Messages in this thread | | | From | Dmitry Torokhov <> | Date | Sat, 6 Jul 2019 10:39:38 -0700 | Subject | Re: [PATCH 01/12 v2] Platform: add a dev_groups pointer to struct platform_driver |
| |
On Sat, Jul 6, 2019 at 10:19 AM Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > > On Sat, Jul 06, 2019 at 10:04:39AM -0700, Dmitry Torokhov wrote: > > Hi Greg, > > > > On Sat, Jul 6, 2019 at 1:32 AM Greg Kroah-Hartman > > <gregkh@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 > > > > <gregkh@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. > > Sorry, I didn't mean to imply that only platform drivers want to do > this, as you say, many other drivers do as well. > > > 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. > > Yeah, I know, we need to add this type of functionality to those busses > as well. I don't see a way of doing it other than this bus-by-bus > conversion, do you?
Can't you push the **dev_groups from platform driver down to the generic driver structure and handle them in driver_sysfs_add()?
> > > > > 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. > > I agree, but again, this is a kobject change (adding attributes), so > I think the event type I picked here is the correct one.
I guess once you push it all into core you'll end up with 2 uevents being emitted back-to-back and this seems inefficient.
If you really want KOBJ_CHANGE maybe have some additional attribute like "CHANGE=driver-specific-attrs" in it? It's all quite ugly though.
Thanks.
-- Dmitry
| |