On Fri, Mar 5, 2021 at 9:55 AM Greg KH <gre...@linuxfoundation.org> wrote: > > On Fri, Mar 05, 2021 at 09:45:41AM +0100, Bartosz Golaszewski wrote: > > On Fri, Mar 5, 2021 at 9:34 AM Greg KH <gre...@linuxfoundation.org> wrote: > > > > > > On Fri, Mar 05, 2021 at 09:18:30AM +0100, Geert Uytterhoeven wrote: > > > > CC Greg > > > > > > > > On Thu, Mar 4, 2021 at 11:30 AM Bartosz Golaszewski <b...@bgdev.pl> > > > > wrote: > > > > > > > > > > From: Bartosz Golaszewski <bgolaszew...@baylibre.com> > > > > > > > > > > Export the symbol for device_is_bound() so that we can use it in > > > > > gpio-sim > > > > > to check if the simulated GPIO chip is bound before fetching its > > > > > driver > > > > > data from configfs callbacks in order to retrieve the name of the GPIO > > > > > chip device. > > > > > > > > > > Signed-off-by: Bartosz Golaszewski <bgolaszew...@baylibre.com> > > > > > --- > > > > > drivers/base/dd.c | 1 + > > > > > 1 file changed, 1 insertion(+) > > > > > > > > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > > > > index 9179825ff646..c62c02e3490a 100644 > > > > > --- a/drivers/base/dd.c > > > > > +++ b/drivers/base/dd.c > > > > > @@ -353,6 +353,7 @@ bool device_is_bound(struct device *dev) > > > > > { > > > > > return dev->p && klist_node_attached(&dev->p->knode_driver); > > > > > } > > > > > +EXPORT_SYMBOL_GPL(device_is_bound); > > > > > > No. Please no. Why is this needed? Feels like someone is doing > > > something really wrong... > > > > > > NACK. > > > > > > > I should have Cc'ed you the entire series, my bad. > > > > This is the patch that uses this change - it's a new, improved testing > > module for GPIO using configfs & sysfs as you (I think) suggested a > > while ago: > > > > https://lkml.org/lkml/2021/3/4/355 > > > > The story goes like this: committing the configfs item registers a > > platform device. > > Ick, no, stop there, that's not a "real" device, please do not abuse > platform devices like that, you all know I hate this :( > > Use the virtbus code instead perhaps? >
I have no idea what virtbus is and grepping for it only returns three hits in: ./drivers/pci/iov.c and it's a function argument. If it stands for virtual bus then for sure it sounds like the right thing but I need to find more info on this. > > As far as I understand - there's no guarantee that > > the device will be bound to a driver before the commit callback (or > > more specifically platform_device_register_full() in this case) > > returns so the user may try to retrieve the name of the device > > immediately (normally user-space should wait for the associated uevent > > but nobody can force that) by doing: > > > > mv /sys/kernel/config/gpio-sim/pending/foo /sys/kernel/config/gpio-sim/live/ > > cat /sys/kernel/config/gpio-sim/live/foo/dev_name > > > > If the device is not bound at this point, we'll have a crash in the > > kernel as opposed to just returning -ENODEV. > > How will the kernel crash? What has created the dev_name sysfs file > before it is possible to be read from? That feels like the root > problem. > It's not sysfs - it's in configfs. Each chip has a read-only configfs attribute that returns the name of the device - I don't really have a better idea to map the configfs items to devices that committing creates. > > Please advise on how to handle it without device_is_bound(). > > Please do not create sysfs files before they can be read from :) > Don't worry, I don't. Bartosz