Hi Greg, On Sat, Jul 6, 2019 at 1:32 AM Greg Kroah-Hartman <gre...@linuxfoundation.org> wrote: > > On Thu, Jul 04, 2019 at 02:17:22PM -0700, Dmitry Torokhov wrote: > > Hi Greg, > > > > On Thu, Jul 4, 2019 at 5:15 AM Greg Kroah-Hartman > > <gre...@linuxfoundation.org> wrote: > > > > > > Platform drivers like to add sysfs groups to their device, but right now > > > they have to do it "by hand". The driver core should handle this for > > > them, but there is no way to get to the bus-default attribute groups as > > > all platform devices are "special and unique" one-off drivers/devices. > > > > > > To combat this, add a dev_groups pointer to platform_driver which allows > > > a platform driver to set up a list of default attributes that will be > > > properly created and removed by the platform driver core when a probe() > > > function is successful and removed right before the device is unbound. > > > > Why is this limited to platform bus? Drivers for other buses also > > often want to augment list of their attributes during probe(). I'd > > move it to generic probe handling. > > This is not limited to the platform at all, the driver core supports > this for any bus type today, but it's then up to the bus-specific code > to pass that on to the driver core. That's usually set for the > bus-specific attributes that they want exposed for all devices of that > bus type (see the bus_groups, dev_groups, and drv_groups pointers in > struct bus_type). > > For the platform devices, the problem is that this is something that the > individual drivers want after they bind to the device. And as all > platform devices are "different" they can't be a "common" set of > attributes, so they need to be created after the device is bound to the > driver.
I believe that your assertion that only platform devices want to install custom attributes is incorrect. Drivers for devices attached to serio, i2c, USB, spi, etc, etc, all have additional attributes: dtor@dtor-ws:~/kernel/work (master *)$ grep -l '\(i2c\|usb\|spi\)' `git grep -l '\(device_add_group\|sysfs_create_group\)' -- drivers` | wc -l 170 I am pretty sure some of this count is false positives, but majority is actually proper hits. ... > > > > We already emit KOBJ_BIND when we finish binding device to a driver, > > regardless of the bus. I know we still need to teach systemd to handle > > it properly, but I think it is better than sprinkling KOBJ_CHANGE > > around. > > But the object's attributes did just change, which is what KOBJ_CHANGE > tells userspace, so this should be the correct thing to say to > userspace. > > And yes, ideally KOBJ_BIND would be handled, and it will be sent once > the device's probe function succeeds, but we have to deal with old > userspaces as well, right? Not for the new functionality, I do not think so. Newer kernels should be compatible with older userspace as it not breaking it, but new functionality is not guaranteed to be available with older userspace. Thanks. -- Dmitry
