On Sun, Mar 17, 2013 at 3:20 PM, Myron Stowe <mstowe@xxxxxxxxxx> wrote: > On Sun, 2013-03-17 at 15:00 +0100, Kay Sievers wrote: >> On Sun, Mar 17, 2013 at 2:38 PM, Alex Williamson >> <alex.williamson@xxxxxxxxxx> wrote: >> > I'm assuming that the device only breaks because udevadm is dumping the >> > full I/O port register space of the device and that if an actual driver >> > was interacting with it through this interface that it would work. Who >> > knows how many devices will have read side-effects by udevadm blindly >> > dumping these files. Thanks, >> >> Sysfs is a too public interface to export things there which make >> devices/driver choke on a simple read() of an attribute. >> >> This is nothing specific to udevadm, any tool can do that. Udevadm >> will never read any of the files during normal operation. The admin >> explicitly asked udevadm with a specific command to dump all the stuff >> the device offers. >> >> The kernel driver needs to be fixed to allow that, in the worst case, >> the attributes not exported at all. People should take more care what >> they export in /sys, it's not a hidden and private ioctl what's >> exported there, stuff is very visible and will be looked at. >> >> Telling userspace not to use specific stuff in /sys I would not expect >> to work as a strategy; there is too much weird stuff out there that >> will always try to do that ... > > Kay - could you comment on Foot Note 3 in > https://lkml.org/lkml/2013/3/16/168 > > With respect to 'udev', you are working on the assumption that all files > in sysfs must be readable with no consequences which may be implied by > the Documentation's sysfs.txt file's mentioning ASCII. If we are to > interpret that as strictly as you seem to want to then why is there > sysfs support for creating binary files? They cannot be distinguished from outside, so there is nothing I know that could make a difference to userspace tools. Tools -- no matter how useful they are not not, it's that they do that for many years already -- need to be able to read() the stuff in there, without causing any damage to the system. Kay -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
