Re: [PATCH 01/12 v2] Platform: add a dev_groups pointer to struct platform_driver

[Richard Gong]

Hi Greg,

On 7/25/19 8:44 AM, Greg Kroah-Hartman wrote:
> On Sat, Jul 20, 2019 at 07:38:57AM +0300, Dmitry Torokhov wrote:
> > On Fri, Jul 19, 2019 at 08:52:20PM +0900, Greg Kroah-Hartman wrote:
> > > On Sat, Jul 06, 2019 at 10:39:38AM -0700, Dmitry Torokhov wrote:
> > > > On Sat, Jul 6, 2019 at 10:19 AM Greg Kroah-Hartman
> > > > <gregkh@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> 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()?
> > >
> > > Sorry for the delay, got busy with the merge window...
> > >
> > > Anyway, no, we can't call this then, because driver_sysfs_add() is
> > > called before probe() is called.  So if probe() fails, we don't bind the
> > > device to the driver.  We also should not be creating sysfs files for a
> > > driver that has not had probe() called yet, as internal structures will
> > > not be set up at that time.
> >
> > Ah, yes, I got confused by the fact that driver_sysfs_remove is called
> > early. Anyway, I think you want something like this:
>
> Ah, nice, this looks good.  Let me try this and see how it goes...

I tried Dmitry's patch on Intel Stratix10 platform and it works.

I added one minor change on the top of Dmitry's patch, since I think we 
need add one additional check prior to device_add_groups(). To align 
with Dmitry's patch, I also change my code to use the new dev_groups 
pointer in the struct of device_driver.

My changes are below,

diff --git a/include/linux/device.h b/include/linux/device.h
index 6717ade..9207aea3 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -296,6 +296,7 @@ struct device_driver {
        int (*suspend) (struct device *dev, pm_message_t state);
        int (*resume) (struct device *dev);
        const struct attribute_group **groups;
+       const struct attribute_group **dev_groups;

        const struct dev_pm_ops *pm;

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 994a907..a91e69f 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -554,9 +554,19 @@ static int really_probe(struct device *dev, struct 
device_driver *drv)
                        goto probe_failed;
        }

+       if (drv->dev_groups) {
+               if (device_add_groups(dev, drv->dev_groups)) {
+                       dev_err(dev, "device_add_groups(%s) failed\n",
+                               dev_name(dev));
+                       goto dev_groups_failed;
+               }
+       }
+
        if (test_remove) {
                test_remove = false;

+               device_remove_groups(dev, drv->dev_groups);
+
                if (dev->bus->remove)
                        dev->bus->remove(dev);
                else if (drv->remove)
@@ -584,6 +594,12 @@ static int really_probe(struct device *dev, struct 
device_driver *drv)
                 drv->bus->name, __func__, dev_name(dev), drv->name);
        goto done;

+dev_groups_failed:
+       if (dev->bus->remove)
+               dev->bus->remove(dev);
+       else if (drv->remove)
+               drv->remove(dev);
+
 probe_failed:
        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
@@ -1114,6 +1130,8 @@ static void __device_release_driver(struct device 
*dev, struct device *parent)

                pm_runtime_put_sync(dev);

+               device_remove_groups(dev, drv->dev_groups);
+
                if (dev->bus && dev->bus->remove)
                        dev->bus->remove(dev);
                else if (drv->remove)


diff --git a/drivers/firmware/stratix10-rsu.c 
b/drivers/firmware/stratix10-rsu.c
index 98d8030..93b44e9 100644
--- a/drivers/firmware/stratix10-rsu.c
+++ b/drivers/firmware/stratix10-rsu.c
@@ -391,9 +391,9 @@ static int stratix10_rsu_remove(struct 
platform_device *pdev)
 static struct platform_driver stratix10_rsu_driver = {
        .probe = stratix10_rsu_probe,
        .remove = stratix10_rsu_remove,
        .driver = {
                .name = "stratix10-rsu",
+               .dev_groups = rsu_groups,
        },
 };

Regards,
Richard

> > diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> > index 0df9b4461766..61d9d650d890 100644
> > --- a/drivers/base/dd.c
> > +++ b/drivers/base/dd.c
> > @@ -515,9 +515,17 @@ static int really_probe(struct device *dev, struct device_driver *drv)
> >   			goto probe_failed;
> >   	}
> >   
> > +	if (device_add_groups(dev, drv->dev_groups)) {
> > +		printk(KERN_ERR "%s: device_add_groups(%s) failed\n",
> > +			__func__, dev_name(dev));
>
> dev_err() of course :)
>
> thanks for the review, much appreciated.
>
> greg k-h