in 'active', not the console names. But that doesn't match the documentation. What exactly are you trying to fix here? What is the problem that the current file has that is broken? And as you are changing what this file means, what will break if the information in the file changes? systemd is using the 'active' sysfs attribute to figure out on which _tty_ device to start a getty on. As soon as the console name and the tty name are different you have no means of figuring out which _device_ to open. AFAICS the console 'device' (ie the current entry in 'active') doesn't have _any_ equivalent in sysfs; it just so happens that for most console drivers the tty driver name is identical. But this is not a requirement, and fails for drivers which have a different device for the console and the tty. EG on S/390 the 3270 tty has the devices /dev/3270/tty1 but the console driver announces the name 'tty3270'. So as per current rules the 'active' attribute contains tty32700 which correct as per documentation, but doesn't have _any_ equivalent in sysfs. Martin has the grubby details here. But of course, the documentation should be updated to match the new behavior. Cheers, Hannes -- Dr. Hannes Reinecke zSeries Storage h...@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] [PATCHv2] tty: Set correct tty name in 'active' sysfs attribute
On Thu, Feb 06, 2014 at 04:44:20PM +0100, Hannes Reinecke wrote: On 02/06/2014 04:29 PM, Greg Kroah-Hartman wrote: On Thu, Feb 06, 2014 at 03:27:43PM +0100, Hannes Reinecke wrote: The 'active' sysfs attribute should refer to the currently active tty devices the console is running on, not the currently active console. That's not what Documentation/ABI/sysfs-tty says: Shows the list of currently configured console devices, like 'tty1 ttyS0'. The last entry in the file is the active device connected to /dev/console. The file supports poll() to detect virtual console switches. The problem is indeed with 'console devices'. There is no such thing; you only have tty devices where the console is running on. The console structure doesn't refer to any device in sysfs, only the tty the console is running on has. That sentance doesn't make sense. So we need to print out the tty names in 'active', not the console names. But that doesn't match the documentation. What exactly are you trying to fix here? What is the problem that the current file has that is broken? And as you are changing what this file means, what will break if the information in the file changes? systemd is using the 'active' sysfs attribute to figure out on which _tty_ device to start a getty on. As soon as the console name and the tty name are different you have no means of figuring out which _device_ to open. AFAICS the console 'device' (ie the current entry in 'active') doesn't have _any_ equivalent in sysfs; it just so happens that for most console drivers the tty driver name is identical. But this is not a requirement, and fails for drivers which have a different device for the console and the tty. EG on S/390 the 3270 tty has the devices /dev/3270/tty1 but the console driver announces the name 'tty3270'. So as per current rules the 'active' attribute contains tty32700 which correct as per documentation, but doesn't have _any_ equivalent in sysfs. Martin has the grubby details here. But of course, the documentation should be updated to match the new behavior. Ok, care to send an updated version, that fixes the Documentation as well? If Kay agrees that this is the correct solution, I'll be glad to take it. thanks, greg k-h ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
