On Wed, May 13, 2020 at 1:22 AM Greg Kroah-Hartman <[email protected]> wrote: > > On Tue, May 12, 2020 at 06:34:15PM -0700, Saravana Kannan wrote: > > This can be used to check if a device supports sync_state() callbacks > > and therefore keeps resources left on by the bootloader enabled till all > > its consumers have probed. > > > > This can also be used to check if sync_state() has been called for a > > device or whether it is still trying to keep resources enabled because > > they were left enabled by the bootloader and all its consumers haven't > > probed yet. > > > > Signed-off-by: Saravana Kannan <[email protected]> > > --- > > .../ABI/testing/sysfs-devices-state_synced | 24 +++++++++++++++++++ > > drivers/base/dd.c | 16 +++++++++++++ > > 2 files changed, 40 insertions(+) > > create mode 100644 Documentation/ABI/testing/sysfs-devices-state_synced > > > > diff --git a/Documentation/ABI/testing/sysfs-devices-state_synced > > b/Documentation/ABI/testing/sysfs-devices-state_synced > > new file mode 100644 > > index 000000000000..0c922d7d02fc > > --- /dev/null > > +++ b/Documentation/ABI/testing/sysfs-devices-state_synced > > @@ -0,0 +1,24 @@ > > +What: /sys/devices/.../state_synced > > +Date: May 2020 > > +Contact: Saravana Kannan <[email protected]> > > +Description: > > + The /sys/devices/.../state_synced attribute is only present > > for > > + devices whose bus types or driver provides the .sync_state() > > + callback. The number read from it (0 or 1) reflects the value > > + of the device's 'state_synced' field. A value of 0 means the > > + .sync_state() callback hasn't been called yet. A value of 1 > > + means the .sync_state() callback has been called. > > + > > + Generally, if a device has sync_state() support and has some > > of > > + the resources it provides enabled at the time the kernel > > starts > > + (Eg: enabled by hardware reset or bootloader or anything that > > + run before the kernel starts), then it'll keep those resources > > + enabled and in a state that's compatible with the state they > > + were in at the start of the kernel. The device will stop doing > > + this only when the sync_state() callback has been called -- > > + which happens only when all its consumer devices are > > registered > > + and have probed successfully. Resources that were left > > disabled > > + at the time the kernel starts are not affected or limited in > > + any way by sync_state() callbacks. > > + > > + > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > index 48ca81cb8ebc..72599436ae84 100644 > > --- a/drivers/base/dd.c > > +++ b/drivers/base/dd.c > > @@ -458,6 +458,13 @@ static void driver_deferred_probe_add_trigger(struct > > device *dev, > > driver_deferred_probe_trigger(); > > } > > > > +static ssize_t state_synced_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + return sprintf(buf, "%u\n", dev->state_synced); > > +} > > +static DEVICE_ATTR_RO(state_synced); > > + > > static int really_probe(struct device *dev, struct device_driver *drv) > > { > > int ret = -EPROBE_DEFER; > > @@ -531,9 +538,16 @@ static int really_probe(struct device *dev, struct > > device_driver *drv) > > goto dev_groups_failed; > > } > > > > + if (dev_has_sync_state(dev) && > > + device_create_file(dev, &dev_attr_state_synced)) { > > + dev_err(dev, "state_synced sysfs add failed\n"); > > + goto dev_sysfs_state_synced_failed; > > + } > > Why not add this to the groups above this and only enable it if needed > at runtime?
Those groups above seem to be driver specific groups. Looking at the code, some drivers seem to be setting them. Also, this attribute can only be decided after a driver has successfully bound to the device because dev_has_sync_state() has to check the bus and the driver for sync_state() support. > The is_visible() callback should be what you need to use here. If this is an attribute specific property, it might work. I'll take a look. > That > will save you lots of housekeeping as well as properly remove the > attribute when the device is removed from the system (which you didn't > explicitly do in this patch...) I had a nagging feeling I was missing something. Duh! I'll make sure I do proper clean up in v2. Thanks for the review. -Saravana
