On Wed, May 13, 2020 at 1:34 AM Saravana Kannan <[email protected]> wrote: > > 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.
I took a look at is_visible(). It only makes sense for a group of attributes that are exposed in a sub directory. But state_synced is a top level property IMO. What I'm doing is similar to the "online" attribute that's exposed for a device. And even if I create a group with one lone attribute, I'll still have to add it after the device has probed or have to call sysfs_update_groups() after the device is probed to update the visibility. Seems quite messy and unnecessarily complicated. I'd like to keep this an attribute and not create a group for that reason. Does that sound okay to you? I'll obviously still do the clean up correctly. -Saravana
