On Wed, 2013-11-20 at 18:32 -0600, Scott Wood wrote: > For userspace value setting, it looks like gpiolib blocks the write if > the pin if FLAG_IS_OUT is set. This suggests that this is an error > condition for other uses as well. Though, I notice that > mpc8xxx_gpio_dir_out() calls gpio_set() before actually changing the > direction. So it may be useful to avoid races where the wrong value is > output briefly after the direction is changed (especially in open drain > situations, where the signal could have a meaningful default even before > we begin outputting). But that raises the question of how you'd do that > from userspace, and it also renders the to-be-output value as write-only > data (until the direction is actually changed), since a readback would > get the input value instead. > > > So maybe it's better to eliminate the effects of the ->data to the > > input pins when reading the status, regardless of the possible changes > > of the pins and the data. > > Do you think so? > > Perhaps, but that doesn't require you to modify ->data in the get() > function. > > -Scott > I think you considered about this more comprehensive. I'll update the code without the modification of ->data in the get() function, and also with the comments from Anatolij.
Best Regards, Liu Gang _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev